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P AUL I NA WO J C I E C H O WS K A
BUILDING WITH EARTH
A Guide to Flexible-Form Earthbag Construction
Copyr i ght 2001 Paul i na Woj ci echowska.
Unl ess ot herwi se not ed, i l l ustrati ons and phot ogr aphs copyr i ght 2001 Paul i na
Woj ci echowska.
Ti tl e page phot ogr aph i s used court esy of Har t wor ks, Inc.
Extract on page xi is f r om Eco Design Journal, vol . 3, no. 3, 19 9 5.
Al l ri ghts reserved. No part of thi s bo o k may be t ransmi t t ed i n any f or m by any
means wi t hout per mi ssi on i n wr i t i ng f r om the publ i sher.
Pri nted i n the Uni t ed States.
First pri nt i ng, June 2001
04 03 02 01 1 2 3 4 5
Pri nted on aci d-f ree, recycl ed paper.
Due to the vari abi l i ty of l ocal condi t i ons, materi al s, skills, site, and so f orth, Chel sea
Green Publ i shi ng Co mpa ny and the aut hor assume no responsi bi l i ty f or personal
i nj ury, pr oper t y damage, or loss f r om acti ons i nspi red by i nf or mat i on i n this book.
Al ways consul t the manuf act urer, appl i cabl e bui l di ng codes, and the Nat i onal El ectri c
Code. Whe n i n doubt , ask for advi ce. Rec ommendat i ons i n thi s bo o k are no
substi tute for the di recti ves of prof essi onal cont ract ors, equi pment manuf act ur er s, or
f ederal , state, and l ocal regul atory officials.
Ma ny of the desi gnat i ons used by manuf act ur er s and sellers to di sti ngui sh thei r
pr oduct s are cl ai med as t rademarks. Whe r e those desi gnati ons appear i n thi s bo o k
and Chel sea Green was aware of a t r ademar k cl ai m, the desi gnat i ons have been
pri nt ed i n i ni ti al capi tal l etters.
Li br ar y of Congr es s Cat al ogi ng- i n- Publ i c at i on Dat a
Woj ci echowska, Paul i na, 19 67 -
Bui l di ng wi t h earth: a gui de to f l exi bl e-f orm eart hbag const ruct i on/
Paul i na Woj ci echowska.
p. c m. (A Real Goods sol ar l i vi ng book)
Incl udes bi bl i ographi cal references and i ndex.
I SBN 1-8 9 0132-8 1-0 (alk. paper)
1. Earth const r uct i on. I. Ti tl e. II. Series.
TH1421 W59 7 2001
69 3' . 9 1dc2i 2001028 67 6
CHELSEA GREEN PUBLI SHI NG COMPANY
Post Office Box 428
White River Junction, VT 05001
(8 00) 639 -409 9
www.chelseagreen.com
I dedicate this book to all my teachers in the world of
natural building, and I thank each one of you for all the
tremendous knowledge and help: Trevor Garnham of Kingston
University, who taught me throughout most of my architectural
education and whose idea it was to write this book; Nader Khalili
and Illona Outram of Cal-Earth, the pioneers of earthbag
Superadobe construction; Athena and Bill Steeen of the
Canelo Project; Tom Watson, the silent inventor of,
among many things, Pumice-crete; and all the others
whom I met on the way who taught me
and took great care of me.
C O N T E N T S
Acknowledgments ix
Introduction xiii
1. EARTH ARCHI TECTURE 3
Clay-Based Building Materials 5
Adobe 6
Cob 8
Rammed Earth 9
Wattle and Daub 10
Straw-Clay 10
Papercrete 11
Earthbags 12
When Are Earthbags Appropriate? 16
Extending or Recycling the
Building 17
Earthbags Forever 19
2. USING BASIC STRUCTURES
FROM NATURE TO BUILD
WITH EARTH 21
Arches 22
Making the Arch 24
Vaults 24
Apses 26
Domes 26
Corbeling 26
3 . G E T T I N G S T A R T ED : D ES I G N,
S I T I NG, A N D F O U N D A T I O N S 2 9
Design Considerations 29
Locating the Building on the
Land 29
Landscaping 30
Topography 30
Orientation 31
Utilities 32
Building Shape 32
Planning Ahead 33
Site Preparation: Setting Out 33
Foundations 34
Earth-Filled Tires 39
Rubble or Mortared Stone 39
Gabions 40
Dry-stone 40
Pumice-crete 40
4 . B UI L DI NG WI T H E A R T H B A G S 4 3
Materials 44
Tools 46
Preparing the Fill 49
Filling Bags or Tubes 50
Filling a Bag with More than Three
People 51
Filling Bags or Tubes with Only
One to Three People 52
Using Small Bags 52
Tamping 52
Keying 54
Structural Reinforcement and
Buttressing 54
Openings 57
Arched Openings 58
Square Openings 60
Bond Beams 60
5 . R O O F S 6 5
Brick or Adobe Roofs 66
Vaulted Roofs 67
Conventional Roofs 68
Water-Catchment Roofs 68
Thatched Roofs 68
Living Roofs 70
Low-cost Flat Roofs 71
Roof Insulation 72
6 . WE A T H E R P R O O F I N G A N D
F I NI S HES 7 5
Earthen Plasters 76
Application 77
Stabilization and Alternatives 78
Vegetable Stabilizers 81
Animal Products as Stabilizers 82
Mineral Stabilizers: Lime 82
Lime Plasters 83
Making Lime Putty (Slaking) 84
Making Lime Plaster or Render 86
Application 87
Pozzolanic Additives to Lime
Plaster 87
Stabilization for Waterproofing 88
Stabilization with Cement 89
Application of Stabilized Renders 91
Interior Finishes 92
Sealants 92
Paints 94
Clay Slip or Alis 95
To Cook Wheat Flour Paste 96
To Make Alis Clay Paint 96
Application 97
Lime Paint or Whitewash 97
Additives to Lime Wash 97
Recipes for Water-Resistant
Whitewash 97
Some Old Limewash Recipes 98
Casein 98
Recipe for Interior-Exterior
Casein 99
Application 100
Oil-Based Paints 100
Maintenance 100
7 . O T H E R I N T E R I O R W A L L S ,
F L O O R S , A N D F U R N I S H I N G S :
B U I L D I N G W I T H C L A Y 103
Finding and Analyzing Building
Soils 103
Jar Test 104
Testing by Hand 105
The Right Mix 105
Thin Partitions and Ceiling
Panels 109
Insulation 110
Straw-Light Clay 111
Hybrid Earthbag and Straw Bale 113
Interior Detailing 114
Earthen Floors 115
Construction 118
Sealants, Maintenance, and
Repair 119
Electricity and Plumbing 120
8 . T H E E A R T H B A G
A D V E N T U R E 123
Shirley Tassencourt's Domes,
Arizona 123
Allegra Ahlquist's House, Arizona 127
House Built by Dominic Howes,
Wisconsin 128
Sue Vaughan's House, Colorado 130
Carol Escott and Steve Kemble's
House, the Bahamas 131
Kelly and Rosana Hart's House,
Colorado 135
Kaki Hunter's and Doni Kiffmeyer's
Honey House, Utah 140
The Lodge "Njaya," Malawi 142
The New House of the Yaquis,
Mexico 143
Afterword 148
Bibliography 149
Resources 153
Index 158
A C K N O W L E D G M E N T S
I would like to give special thanks to Nader Khalili and Iliona Out ram, Bill
and Athena Steen, and Tom Watson for their generosity in everything they
gave t hroughout the many mont hs of my travels, which enabled me to write
this book.
I would like to express my gratitude to all those who helped me put this
book together in many different ways, some of whom I ment i on below:
From Kingston University, I would like to t hank the Green Audit
Research Project for partly funding and enabling me to commence the
writing of this book. Thanks to Peter Jacob, Bryan Gauld, and Sue Ann Lee.
Also to Trevor Garnham for guiding me through the process. From the
Green Audit room at Kingston University: Cigdem Civi, Helen Iball, and
David Lawrence.
Friends in England whose help was invaluable: Flora Gathorne Hardy for
her help, photographs, and immense support and belief in this book; also to
Salim Khan, Bruce Ure, and Shahnawaz Khan for their technical support;
and to Tim Crosskey, Henry Amos, Wasim Madbolly, and Max Jensen for
the photographs; and to Adrian Bunting for the Malawi project.
Friends who contributed their stories and photographs in the United
States: in Arizona, Bill and Athena Steen, also Allegra Ahlquist, Shirley
Tassencourt, and Dominic Howes, who shared information as well as huge
amount s of love and support t hroughout the whole process, together with
Carol Escott and Steve Kemble, and a very big thank you for being there in
those very difficult times. In California: Michael Huskey. In Colorado: Kelly
and Rosana Hart. In Utah: Kaki Hunt er and Doni Kiffmeyer. In New
Mexico: Joseph Kennedy.
Also I would like to t hank Ian Robertson in California for his support,
Gene Leon for early editing, Frank Haendle in Germany for communica-
viii
tions, Lydia Gould for all the survival help in Mexico, and Athena and Bill
Steen for making that trip possible.
It is impossible to name all the people to whom I am very grateful, who
were so wonderful t hroughout my travels, but I would like to quickly
ment i on some not yet named, who looked after me and helped me to make
my journeys: Simon Clark, John Jopling, Vanita and Alistair Sterling, Heidi
Koenig, Catherine Wanek and Pete Fust, Satomi and Tom Landers, Kat
Morrow, Karen Chan, Carole Crews, Cedar Rose, Lynne Elizabeth,
Cassandra Adams, Leonard Littlefinger, Lance Charles, Ralf and Rina
Swentzell, Arin Reeves, George Mohyla, Doc Clyne, Giovani Panza, Craig
Cranic, Michael Smith, Elizabeth Lassuy, Reto Messmer, Kevin Beale, Stokely
Webster, Monika Falk, and Christina and Markus Lehman.
Wi t hout my family, who provided me with constant help and support,
the "journey" and the writing would have been more difficult. I would like
to t hank my parents, Marcjanna Sojka and Krzysztof Wojciechowski, and my
stepfather, Witold Sojka.
My special thanks are extended to my partner, Christof Schwarz, who has
endured many absences and who has provided constant support, encourage-
ment, and help with writing this book, for which I am immensely grateful.
Finally, my thanks to the publishing team at Chelsea Green, especially
Jim Schley, Hannah Silverstein, Ann Aspell, and Rachael Cohen, who have
carefully edited the text, illustrations, and photographs.
... being surrounded by beauty allows one to put aside at least some of the burden of his
or her defences against the world and to feel inwardly free. What relief! What therapy!
Unlike composition, harmony and so on, beauty rules. It is something the artist must struggle
to achieve. And anyone who undertakes this struggle, with all the single-minded dedication it demands,
is an artist. This love force shines from the finished product. It has nothing to do with fashion or style,
and little to do with latent ability. It comes from the gift of love, and an environment
so filled has a powerful healing effect,for love is the greatest healer, needing
only understanding to complete it.
Christopher Day, from "Human Structure and Geometry"
X
I N T R O D U C T I O N
I
had a wishto be able to go to any
place on this Earth and build a shelter
with the materials available to me
from the surrounding environment. I had
already learned about building with wood,
stone, clay, straw, lime, and many combi-
nations and permutations of all these. The
material that would fill in the gap, that
would give me the complete confidence
that I would be able to build a house al-
most anywhere, was sand.
I spent most of the impressionable
years of my life in Afghanistan and India,
where I was surrounded by indigenous ar-
chitecture. It was during that time, I sus-
pect, that I developed a passion for hon-
esty, modesty, and harmony in design. All
the way through my architectural studies,
I was drawn to what I call "primitive" ar-
chitecture. By "primitive" I don't mean
backward, but quite the opposite. To be
primus means to be the first, to be at the
beginning: primary. It is good for the mind
to go back to the beginning, because the
beginning of any established human activ-
ity is often its moment of greatest wonder.
The original forms can teach us the fun-
damental principles of each invention,
showing us the possibility that we might
take a path other than the so-called mod-
ern way.
Most primitive buildings were con-
structed by an anonymous builder in re-
sponse to such conditions as climate, ori-
entation, and the availability of building
materials. Building materials dictated the
form of each structure. The builders were
sensitive to their materials; they worked
with them, not against them as so much of
today's architecture seems to do.
A few years ago, I was working in an ar-
chitectural office. I was always at the draw-
ing board doing technical drawings, not
really understanding the materials I was
working with or why they were used. How
were critical decisions made? Did the best
choices depend on cost, aesthetics, or sur-
roundings, or was the process driven by
people who were just stuck in their ways,
dictating by convention and code how
buildings should be designed? In time, I
realized that to find another way I had to
learn by using my hands. It was necessary
for me to experience actual construction, a
time of very basic building. Always start
with the basicsthe first principle of
natural building.
An opportunity came up to participate
Facing page: Earthen
structures at Cal-Earth,
California.
xiii
in a workshop for people who wanted to
learn to build. It was to be three intense
weeks of building a house for the Othona
Community Retreat in Dorset, England.
The course was run by Simon Clark of
Constructive Individuals, an organization
in London that offers training to people
who wish to build their own homes or ex-
tend or alter an existing dwelling, or who
simply want to have the building process
demystified. How wonderful this oppor-
tunity sounded, to build a whole house in
just three weeks! I jumped at the chance.
The course covered construction tech-
niques and also raised many ecological is-
sues. This particular home was designed to
have minimal impact on the environment
by using recycled-newspaper insulation, a
composting toilet system, solar electric
modules, a graywater system, and a leach-
field to nourish fruit trees. There it all was,
and it had a name: Ecological, Sustainable,
and Environmental. These were the words
used for the simpler ways of building I had
dreamed of. I knew that after this work-
shop I would know what to ask for. A whole
new world was opened to me.
After the Dorset course, I became much
more confident in handling tools, and
many of the mysteries behind building a
house were gone. I had finally experienced
what it felt like to build. I got to "feel" the
materials, feel what concrete is like, feel
what working with wood is like, and learn
how all the pieces go together. I also expe-
rienced the harsh realities of building,
which is exactly what I needed after all
those years at the drawing board. It was
great! These experiences reinforced my
need to go away to places where people
were building using basic principles and
materials, places that would give me more
opportunity to discover indigenous build-
ing materials and techniques, freed from
the rigid commercialism of London archi-
tecture.
In the autumn of 1 9 9 6 , I finally em-
barked on my long-awaited journey. My
first three-month stop was at the Califor-
nia Institute of Earth Art and Architecture
(Cal-Earth). Set up by Iranian-born archi-
tect and author Nader Khalili and his Brit-
ish associate Iliona Outram, this school
takes people on apprenticeship retreats for
a week or more. During this time, Cal-
Earth and its associates contributed to
teaching me of the "magic" simplicity of
earth architecture. Working with the earth
empowered me to carry on, as it has em-
powered many other individuals. I learned
the basics of earthbag construction (called
Superadobe at Cal-Earth) and spent time
researching this method, trying to push its
limitations and explore its possibilities.
To simplify is the aim. What a joy to
learn and to fulfill my dreams! I spent a
wonderful three months, studying as well
as building my own retreat. For the first
time in my life I could design and build a
house with no restrictions from anyone. I
was free and I felt free and therefore I ex-
pressed freedom.
I NTRODUCTI ON
The author's earthbag retreat before plastering.
The author's retreat during plastering.
Here is an extract from my diary, describing my thoughts when
I first arrived at Cal-Earth:
It's early morning as I step outside the house. Mist covers the
bottom of the mountains, silhouettes of shabby Joshua trees, a
tree that stands so still all the time. The sand is lit up, the
mountain towers above the mist. The cold is sharp, the sun is
bright. In the foreground I see domes and desert architecture,
like sand dunes. The landscape looks and feels right. Instead of
destroying the view of the mountain beyond and Joshua trees
around and the vast openness, the structures enhance the view.
I do not feel disturbed by their presence. Quite the opposite; I
am happy they exist and have become an integral part of this
landscape. I walk toward them, at first looking around the
outside. I realize that they are sunken into the ground. They
feel very solid and permanent. Yes, they have this permanence
and belonging about them, a permanence that a timber house
does not have. Once I walk inside, they feel cool. They have
soaked up the night's cold air. I am drawn toward the one that
looks like an animal. It has a fireplace and a small niche to hide
in. Ideas flow into my mind of a house I would like to build
right now for myself, with a network of rooms all interconnect-
ing, partly underground. The outside is very intriguing as well.
I imagine patterns forming from the way the plaster has been
applied and outlined. After a while, I proceed to the other
attractive-looking earth shelter. This one is totally covered in
earth, or so it appears. It has tiny circular windows going all
around at the lower level, great for children if they want to look
out. The light at sunrise is amazing; it floods in though one
larger window. Because of the partially white wall, the room
looks bright. The primitive paintings on the wall stand out.
The light covers the horizon; the sun is a little higher, but the
air is still sharp. I sit in the sun's rays to warm myself.
After some time I get up and walk into a brick dome. The
light beautifully percolates through the bricks. The top of the
dome is open. This one feels the coldest so far, probably
xiv XV
Interior of the author's
Earthmother Dwelling
retreat.
because none of the openings are
glazed, and I feel the air moving
through. I walk to the center. The
acoustics are amazing. The sounds that
I make with my feet bounce around
and seem very loud. What a great place
to play music this would be. After a
short pause, I proceed to the Three
Vault House. Whoa! Rectangular
rooms, white wallsit feels like a
chapel. A lot of different-sized open-
ings and niches in the walls. A cooling
tower under construction. A very large
space in comparison to the others. The
light reflects off the walls in a soothing
way. It feels airy and open. There are
more buildings here than I expected
but what did I expect?
My desire to build using the earth, uti-
lizing the earthbag technique, was very
strong. There were many reasons for this,
including a longing to research an un-
known material, to understand and cel-
ebrate its possibilities. I also wanted to find
out what it takes for a woman with few
manual skills and little strength to build
single-handedly a shelter for herself and
her children. I wanted to indulge in the
freedom of using earthen materials, hav-
ing learned about the structural form of
the arch, which allows the use of only
earthbags for the whole structure, with no
reliance upon wood.
My passion for the arch as a structural
form has little to do with the ways sym-
metrical domes or vaults have been used
traditionally, for example in Islamic archi-
tecture. Rather, this passion has to do with
the prevalence of arched forms in nature. I
did not necessarily want to imitate nature.
I wanted to experience the freedom that
nature appears to possess. I had experi-
enced so many constraints in the world I
came from that I wanted to escape rules
and regularity. I wanted to become free.
So my ideas just came as I went along.
Later, looking back, I could translate these
ideas into theories about design and con-
struction, but that is not how it started.
The accompanying drawings and photos
give a sense of how I went about designing
and building the retreat.
To begin with, I spent many days look-
ing around the site thinking about where
to place my tiny retreat. I found a lovely
spot, away from other structures. A lonely
Joshua tree stood in a clearing of sorts. I
wanted to be close to the tree, having it in
front of my courtyard, with the entrance
facing east, because the strong winds came
from the west. I wanted the retreat to pro-
vide a place to sit facing the courtyard and
the Joshua tree.
When planning the retreat, I tried to
figure out what I would like inside it, never
restricting my imagination. I knew that
people who stayed here would need a place
for their luggage, a place to sleep, and per-
haps a place for a child to sleep. So I de-
signed for a couple and their child. A fire-
place would be used to keep warm and to
cook on. Then I thought of the views, the
light, sunrise and sunset, and the lookout
I NTRODUCTI ON xvii
points for observing who was approach-
ing. The seating areas were to be niches so
three or four people could sit facing each
other. And a child who lay sleeping in a
niche would be able to see the fire burning
opposite, for comfort. I wanted the ceiling
to be high, since we often judge a space by
its volume. Although the main room was
only 10 feet (3 meters) in diameter, ten
people could sit comfortably inside with-
out feeling claustrophobic.
An earthbag dome sunken into the
ground creates and encloses a space. Bas-
ing your design upon that central enclo-
sure, you can add or take away as you
please and as the structure allows. Building
with earthbags is not like digging a cave,
scraping away at the earth to hollow out
the shape of the building, and it's not like a
wooden or concrete house where every-
thing has to be precisely placed to accom-
modate manufactured materials. Building
with earth, you can add as well as remove
material to create the shapes you desire.
The earthbag allowed me a great deal of
freedom. I wanted to celebrate this. As I
worked with this totally fluid material,
earth or sand in bags, I wanted the materi-
als to lead me. I did not want to make it
imitate another kind of building. I wanted
to set the dome free, to listen to it. I was
building with love, creating something
that felt right. I believe that all buildings
should be designed and built with sensi-
tivity. To me, love has become the most
important factor in designing. In fact, I
now see that designing and building are
like sculpting. When sculptors carve rock,
they listen to the rock telling them what it
needs to become. Designing and building
a dwelling is likewise about understanding
the material, the needs and passions of the
inhabitants, and the climate and other
characteristics of the site. The challenge is
to be in harmony with your environment,
and most of all to feel passion during the
process.
To me this is what contributed to my
retreat's soul.
From the moment I started to build, I
recognized that it was essential to main-
tain trust in the material. Without this to-
tal trust, you fall back upon narrow ideas.
To push any process forward, you need
trust. Unless you build with feeling, you
will not feel true contentment with the fin-
ished product. When you merge the natu-
ral and the human-made environment
into one, when you listen to the sun and
the wind and the natural forces all around,
East
xvi
the building can be an organic extension
of the land and the outcome of a marriage
between wind, sun, and the soul of the one
who dwells there.
At the moment, my ideal house is one
that lives in such harmony with its envi-
ronment. It is a house that is difficult to
notice, like an animal that blends into its
surroundings. So many houses appear like
warts in our landscape. When you drive
through the countryside, how much nicer
it would be if you couldn't see the houses,
if they blended in harmoniously, like the
houses that climb the hillsides in Afghani-
stan, made of the same earth as those hill-
sides. Only at night, when the lights come
on, do you see the extent of the develop-
ments.
In building my "Earthmother Dwelling
Retreat" at Cal-Earth, these are some of the
sensitivities that I brought to the process.
In this book, I will give a thorough in-
troduction to earthbag construction and a
basic introduction to some other forms of
"alternative architecture." You have to un-
derstand that this is a drop in the ocean. I
can only introduce the concepts, sharing
some of the lessons I have learned and
sights that I have seen. Numerous books
have been written on many of the natural
construction techniques, some of which
can be ordered from the organizations
and bookstores listed in the resource sec-
tion. However, to my knowledge, no one
has written a book-length work about the
earthbag construction technique, only
short articles for various magazines. This
was my primary reason for putting pen to
paperto provide some of the theoretical
knowledge that I gathered in the places to
which my research took me. That theoreti-
cal foundation is necessary to begin con-
struction, but the reader must remember
that no amount of theory can teach as
much as your own hands. Happy experi-
menting!
B U I L D I N G W I T H E A R T H
xviii
The author (in
foreground) with lliona
Outram (behind) and
other Cal-Earth visitors
inside the Earthmother
Dwelling.
E A R T H A R C H I T E C T U R E
S
ince the earliest times, people have lived in the earth, taking
up residence in existing structures or forming and sculpting
earth around them according to their needs. In terms of
growth and development, indigenous communities usually lived
within the limits of their ecosystems. Nature, technology, and cul-
ture maintained a balance.
Until the industrial revolution, most of the world's people
housed themselves in earthen architecture (Khalili 1986,58). Even
today, it is estimated that a third of the human population lives in
houses constructed of unbaked earth. But, during the industrial
age, the use of engines and fossil fuels expanded the limits of local
ecosystems. Resources from distant regions were brought together
in the process of mass production. Industry on an unimaginable
scale transformed the landscape, while the goods manufactured
on assembly lines transformed our values. Yet for a long time the
environmental consequences of modern design seemed remote. At
the beginning of the twentieth century, architects were inspired by
machinery, not by nature. Modernists saw buildings as isolated ob-
jects, not as part of larger systems or communities. The designs of
the industrialized world have developed to depend on materials
and technologies beyond the limits of what local ecosystems pro-
vide. It may seem as if technology has given people the freedom to
override the laws of nature. But if we use that freedom, we must
take responsibility for making these choices. Today, our global
technologies are depleting the Earth's resources, darkening the
water and skies with waste, and endangering the diversity of life.
Can we find a way of life that will re-create a balance between na-
ture, humanity, and technology?
Above: An afternoon snooze in the city of Petra,
Jordan.
Facing page: The ancient city of Petra, Jordan, carved
out of sandstone.
3
1
Today, timber, steel, and cement are not
readily available in many parts of the
world. They must be transported from
thousands of miles away. For the people
who live in those regions, it would make
more sense to build their own houses out
of what is "beneath their feet" and to use
the materials within their reach. Yet in the
less industrialized countries, where mod-
ern building materials are used by the privi-
leged few, poor people often look down
upon the ancient construction methods
and scorn the earth as a building material.
In response to this, some designers and
builders, including the late Egyptian ar-
chitect Hassan Fathy, have attempted to
revive ancient techniques, building earth
houses for the poor as well as for the rich.
Earth has been used to build on moun-
tains, cliffs, marshlands, and the harshest
of deserts. With a suitable mix of ingredi-
ents and appropriate design, earth can be
used to build almost anywhere in the
world. Why not continue to use earth and
other natural materials where it is appro-
priate to do so?
One of the reasons for the revival of
earth architecture and for the sudden rise
of interest in alternative ways of building is
the change in people's level of conscious-
ness. A growing movement to promote
"natural," "environmental," "sustainable"
understanding is now trying to make
people aware of the devastation that we
have caused on our planet. Among those
designers and builders involved in build-
ing houses, the use of local materials is
becoming increasingly important, among
many other environmental aspects. Using
local materials not only saves energy and
resources, it gives builders and dwellers a
sense that they are grounded, a sense of
belonging, which is missing when "for-
eign" materials are used. In the southwest-
ern United States, for example, the Pueblo
people have traditionally used adobe, a
sun-dried clay brick, because sun and clay
are easily acquired and worked with. In the
northeastern United States, houses were
traditionally made of wood, not because
clay wasn't there, but because wood was
plentiful and easily available. In England,
particularly in Devon, cob was the popular
building material, as the soil was perfect
for forming the loaf-shaped lumps that
constitute the basic building block in this
method. Sadly, people have almost stopped
building earth houses in England, now
that bricks and concrete are cheap and
available.
In the United States today, builders are
gradually returning to older and more
natural construction techniques. People
are learning from ancient European earth-
building traditions such as cob and wattle
and daub, as well as from the traditions of
the Pueblo Indians adapted from the
straw-clay adobe building technique that
was brought by the Spanish a few centuries
ago. New methods, such as straw bale and
earthbag construction, which combine the
benefits of a variety of traditional tech-
EARTH ARCHI TECTURE
niques with elements of modern technol-
ogy, permit people to build dwellings that
are appropriate for the sites and climates
where they are built. It is beyond the scope
of this book to provide detailed descrip-
tions of each natural building technique,
and the books listed in the bibliography
provide more comprehensive information
on adobe, cob, rammed earth, straw bale,
and other methods. Here I will give brief
introductions to several traditional tech-
niques that are especially useful in combi-
nation with earthbag construction.
C L A Y - B A S E D
B U I L D I N G M A T E R I A L S
A critical ingredient in durable, resilient
earth for building is clay. In response to
cultural, climatic, and geographical differ-
ences throughout the world, many varia-
tions of clay-based earth architecture have
been developed. These techniques can be
traced back thousands of years; for ex-
ample, traces of mud walls from more
than two thousand years ago were found at
the Tel Dor excavations in Israel (Stern
19 9 4) 133) . Parts of the Great Wall of China
are built out of earth and are still standing
today. In many cultures, clay has long been
considered a magical material. It is written
in holy books and poems that humans
themselves were created from clay.
In the Pueblo cultures of the American
Southwest, one of the deities is the Pueblo
Clay Lady, who is said to live in each piece
of clay pottery made in the traditional
manner: She inspires and advises her pot-
ters what to do while working with clay.
There is a Tewa prayer, of which the
Santa Clara Pueblo poet and potter Nora
Naranjo-Morse says (Swan & Swan 1 9 9 6 ) ,
"This prayer continually renews our rela-
tionship to the earth, her gifts, and [the
people]."
Clay Mother,
I have come to the center of your
adobe,
feed and clothe me
and in the end you will absorb me
into your center.
However far you travel,
do not go crying.
Clay is the result of the chemical weath-
ering of rock and silicates such as feldspar,
quartz, and mica. The diameter of clay
grains is smaller than two one-thou-
sandths of a millimeter. There are several
types of clay, but the most commonly
found are kaolin and montmorillonite.
With an electron microscope, one can see
that these materials are wafer-thin, foli-
ated, and scaly crystals.
Earth alone (without the use of forms)
can be used for construction only if it con-
tains some kind of stabilizing element,
which in industrialized architecture is of-
ten cement. In traditional natural build-
ing, we use clay as the binding material,
due to the cohesive properties of the clay
molecules. These molecules are attracted
4 5
to each other, therefore producing a strong
bond. If clay particles are well distributed
throughout the soil, they form a coating
around the particles of silt, sand, straw,
and gravel or other filler used, effectively
binding them together.
On drying, the swollen clay shrinks un-
evenly and causes shrinkage cracks. The
more water that is absorbed by the clay, the
larger the cracks will be after drying. Each
type of clay has a different chemical com-
positions, but above all they vary in their
water-absorbing qualities. Kaolin absorbs
water the least, while montmorillonite can
absorb seven times as much water, and can
swell to sixteen times its volume. Working
the clay with your hands enables the clay
particles to pack together in denser, paral-
lel layers, creating stronger binding force.
As a result, the tensile and compressive
strength is greater, up to 20 percent more
than in mechanically compressed blocks.
Many different types of traditional earth
construction require some clay as the
binder for cohesion, including adobe, cob,
rammed earth, wattle and daub, and
blends of clay with straw or other fibers.
Because of serious, building-related envi-
ronmental problems in industrialized
countries, in recent years we have seen a
dramatic revival of traditional building
techniques based on clay. Clay is non-
toxic, recyclable, and easily available in
many parts of the world. Combined with
sand, gravel, and natural fibers such as
straw and wood, clay is again becoming
popular as a base for interior and exterior
plasters and construction materials. This
is largely due to cost and energy savings,
and to the way that houses built with clay-
based materials are more aesthetically
pleasing and healthier to live in, especially
for chemically sensitive individuals.
See chapter 7 for more detailed infor-
mation about working with clay as a build-
ing material.
A D O B E
Adobe blocks are sun-dried mud bricks
that can be stuck together with mud mor-
tar to create thick walls. They have been
used for thousands of years in North Af-
rica, South America, Asia, and the Middle
East, and were brought into the southwest-
ern United States by the Spanish. The
Spanish learned about adobe construction
from the Egyptians, who still use this an-
cient building technique. Using the arch,
dome, and vault, it became possible to cre-
ate houses using only earth (Fathy 1 9 8 6) .
Many magnificent large adobe structures
are still in use in Africa, Asia, and the
Middle East.
While in most of the world's countries
adobe is used for the poor, in the south-
western United States it is increasingly
fashionable with the very rich to live in a
healthy, natural house. Because adobe is
very labor intensive, it is very expensive to
pay someone else to build and finish an
adobe house. But, because the materials
the earth at your feetare practically free,
EARTH ARCHI TECTURE
7
it is very inexpensive to build with adobe if
you do the work yourself.
The Taos Indians of New Mexico have a
long tradition of earth building using
adobe. Adobe houses are part of the cul-
ture of the Pueblo people. They go to-
gether like Eskimos and igloos. During the
persecutions by the Spanish and by the
Americans the adobe walls protected the
Pueblo people and allowed them to keep
many of their spiritual beliefs, attitudes,
and practices to themselves.
The beauty of earth architecture is that
it participates in the natural environment.
It is part of a continuous cycle, unlike con-
temporary industrialized architecture,
where structures are built to stand inde-
pendent of and unaffected by their sur-
roundings. Build, live and die, build, live. . .
Adobe houses, like other earth houses,
have to be cared for continuously and
when their useful life is over, they are given
the respect of being allowed to melt back
into the earth. For example, a house is
boarded up after the death of its owner.
New people moving in will mold new ado-
bes from the material remaining, and the
cycle will continue.
Adobe structures flow out of the earth,
and it is often difficult to see where the
ground stops and the buildings begin. By
using adobe to build the walls of a house
and cob to sculpt the interior, beautiful,
curved forms can be fairly quickly con-
structed that provide very inviting living
space while also providing the mass
Adobe houses in Taos Pueblo, New Mexico.
or adobe houses to live on we have to take care of them, like
you would take care of a child. You coat the child, we plaster
the adobe houses, so they can stand up. When you live in a
house the house is almost like a part of you because you live in it and
it lives with you. When you keep the house warm it will keep you
warm. If you die the house will also die with you. When you build a
house, you build the house with what you're actually standing on.
Once upon a time there might have been a house there also, but the
recycling of the adobe material is almost like building what had been
there once upon a time.
J oe Martinez, Taos Pueblo,
quoted in At Home with Mother Earth
(Feat of Clay, 1995)
6
needed for a building to perform well thermally. Ovens and seat-
ing as well as walls can be created using adobe finished with an
earthen plaster. (See chapter 7 for more discussion of how to use
adobe in conjunction with other earthen techniques.)
The traditional method of adobe preparation is a highly labori-
ous process. The strength and durability of the finished dwelling
depends upon the quality of the bricks. Adobe bricks are produced
by putting the appropriate soil, clay, and straw mixture into a mold
where the mix is worked lightly by hand then quickly removed. The
mold must be clean and wet to ease removal of the formed brick.
Adobes can also be made without forms, but a large quantity of
mortar must be used to smooth out the unevenness of the joints.
Adobe is sometimes criticized for being a very soft material, but
adobe construction is a system. That is, no single brick is subjected
to intensive pressure, because the overall wall, which is stronger
than its individual parts, carries the weight of the roof. To add to its
strength, adobe can be reinforced with a diversity of fibers.
C O B
Cob is like an adobe mix with as much straw as the mud mixture
can accept before it fails to bind. That is, subsoil containing clay is
mixed with straw and water and brought to a suitable consistency
by kneading or treading. The lumps of earth (or "cobs") are then
placed in horizontal layers to form a mass wall. The bulk of a cob
structure does not always consist solely of cob mixture. Cob that
contains gravel or rubble can be sculpted into walls, making the
whole structure more resistant to moisture, allowing more air to
circulate inside, and keeping it drier.
Cob was traditionally a popular building material in the west-
ern parts of Britain, mostly Devon and the southwestern regions,
because the soils of that region are among the best in Britain for
earth construction. Most soils there contain a good proportion of
clays that are fairly coarse and therefore do not expand and con-
tract extensively and which provide adequate cohesion. Secondly,
these soils are usually found to contain a well-distributed range of
aggregates, from coarse gravel to fine sands and silts. A good, well-
EARTH ARCHI TECTURE
9
graded subsoil mixed with plenty of straw
requires no other additives to make good
cob for building.
The durability of a cob house depends
on how much energy is put into it as well as
what is in the mix. If a cob walls fails it is
usually not the fault of the material but of
the builder. Like adobe houses, if the cob
house is loved and cared for it will last for
a long time.
R A M M E D E A R T H
This is another age-old technique that uti-
lizes only the earth to create thick, durable
walls, which can be load-bearing, low-cost,
heat-storing, and recyclable. Rammed earth
structures can be built in a variety of cli-
mates and will last for hundreds of years.
The construction procedure is simple. A
mixture of earth is rammed between
wooden forms. The forms are removed,
creating thick walls that need no external
finishes. The most basic type of rammed
earth structure can be made if a minimum
of 5 percent clay is present to bind the soil
and if wood or other material is available
to make temporary forms.
Rammed earth is another ancient
earth-building technique currently being
revived in many parts of the world. The
Great Wall of China is partially built out of
rammed earth, and this technique has
been used in Yemen to build structures as
high as seven stories. In eighteenth-
century France, a pioneering architect
named Francois Cointeraux tried to revive
rammed earth construction with little
success due to fear of competition among
other builders. Currently in France, the
use of earth as a building material is being
revived by the organization CRATerre. In
Cob fireplace sculpted
by Kiko Denzer at the
Black Range Lodge,
Kingston, New Mexico.
Rammed earth house in Arizona.
Adobe house of Hassan Fathy, Egypt.
A boy making adobes in Peru.
8
Australia, it is a popular alternative build-
ing technique, and its modern application
in the United States has been pioneered by
David Easton, who updated Cointeraux's
techniques with improved engineering,
sophisticated forms, and innovative design
to make rammed earth cost-competitive
with conventional construction. Modern
equipment speeds the process. The soil is
mixed on-site and then poured into the
wooden forms set up on top of an appro-
priate foundation (usually stone or con-
crete). An earth mixture with a moisture
content of 10 percent is then rammed in 6-
to 8-inch layers using pneumatic or hand
tampers. The forms are removed, reveal-
ing a 2-foot-thick wall that is then com-
plete. A concrete bond beam is poured for
the top of the wall on which the roof will
sit. Even at its simplest, rammed earth re-
quires more complex technology than
adobe or cob but can be used to raise mas-
sive walls in a shorter period of time
(Easton 1996).
W A T T L E A N D D A U B
In Britain, wattle and daub was widely
used in the construction of internal walls
and ceilings and also for external walls of
houses. Wattle-and-daub panels in tim-
ber-framed houses were in common use
until the eighteenth century.
The wattle (branches) act as support for
mud plaster (daub). Oak or other timber
stakes are installed vertically into a frame
woven out of willows or other flexible
wood and covered with a heavy mixture of
A wattle panel under construction.
clay and straw. When dry, the surface can
be plastered with a mixture of lime, sand,
and animal hair and painted with white-
wash. Chapter 6 describes lime plasters
and finishes for use on any earthen wall.
S T R A W - C L A Y
Straw-clay is the general term used for any
building material that is made out of straw
and clay (with some sand to reduce crack-
ing and increase mass) but does not fit into
the traditional adobe or cob category. Al-
though the mixture can be very similar to
adobe or cob, the main difference is the
greater quantities of fiber. If the binding
clay is diluted with more water to a creamy
liquid consistency prior to mixing with fi-
bers, it becomes "light clay." The most
popular uses of straw-clay mixes include
straw-clay blocks (straw coated with light
clay rammed into formwork), thin interior
or exterior walls reinforced with bamboo
or branches, ceiling infill between beams
or floors, or straw-clay panels for thermal
or acoustic insulation. Higher density of
straw allows for better insulation for roofs,
floors, or the insulating layer on an
EARTH ARCHI TECTURE
11
Advantages of Addi ng Fiber
Some of the many advantages of adding
fibers such as straw to an earthen mix are:
controlling the shrinkage cracks
increasing tensile strength
improving insulation value
There are also many advantages of coating
natural fibers wi th earth:
increasing compressive strength
providing fire resistance
improving water resistance
improving insect resistance
earthbag wall. Other combinations of fi-
ber, clay, and sand are probably being de-
veloped, as the possibilities are endless. See
chapter 7 for more detailed discussion of
straw-clay mixtures.
Earthen materials and natural fibers
work together extremely well, preserving
and protecting one another, and combin-
ing the earth's thermal mass with the
fiber's insulative value. Bill and Athena
Steen, who have been using straw-clay
techniques in Mexico, have said "they can
be built from predominantly local materi-
als in whatever combination best matches
the local climate. Like the rest of life, build-
ing can be much more fulfilling when
founded on a good relationship. For us,
. . . combining earth with natural fibers has
led to an unfolding of options and possi-
bilities that would not be open to us if we
were to remain simply straw bale builders."
The main disadvantage of adding fiber
to an earthen mix is the reduction in the
material's thermal properties. The more
straw, the less thermal mass the structure
will have. This is only a disadvantage if the
surface is needed for passive solar heat gain
or cooling, in which case less straw and
more sand can be added to the mixture.
P A P E R C R E T E
"Papercrete," or "fibrous cement," is an ex-
perimental technique recently reinvented
independently and pioneered by Mike
McCain in Alamosa, Colorado, and Eric
Patterson of Silver City, New Mexico.
Papercrete is a type of industrial-strength
Straw-clay block
construction of the
office headquarters for
the Save the Children
Foundation in Cuidad
Obregon,Mexico.
Straw-clay can be used
to make large blocks to
construct whole walls,
wall or ceiling infill
between framing or
floors, large ceiling
panels made by
inserting bamboo or
branches as
reinforcement, or even
rolls and arches.
papier-mache used to make large blocks to
construct houses as well as a plaster for
covering them. It has been successfully
used in earthbag projects as a thick plaster.
If applied in several 2-inch ( 5 0 millimeter)
layers, papercrete will contribute to the in-
sulation value of an earthbag house. Ac-
cording to Gordon Solberg in an Earth
Quarterly special issue on paper houses
(see the bibliography), papercrete's R-value
is 2. 8 per inch. When dry, papercrete is
lightweight, holds its shape well, and is
remarkably strong. Papercrete is also du-
rable when wet, although not waterproof,
and in very damp climates will need to be
sealed with a waterproof layer. For in-
stance, a coat of tar has been used success-
fully as waterproofing on top of a paper-
crete structure in Colorado.
To make papercrete take a large mixing
container and soak old newspapers and
magazines until they are soft. Mix in ce-
ment or lime and sand for greater strength.
The recipe for the papercrete plaster mix
Kelly and Rosana used on their house (see
chapter 8) is as follows:
First coat (more insulative): 1 part
paper to 1 part cement + water
Second coat (more waterproof): 1 part
cement to 1 part lime to 8 parts sand
+ water
To make papercrete blocks for con-
struction, Gordon Solberg recommends
mixing together a "soup" of 60 percent pa-
per, 30 percent screened earth or sand, and
10 percent cement. This mixture is then
poured into forms to make blocks and can
also be used as a plaster or mortar.
In Adobe Journal (nos. 12 & 13) Mike
McCain described a procedure for making
large quantities of papercrete. Fill a tank
with water and add magazines and news-
paper. Start mixing, and when the mixture
turns into a slurry, add 8 to 9 one-gallon
buckets 2/3 full (or 6 shovels-full, approxi-
mately) of sandy soil that has been sieved
using chickenwire to eliminate larger
rocks. Then add one 94-pound bag of ce-
ment to the mix. The amount of water
needed can be estimated by watching as
the cement is absorbed by the paper fibers.
Be sure that the water is evenly distributed
thoughout the mix, as any excess water will
separate. By weight, 20 percent of the mix-
ture should be one-half sand, one-quarter
paper, and one-quarter cement, and the
remaining 80 percent of the mixture
should be water.
Mike has devised a faster and easier way
of mixing by mounting a barrel with an
overturned lawnmower blade in the bot-
tom above the axle of a cart. He uses a drive
shaft to turn the lawnmower blade when
the wheels of the cart turn. The mixer can
be towed behind a car or truck, or even a
horse.
E A R T H B A G S
Earthbags are textile bags or tubes filled
with earth (sometimes sand or gravel),
rammed to a very solid mass, then used to
construct foundations, walls, and domes.
EARTH ARCHI TECTURE
This method of construction is rising in
popularity among natural and alternative
builders, especially in the United States.
This technique is essentially a flexible-
form variation of rammed earth. The bags
are permanent forms that allow you to
ram or tamp the earth to create thick
earthen walls, symmetrical arches, vaults,
or domes, and freeform landscape fea-
tures; and to sculpt forms the way a potter
molds coils of clay, blending your struc-
ture into the landscape.
The earthbag technique requires few
skills and tools other than a shovel, and
can be used on almost any land, in any lo-
cation. When built properly, earthbag
walls are extremely strong. They are most
advantageous in remote areas with no
wood for a frame and no clay for a cob or
adobe building, since the use of bags as a
container allows the builder to utilize a
wide range of soils, from unstabilized
earth or sand directly from the site to soils
with a high clay content, or even gravel. As
a result, costly materials such as cement
and steel can largely be avoided. Earthbags
can even be used in areas prone to flooding
and periodic wet conditions.
If an arch is used as the primary struc-
tural elementfor example, a dome for
the central structure with self-supporting
arches for openingsno wood is neces-
sary in the construction, thereby avoiding
the deforestation so widespread in the
United States and around the globe.
Earthbag buildings are low in materials
cost, but intensive in labor, albeit less labor-
intensive than adobe, cob, or rammed
earth. Earthbags can be used in areas with
limited technology and low income, but
where people are willing to work on con-
structing buildings for themselves. The
bags are cheap and easily transported, so
this technique can be used for disaster-
relief housing.
Sketch view.
Plan
Interconnected spaces can be arranged in response
to the site and solar exposure.
Roof plan.
1 2
An earthbag "dome" is rounded overall,
but not necessarily symmetrical. The height
of the dome proportionally exceeds its di-
ameter. The difference between earthbag
domes and the high-tech geodesic domes
invented by Buckminster Fuller is that
earthbag domes can never have large
spans. An earthbag house can be anything
from a single dome to a whole village of
domes interconnected by vaults. Arched
openings can form entrances into other
spaces, niches, and apses. If a large earth-
bag house is desired, many domed struc-
tures can be built, each one joined to the
next using a small vault. New openings can
be easily cut out and extra rooms added as
required. Such structures grow organi-
cally, each addition buttressing the next
one. Chapter 2 explains the principles of
arches, domes, and vaults that you will
need to know to build these structures
with earthbags.
Through recent history, sandbags and
earthbags have been used for varied pur-
poses, mostly in emergency relief work, for
example to provide erosion or flood con-
trol, when filled with earth or pumped full
of concrete or soil cement, then used for
fast construction of embankments. Earth-
bags have also been used by archaeologists,
to aid in structural support of collapsing
walls; by armies, to create bunkers and air-
Structural and Seismic Testing
B
etween 1993 and 1995, three of the experimental earthbag structures at Cal-Earth passed
structural tests approved by the International Conference of Building Officials (ICBO),
leading to a building permit for the Hesperia Museum and Nature Center in California in
March 1996, the first to be granted under the California Building Code for earthbag construction.
A school initially designed by Nader Khalili and lliona Outram in Nevada is currently under
construction wi th code approval (Outram 1996).
The tests carried out for the ICBO included a live-load test and dynami c and static-loading
tests. For some of the tests, cables were wrapped around three buildings of different designs, and
hydraulic jacks were used to pull 3,000 pounds of cumulative pressure every 15 minutes. Nader
Khalili explains, "On our superadobe prototype we went from 3,000 to 26,000 pounds of conti nu-
ous stress and held it there for hours. This was beyond any required code for any building within
fifty miles. The inspectors found no cracks or movement, so now this method is approved for all
types of buildings, from residential to commercial." (designer/builder J une 1996.)
In high wi nd and earthquake areas, symmetrical buildings tend to be less heavily damaged.
The form of a dome is more likely to absorb an earthquake's jolts and spread the shock equally
through the structure, and the wei ght and curve of a dome deflects winds, allowing them to
EARTH ARCHI TECTURE
raid shelters; and by landscapers, to create
free-form retaining or enclosure walls.
According to J. F. Kennedy (1999, 82),
German architect Frei Otto experimented
in the 1960s with using earthbags for
building. In 1978 a team from the For-
schungslabor fur Experimentelles Bauen
(FEB), the Research Laboratory for Ex-
perimental Building at the University of
Kassel in Germany, led by professor, archi-
tect, and author Gemot Minke (Lehmbau-
Handbuch, 1997), set up an experimental
earthbag project. This experiment was fol-
lowed by a joint research project spon-
sored by the FEB, the Center for Appropri-
ate Technology (CEMAT), and the Univ-
ersidad Francisco Marroquin in Guate-
mala, which attempted to develop an
earthquake-proof system. Long cotton
tubes, dipped in lime wash to prevent the
bags from deterioration, were filled with
volcanic earth (pumice) and stacked be-
tween bamboo poles, serving as a proto-
type for a single-story house. The poles
were tied with wire every fifth course and
fastened to the foundation below and a
bond beam above, creating movable but
earthquake-resistant walls. Further re-
search was carried out by Minke at the
university through extensive experiments
with earth-filled sacks and tubes to create
various structures, including domes.
wrap around the building rather than lifting it (Muller 1993). By contrast, vaults have a very poor
earthquake resistance. This is due to the torque oscillations in structures, caused by the strong
increase in seismic accelerations transferred from the terrain to the founda-
tions when at different levels the centers of gravity do not coincide wi th
the centers of torsion (Houben and Guillaud, 313). For seismic areas,
Nader Khalili has devel oped a foundation system where the base of
the dome is isolated from the slab it sits on by a layer of sand,
therefore enabling the structure to move freely during an earth-
quake, (see chapter 3 for more on foundations).
Above: In 1993 the sandbag and barbed wire system was analyzed at Cal-Polytech, San Luis Obispo, where
testing included observations on a scale model on a seismic table (Outram 1996,58). The earthbag structures
tested were constructed out of unstabilized earth, with barbed wire between each course, an adobe plaster
finish inside and outside, and metal strapping loosely netted about the structure to contain bursting forces. The
intersections were riveted or bolted together, and four zones of diagonal "X" strapping were added for
resistance to shear forces (Kennedy 1994, 19).
14 15
16
An experimental dome
at Cal-Earth, has stood
for five years without
interior plaster. Though
the polypropylene
bags have degraded
from ultraviolet light,
the compacted earth,
which has a low clay
content, is falling apart
as could be expected.
The recent trend in using earthbag tech-
nology in building homes is largely due to
the pioneering work carried out by the
Californian Institute of Earth
Art and Architecture (Cal-
Earth) in the Mojave Desert,
which was set up by Nader
Khalili, Iranian-born architect
and author, who calls his build-
ing technique "Superadobe."
Since 1 9 9 0, the team at Cal-
Earth, in collaboration with
the city of Hesperia and many
researchers and associates, has
been investigating earthbag
construction and developing
its applications, from straight
walls to domed structures. To
satisfy a desire (or even an ob-
session) to avoid wood, they
have managed to create stable dome-
shaped structures using the corbeling
method (see chapter 2) . This means that
with no materials other than bags, barbed
wire, and local earth, you can build your-
self a shelter anywhere in the world.
Many people who have attended work-
shops at Cal-Earth have started to spread
their knowledge. The first fully function-
ing and lived-in earthbag dome was built
in Arizona for Shirley Tassencourt by
Dominic Howes, who went on to build
other round, domed, and straight-walled
or square earthbag houses and water-stor-
age tanks. Many others have followed, in-
cluding a domed structure built in Utah by
Kaki Hunter and Doni Kiffmeyer of OK
OK OK Productions; a three-vault house
built by Cal-Earth apprentices in Sar-
miento, Mexico; a development built by
Mara Cranic in Baja California; a two-
story house, the ground floor constructed
of earthbags and the first floor of timber,
built in the Bahamas by Carol Escott and
Steve Kemble of Sustainable Systems Sup-
port; a hybrid earthbag and pumice-filled-
bag house built by Kelly and Rosana Hart
of HartWorks; and Joseph Kennedy's ex-
perimental work in South Africa with bags
containing high proportions of clay, ce-
ment bond beams, and bag additions to
existing structures.
Earthbags are also becoming popular
among natural builders as foundations,
filled with gravel, sand, and/or earth, be-
neath straw bale and cob buildings. Earth-
bag structures can range from emergency
refugee housing for the poor to elaborate,
modern residences complete with plumb-
ing and electricity.
W H E N A R E E A R T H B A G S
A P P R O P R I A T E ?
The bags are used only as a temporary
formwork for ramming the earth, before
the plaster is applied. It is actually the plas-
ter that should be considered a permanent
enclosure or casing. The materials used to
fill the bags can range from very loose
gravel, pumice, or sand to a more com-
pactable soil, which might contain varying
amounts of clay. The weaker the fill mate-
EARTH ARCHI TECTURE
17
rial (meaning it contains little binding
strength such as clay) the stronger the bag
material must be. If the soil has a high clay
content, bags might not be necessary to
contain the earthen mixture (see the dis-
cussion of soil testing in chapter 7 ) . In that
case, other construction techniques such
as adobe or cob might be more appropri-
ate. When earthbags are used, especially in
flood areas, care must be taken that the
lower courses of the wall do not contain
clay, which wicks moisture. If the higher
courses contain clay, they need to be
tamped or rammed well to reduce the like-
lihood that insufficiently compacted clay
will absorb moisture.
E X T E N D I N G O R R E C Y C L I N G T H E
B U I L D I N G
It is helpful to plan for future extensions of
an earthbag building during the initial de-
sign stage in order to prevent awkward re-
design problems later and to avoid the
need to rethink all the openings and utili-
ties. For example, anticipating a future
opening by building an arch in that loca-
tion and filling it in with nonstructural
earthbags or another material such as
straw bales or straw-clay mixture can save
much time when you decide to cut
through the original wall to make an addi-
tion. But if the earth in the bags is
compactable and not just pure sand,
which will simply spill out when the wall is
breached, it is also possible to make open-
ings later if really necessary. The plaster-
work can be hacked off, exposing the bags.
Cut the bags with scissors or a scalpel, and
scoop out the hard, rammed earth. The
bags can then be resealed using nails like
tailor pins or sewn together with wire, and
the plaster reapplied. This is a time-con-
suming process, and care must be taken
that the opening cut out is in the shape of
a steep arch for structural stability (see the
discussion of openings in chapter 4 ) . If a
square opening is cut out, the opening will
not support rows of bags above. Square
openings must therefore be the height of
the whole wall. Better yet, plan ahead and
build in arched openings that can be ac-
cessed later by removing the finish plaster.
The cheapest and most flexible option is to
plan future extensions at the outset. Do
not be afraid to start small and expand
later.
An earthbag structure can also be com-
pletely recycled. If the bags were filled with
pure earth from the land the building is
standing on, once the structure is no
longer maintained the walls will begin to
turn back into earth after a few decades,
especially if biodegradable burlap bags
were used. If polypropylene bags are used,
they will only biodegrade if exposed to the
sun's ultraviolet light once the protective
earthen plaster deteriorates, which it will
do over time without regular recoatings. If
an earthbag structure is dismantled prior
to the polypropylene's disintegration, the
bags as well as the earth inside can be re-
used for a new building.
TLHOLEGO LEARNI NG CENTRE, SOUTH AFRI CA
T
his prototype was designed by
J oseph F. Kennedy and constructed
using burlap sacks and soil-cement
plaster, a concrete bond beam, and a brick
dome roof.
The walls were built using burlap sacks
filled wi th the earth from the site, whi ch
had a high clay content. These were well
tamped to achieve compacti on. The bond
beam was poured on top of the wall to
whi ch the brick dome woul d be fixed. The
first row of bricks to the brick dome was
hollow, allowing the insertion of reinforcing
rods and anchor bolts to anchor the dome
to the bond beam. The structure has
buttresses for added stability and was
plastered wi th soil cement. Sawn bags were
also used for shade on the trellis.
Detail of the earthbag house prototype showing the brick domed roof and buttresses.
External planters, also constructed using earthbags.
EARTH ARCHI TECTURE
E A R T H B A G S F O R E V E R
Many regions in the world, including the
desert regions of North Africa, the Middle
East, and the southwestern United States,
do not have abundant supplies of wood,
stone, or clay. In Egypt, for example, the
traditional construction material was
adobe made out of clay taken from the
flood plains of the Nile. Now clay is in
great demand, and therefore more expen-
sive to acquire. To be able to build with or-
dinary sand or unstabilized earth could
benefit many people.
Of course, unlike adobe or cob con-
struction, where the earth used contains
clay as a binding element, the sandbag or
earthbag technique requires a source of
bags, but in most places, cloth is an acces-
sible commodity. These bags can be made
out of absolutely any cloth, even old
clothes cut up and modified to hold earth.
The bags are only there to hold the earth in
place before plaster can be applied, unless
the shelter is needed only for a year or two,
in which case the bags can be left exposed
and allowed to deteriorate in the sun.
Another great advantage is that sand-
bags have long been used to control floods
and erosion in many areas. This demon-
strates the strength and durability of these
walls, suggesting that this material would
be perfect for flood areas and disaster re-
lief. The aerodynamic shape of domed
houses that integrate into the landscape,
shaped like mounds or hills, might better
withstand strong winds and hurricanes,
providing another advantage of these in-
expensive shelters.
Ultimately, my love for the earthbag
technique also comes from the simplicity
of the construction process. There is no
saw or nails in sight, just bags and earth.
There is no need to lift heavy loads, be-
cause the earth is carried to fill the bags in
place. Any child or adult could build them-
selves a house!
18
19
U S I N G B A S I C S T R U C T U R E S F R OM N A T U R E
T O BUI LD WI T H E A R T H
T
o be able to build out of earth
alone, we must understand certain
basic structural principles. To me,
the most important structural element,
the key to all earth construction, is the
arch. This was one of my earliest and most
exciting discoveries concerning earth ar-
chitecture, as the arch is a form that occurs
all around us in nature, which allows us to
build strong, resilient structures without
high-embodied-energy materials such as
timber, concrete, or steel. An arch can be
used to form the curved or pointed upper
end of an opening (as in a window or door)
or a support (as in a truss or bridge); this
shape is strong and stable because gravity
pulls equally on each part, and each part
supports the weight of the parts above.
Most naturally occurring caves incor-
porate the arch in their structure. Also,
animals that make dwellings in the earth
use this form to prevent their homes from
collapsing. One such example is a colony
of termites building their earth house us-
ing the arch as their main structural ele-
ment to support a network of ducts and
cavities, as described by Lewis Thomas in
The Lives of a Cell:
When you consider the size of an
individual termite, photographed
standing alongside his nest, he ranks
with the New Yorker and shows a
better sense of organization then a
resident of Los Angeles. Some of the
mound nests of Macrotermes
bellicosus in Africa, measure twelve
feet high and a hundred feet across,
[and] contain several millions of
termites. . . . The interiors of the
nests are like a three-dimensional
maze, intricate arrangements of
spiraling galleries, corridors, and
arched vaults, ventilated and air
conditioned.... The fundamental
structural unit, on which the whole
design is based is the arch.
As Nader Khalili has noted in Ceramic
Houses, forms in nature, whether con-
structed or created by natural forces, ex-
emplify efficiency.
Nature generates structures based on
the principle of minimum material,
maximum efficiency. From mol-
ecules, to soap bubbles . . . all follow
Facing page: The first
earthbag dome
attempted at Cal-Earth.
Strapped straw-filled
bags form the upper
part of the dome.
Termites building an
arch. Even though they
work on the opposite
ends, the arch meets in
the center. (After
Woodward 1995.)
21
2
2 2
Sean relaxing in the opening of Allegra's earthbag
garden wall after a hard day of plastering.
Large-span concrete arch, Arcosanti, Arizona.
this general rule . . . a spider's web is a natural structure that
works by ultimate tension, and an eggshell is a structure that
works by ultimate compression. Both use the minimum and
the appropriate material with maximum efficiency.
Over the course of architectural history, the construction of
roofs and openings out of earth alone became a necessity in many
regions where structural timber was not easily available. In Egypt
and the Middle East, among many other places, builders came up
with the idea (no doubt emulating nature) of arched openings and
vaulted roofs to cover the spaces they wanted to inhabit. One can
still visit large spanned domes (a set of arches with a common cen-
tral peak or pivot) and vaults (a series of adjacent arches) in the
Middle East built with adobe that have lasted for centuries. How-
ever, instead of building large spaces and then subdividing them, it
is often more appropriate in earth construction to build several
smaller spaces connected to each other, in order to provide for
structural stability in each element, and to accommodate different
functions, like rooms in a conventional Western building.
This introduction to nature-based architectural forms will
emphasize the primacy of the arch, that singular structural ele-
ment that enables builders to construct arched openings, vaults,
and domes. Once you understand the structural principles of the
arch, you can create a network of variously sized and shaped
arches constellated together to form a variety of useful and beau-
tiful spatial structures. When the arched form is repeated in linear
fashion, it becomes a vault. When an arch is rotated on its central
axis or centerpoint, it becomes a dome. When an arch is laid upon
the ground, then partially raised, diagonal to the ground, it be-
comes an apse.
A R C H E S
A chain hanging between two posts creates an arch form that is
perfectly in tension, because of equal distribution of gravity along
the curves. An arch of this shape is called a lancet or catenary arch.
When you turn this shape upside down, you get a design that pro-
US I NG BASI C STRUCTURES FROM NATURE TO BUI LD WI TH EARTH
23
vides ideal compression, evenly distribut-
ing the downward, compressive forces
along the whole of the arch.
A chain under tension. Chain turned upside down
forms a lancet arch under compression.
In a masonry arch using this form, the
individual bricks are tilted upward at their
outer edges, toward the center of the arch.
Once a keystone is placed in position at the
peak of the arch, vertical force, or gravity,
pushes down, causing the stones to press
against each other and transferring the
load to the ground.
To prevent this downward force from
causing the sides of the arch to kick out
horizontally, thereby collapsing the arch,
buttressing must be added at either side
around the base. The point of greatest
Vertical forces acting on an arch.
Horizontal forces
acting on an arch
horizontal pressure is the point along the
arm of the arch where it begins to curve
toward the center to meet its symmetrical
counterpart, the other arm of the arch.
The imaginary line running between these
two points where the curves commence is
called the spring line. Buttresses should re-
inforce the base of the arch up to this
spring line or higher.
You can calculate the size of the buttress
needed by drawing a model to scale on
paper (see the illustration below). Divide a
curved arch (which could also represent a
vault as well as a dome) into three equal
tangential parts. Project out from Y, using
point X as the center line of a circle and Y
as the end of the radius. Measure from
point Z to determine the necessary thick-
ness of the buttress.
How to determine the
minimum size of a buttress.
Because successive arches function as
buttressing, in older buildings the arch is
often repeated to form vaults, serving as a
structural and decorative element, as can
be seen in old churches and cathedrals.
Other commonly used buttresses are solid
buttresses, parapet-tie wall buttresses, and
Another arch acting as
a form of buttress.
24
solid buttress parapet tie wall tie bars
Construction of a dry-pack arch at Cal-Earth during construction of the Hesperia
Nature Museum.
tie bars. These buttressing systems must be
evenly distributed along the vault and se-
curely anchored in the ground.
M A K I N G T H E A R C H
When learning about the forces of the arch
and the materials that you are working
with, there is no substitute for actually
learning through your hands. You can
make a small dry-pack arch as an experi-
mental exercise. This technique is called
"dry pack" because no mortar is necessary
to hold the arch together. A temporary
supporting form can be made out of ply-
wood, a bucket, or anything else that has a
circular shape. Balance this form on
wedges to ease its removal once the arch is
constructed.
As you position stones or bricks on top
of the form, place shims (small stones or
fired brick) between the outside edges to
ensure that the inside edge of each brick is
perpendicular to the arch form. Pour sand
between the bricks to fill any cavities.
Once the keystone is in position at the
apex or meeting point on top, and the arch
is buttressed, the temporary form can be
removed.
V A U L T S
If you elongate an arch or repeat it in a lin-
ear sequence, the new form created is a
vault. The same buttressing rules apply to
vaults as to arches (see page 23) . A vault is
simply a deep or extended arch. Vaults can
be used to form the passageways connect-
US I NG BASI C STRUCTURES FROM NATURE TO BUI LD WI TH EARTH
ing adjacent domed or vaulted structures.
In Iran, where earthen architecture is an
ancient and ongoing tradition, the most
commonly found span (or width) of vault
is approximately 12 feet ( 3. 6 meters). Ac-
cording to research conducted by the Uni-
versity of Baja California, Mexico, the ratio
of span to length in a vault should be no
Detail of the
permanent
form used in
Obregon,
Mexico.
A repeated arch forms a vault.
more than 1.5 meters times the width. If a
vault is greater in length, there is a danger
that in an earthquake the vault will reso-
nate beyond its capacity to absorb the
shock, and will shatter (Khalili 1986, 57).
Because the walls of a vault are structural,
openings such as windows and doors
should be kept to a minimum.
There are three main methods for con-
structing a vault.
The first is to build over a form, which
can be removed and reused. This is eco-
nomical for small spans, but the cost of
timber to construct the form for a larger
span may be considerable, unless you have
a plentiful local source.
The second method is to use a perma-
nent form, built to become an integral part
of the structure. A good example of this is
in the Obregon project in Mexico (see
above). This form was constructed out of a
bamboolike reed called carrizo, which was
bent over a very simple temporary form
and buttressed at the ends with a concrete
beam. Three layers of carrizo were placed
over each other and were finished with an
insulative straw-clay mix, capped with a
waterproof coating of lime.
Another example that I have come
across of a permanent form for vault con-
struction was in the Hermosillo project
(described in detail on page 1 43) . Rein-
forcement rods were embedded in the
ground at 18 -inch ( 450 millimeter) inter-
vals, then bent into position, and horizon-
tal members were added. An expomat
mesha stretchy metal mesh material
that can be used on corners, damp-proof
membranes, or any areas where plaster
must be applied to a nonstick surface
was then fixed to the underside to hold the
4 inches ( 100 millimeters) of soil-lime or
soil-cement that was applied on top. This
formed a very sturdy structure. The pho-
tographs on page 146 show the strength of
the arch. The reinforcement bars alone,
when bent in an arched shape, could
25
support the weight of a person. Of course,
the materials were not entirely ecological.
The third method of making a vault is
to use no fabricated form, merely earth.
The Nubian vault may be built without
any structural members or formwork, just
using earth-clay-straw blocks or masonry
(Houben & Guilland 1994).
The end wall is built up first. This wall is
either straight or arched. The first brick is
laid at an angle, and others follow suit. The
vault can be started at either or both ends
simultaneously to meet in the middle. For
an in-depth account of this method, see
Nader Khalili's Ceramic Houses.
A P S E S
An apse is a leaning arch. Figuratively, if
you lay an arch on the ground and raise it
at an angle, it becomes an apse. Old cathe-
drals utilized the apse form for rounded
extensions to the central structure, used as
more intimate chapels or sanctuaries.
D O M E S
A dome is an arch that has been rotated on
its central axis to create a group of arches
with a common peak or center point.
As already noted, because of the hori-
zontal forces tending to push the base of
the dome outward, a buttress or continu-
ous tension ring is necessary at the base of
a dome. If an opening is made at the top,
the horizontal forces will be pressing in-
ward, therefore requiring a compression
ring, to prevent the structure from com-
pressing, or caving in.
As with arches, the buttressing for a
dome only needs to provide support up to
the spring line. The buttress can either be
constructed along the outside, or the dome
can be sunken into the ground so that the
ground itself will act as the buttress.
A tension ring. A compression ring.
Note: A tension ring can be created out of concrete
with continuous reinforcement (rebar) at the base of
the dome. A compression ring at the top is
necessary only if there is an opening.
The ground acting as a buttress and a buttressed
dome.
C O R B E L I N G
An alternative to the dry-pack arch dis-
cussed on page 24 is the corbeled arch. Cor-
beling involves constructing the arch in
such a way that the units (bricks, stones,
earthbags) lay flat, but each is stepped in-
ward so that the weight is evenly distrib-
uted along the arc of the arch, as shown
opposite.
Like the corbeled arch, corbeled domes
are erected by building inward on succes-
US I NG BASI C STRUCTURES FROM NATURE TO BUI LD WI TH EARTH
27
An angled masonry arch or dome. A corbeled arch or dome.
sive horizontal courses. This is the principal used in sandbag con-
struction; because the bags have no mortar to bind them and the
sand is a fluid form, they cannot be placed at an angle. An earthbag
dome could be constructed with the earthbags at an angle if there
were a form underneath, but for a dome this could be very expen-
sive to construct, given the amount of material required; therefore,
angling is only practical when constructing arches. Earthbag
domes must be corbeled.
To build an earthen dome on top of a square-shaped structure,
squinches need to be constructed first. A squinch forms the transi-
tion from square into circle. Any shape with even sides could have
a dome constructed above. A square is turned into a circle by cre-
ating four squinches in the four corners. In this way, a dome can
serve as a substitute for a conventional truss or rafter structure.
Once you understand the "arch principle," there is no limit to
the shapes that you can create, and there is no need to be bound by
the conventions of rectangular architecture or even by symmetry.
To Determi ne Thickness of a Shel l :*
Radius
< 500
Thickness
Radius of dome divided by the thickness of the shell should not
exceed 500.
* From Philip Vittone."Dome and Vault Engineering," Adobe Journal 12 & 13 (1997): 56.
A spiral corbeled brick dome under construction at
Cal-Earth under Nader Khalili's supervision.
26
3
GETTING STARTED:
DES I GN, SI TI NG, A N D F O U N D A T I O N S
W
hatever materials are used,
there is no single "right" way
to design a house, as land-
scapes differ, climates differ, cultures dif-
fer, and the needs of residents differ. Before
finalizing any decisions, research all the
options that are available to you. One way
of doing this is to take the conceptual de-
sign to a very detailed stage to actually
gauge what materials will be needed and
how the various elements will go together.
Design is a process of asking yourself ques-
tions, which requires knowing what ques-
tions to ask.
D E S I G N C O N S I D E R A T I O N S
Before looking carefully at site preparation
and foundations specific to earthbag con-
struction, let us consider the basic design
considerations that pertain to any kind of
construction, emphasizing the value of
doing as much of the design as possible by
yourself. By carrying out the design your-
self or in close collaboration with some-
one who is more experienced, you can
maintain control of the materials, keeping
construction costs to a minimum and the
complexity of the construction within the
range of your own skills. You will also gain
a sense of self-reliance by learning your
way through the process.
Locating the Building on the Land
Whatever type of structure you want to
build, however large or small, it is impor-
tant to place it in the context of its sur-
roundings so that it belongs to the land, as
an integral part of the landscape. Spend as
much time as possible on your intended
site, preferably during all four seasons,
observing where the sun rises and sets, the
direction of the wind, the views. Consider
the neighbors, and the simplest routes for
access, snow removal, power, water, and
sewage.
As much as possible, work around ex-
isting elements of the landscape such as
trees and boulders. Try to minimize the
damage that you will inflict on the land
with even the smallest of houses. Plan to
replace any vegetation that you cannot
avoid destroying. Try to retain the "spirit"
of the place, which is the result of this
locale's unique qualities and features. You
might want to leave the most distinctive
areas of your land completely untouched,
Facing page: Apse and
dome of the Hart's
pumice-bag house in
Colorado.
29
30
so they retain their natural beauty and you
can enjoy them outside the sphere of your
house. Good design will help you mini-
mize your impact on the land, to satisfy
both the human occupants and the wild-
life, ideally enhancing rather than disrupt-
ing the natural energy flows in the sur-
roundings, creating balance and harmony.
Landscaping
The landscaping around your house is just
as important as the design of your house.
Locate the house in such a way that sun-
light to your flower or vegetable garden is
not blocked by any part of the building. To
be sure that the garden is accessible and
inviting, create an easy path to it from your
kitchen. If you are building with earth, you
can sculpt retaining walls, benches, a bread
oven, or a grotto for gathering out of the
same earthen materials used to construct
the house. Creating bridges between out-
side and inside is a crucial part of building
the house.
Topography
Go to your local building department to
obtain historical flood reports and other
information regarding your land. Choose
a higher location that is protected from
runoff during heavy rains, or build ap-
propriate drainage, contour swells, retain-
ing walls, or gabions to rechannel runoff
around the site to planted areas. Observe
Bui l di ng in Flood-Prone Areas
If your land has a history of flooding and you plan to build
using earthbags, you could build your house in such a way
that the main living area is on a higher level, wi th the
lower level providing a foundation of bags filled wi th
permeabl e gravel or perhaps an earthbag basement
wi th good drainage for runoff. To prevent wicking
of moisture from lower to upper sections of
the walls when water is standing in the
lower part of the house, the walls should
incorporate a moisture barrier to
separate the solid-packed
An earthbag dome for flood areas.
Bags below flood level are filled
with gravel to prevent capillary
rise of moisture. Note also
the waterproof layer
separating the lower from
the upper courses.
damp-proof course
flood level
DES I GN, S I TI NG, AND FOUNDATI ONS
31
what happens on neighboring sites during
heavy rains. Talk to your neighbors about
weather patterns and their experiences on
the land.
Building on a hilltop increases the po-
tential for erosion. Consider wind expo-
sure and the aesthetic consequence for
your neighbors' view if you build on a
high, exposed site. Show the same respect
to your neighbors that you would like
them to show for you. Remember, from
nature's point of view, most of the time the
best house is no house.
Sandbags are very often used in flooded
areas, and the same technology is viable in
a house, where instead of merely using the
bags as a barrier to water, they can be used
for constructing a flood-resistant founda-
tion or first story (see diagrams on facing
page.)
Orientation
Consider the location of all windows in
relation to the sunwhere it rises and sets,
the winter and summer angles, and the
shade cast at different times of year by sur-
rounding hills, trees, or other existing or
potential buildings. If you live in an area
that is sunny but has cold winters, adopt a
passive solar design to take advantage of
the winter sun. Especially in cold climates,
avoid building on dark, damp northern
slopes. (See the bibliography for recom-
mended books explaining the principles of
passive solar siting, design, and materials.)
Use seasonal screens to create covered
patios in the summer that will be exposed
in winter to let the sun's rays reach your
home. Deciduous trees planted on the
east, south, and west will provide shade in
the summer but drop their leaves in the
winter, allowing more sunlight to reach
the house.
Carefully consider the materials of the
building's interior. Earth or stone walls on
which the sun's rays fall can absorb and
store heat in order to give it back at night.
Such walls have thermal mass, which evens
out temperature fluctuations, retaining
the night's cool to keep rooms cooler dur-
ing the following day, and retaining day-
time heat to keep a home warmer even on
cool nights. Earthen walls can be beneficial
in either hot or cold climates.
summer
If you live in a cooler area, you will want
to shield your house from cold winds. This
can be done by positioning the building
below a hilltop or behind dense trees and
Orientation of the
house toward the
south provides passive
solar heating in the
winter. Overhangs limit
solar gain in summer.
earthbags above from
those containing gravel to
facilitate drainage.
32
by landscaping so that foliage or other bar-
riers provide protection. Locating a mini-
mum of windows on the windward side
can also help considerably during those
windy winter days.
If you are building in a hot and humid
climate, it is important to position the
house in the path of the prevailing breezes.
If heavy trees block the wind's path, it is
good to raise the house and expose it to
the breeze, with openings that go right
through the house (see Steve and Carol's
house, profiled on page 131) . In the hot and
dry climates of the Middle East, cooling
traditionally has been achieved by con-
structing cooling towers that direct mov-
ing air right into the living spaces. Also
plan for overhangs to prevent too much
sunlight entering the house.
Utilities
At the earliest stages of planning, identify
the location of any existing utilities, and
consider what services you may need in
the future, including a spring or well, cis-
terns for harvesting rainwater, and gray-
water and septic systems for processing
wastes. In many countries, it is now viable
to live "off the grid," providing your own
electricity, heating and cooling, and hot
water with solar or wind energy. With ac-
cess to a year-round stream, you may even
be able to harvest hydroelectricity with a
microturbine sized for household needs.
Even in locations where the winters are
cold and long and hours of daylight are
short, heat that comes free from the sun
can result in significant cost and energy sav-
ings. As emphasized above, a well-designed
passive solar house can be heated almost
entirely by solar gain with a small wood-
burning or fossil-fuel heater as a backup.
Building Shape
Think of your house not just as a shell of a
box or a dome, with all of its useful fea-
tures on the inside. Remember that highly
functional external features such as walls,
porches, and benches provide sun and
shade zones in summer and winter. If your
finish will be prone to erosion from
weather, elements such as landscaping,
overhangs, and seasonal rain- and wind-
screens are essential, as well as splash-back
protection at the base of walls.
Should the house be one large structure
or a cluster of smaller ones either built si-
multaneously or added on as the need
arises? A house does not have to be one
structure. You could start off with the
minimum living space and utilities and
gradually add rooms, guest houses, and
workshops. As the family grows or your
needs change, more rooms or structures
can be incorporated.
DES I GN, S I TI NG, AND FOUNDATI ONS
Think of all the activities that might be
performed inside and outside the house
during all twenty-four hours of the day,
from when you get up in the morning until
the next morning. Try to think of all the
seasonal changes in light, temperature,
smells, insects, the rain and snow, and the
views. The more time you spend on the site
before building, the easier it will be to an-
ticipate its changes. Effective design pro-
cess involves imagining the countless func-
tional and aesthetic possibilities as well as
the limitations of the materials you will be
working with.
Planning Ahead
Position your house to accommodate fu-
ture additions, including outbuildings,
without drastic modifications of the land-
scape. Also consider the ways that future
changes made by neighbors may affect you
over time. If there aren't any neighbors,
plan for the worst (a future neighbor
might build a high building right against
your boundary), and you are less likely to
be disappointed.
As much as possible, it is helpful to
identify and plan your prospective exten-
sions of the house during the design stage
to prevent awkward redesigning and re-
construction in the future. Anticipate the
need for additional services and openings.
If you've planned ahead well, as a family
grows and more rooms are required, these
can be added with minimum cost, so do
not be afraid to start small and expand
later, if necessary.
S I T E P R E P A R A T I O N : S E T T I N G O U T
Precision in the laying out of a building's
base is most important for locating the
foundation in the best possible place. If
the earthbag foundation stem wall will be
short and another building technique will
be used on top of thisfor example, a
straw bale wall, a timber frame, or a roof
type such as a vaulted, flat, or pitched roof
that relies on a level surfaceit's essential
that the foundation provide a level plane.
If you are building a monolithic earthbag
structure, the foundation will be an inte-
gral part of the walls and roof; therefore
the shape and size of the foundation will
follow through the whole structure.
33
34
The site should be cleared and leveled
prior to setting out lines for the founda-
tion and walls. If a conventional rectangu-
lar building is to be constructed, set out
string lines in the traditional manner (see
the diagram on page 33) ; at the corner
points where strings cross, hammer a stake
into the ground. If the strings are placed
level with each other at a specific height,
they can be used as a benchmark to mea-
sure the height of the stem wall or the
depth of the foundation trench.
If you are building on a sloping site, the
strings should be at the same height as the
top of the stem wall.
A circular building or a dome requires a
compass to begin construction. String lines
are not appropriate for this shape. The
compass will be useful in "setting out" or
inscribing the dome, and throughout the
dome's construction. The compass can be
very simple, merely a string or a chain, or
more complex to serve as a guide through-
out the process, allowing the builders to
maintain symmetry as the height of the
structure rises. A more detailed explana-
tion of how to use a compass to maintain
the shape in dome construction will be
found in chapter 4, "Building with Earth-
bags." If organic material is removed, all of
the subsoil taken from the foundation area
can be saved to fill bags.
F O U N D A T I O N S
The functions of the foundation in any
building are to minimize any movement
of the ground over time; to spread the load
of walls and roof evenly in order to give the
DES I GN, S I TI NG, AND FOUNDATI ONS
35
Two scenarios, with good and bad foundation details. On the left, lower bags are filled with gravel, which drains
readily and prevents moisture from deteriorating the high-clay-content wall above. On the right, clay in the lower
courses is worn away by rainsplash,forming cavities.
building a stable base; to hold the building
in one integral unit, especially in earth-
quake areas; and to keep the building dry,
providing a barrier between the walls and
any ground moisture.
The connection of the wall to the
ground is one of the most important de-
tails on an earthen house. When con-
structed poorly, the wall may not last as
long and will jeopardize the rest of the
building. If the foundation is not built
carefully, moisture will migrate up the wall
through capillary action and weaken the
earthen walls and therefore the entire
structure.
When digging the foundation trench, it
is necessary to go down to undisturbed
ground, below the frost heave level to bed-
rock or compressed subsoil, to minimize
any movement caused by the ground.
Once this solid ground is reached, you can
build the foundation using gravel in a
trench or in the bags, to raise the building's
base above ground level, and to prevent
capillary moisture movement. In most
situations, the lower courses of earthbags
should be filled with gravel, up to at least 12
inches (30 cm) above ground level, with
the upper course very level to receive fur-
ther courses filled with earth or any other
material.
When constructing an earthbag build-
ing in a dry area, not prone to excessive
moisture or flooding, it is best to build it
sunken into the ground. This has several
advantages:
the earth that is dug out can be used
for filling the bags;
the ground acts as a buttress;
the building will sit much lower on its
site, so it will be less obtrusive visually,
and less exposed to severe winds and
weather.
When building above ground level, you
will need to provide separate buttressing.
In damp areas, if the fill material for the
wall construction is high in clay content, it
needs a foundation base with either gravel
earth on
the side)
Option 2
In a dry location,
buttressing is provided
by digging a hole so
the building is sunken
into the ground.
Excavated earth can be
used for fill.
Setting out a round base house using a string as a
compass.
A compass designed by Nader Khalili to construct
caternary-shaped earthbag domes for the Hesperia
Nature Museum.
Gravelbag foundation
for slightly damp areas,
without the use of
damp-proof
membrane.
1. Exterior finish: earthen plaster, in damp climates
capped with lime.
2. Interior earthen plaster.
3. Four-poinl barbed wire or branches of a thorny
plant. This creates friction and therefore acts as a
Velcro-type of mortar between the bags. Note: For
added stabilization of straight-wall construction in
earthquake areas, the courses of bags can be pinned to
each other or can be buttressed or sandwiched
between wooden or bamboo posts tied to both the
foundation below and the bond beam above.
4. Bags filled with earth from the site, well tamped. If
the soil contains much clay, it needs to be more solidly
compacted to minimize its"thirst"for moisture.
Compaction of the clay reduces its ability to draw in
moisture and consequently expand.
5. Bags filled with gravel (well tamped) to raise the
structure off the ground, to minimize moisture
migration upward into the wall through capillary
action.
6. Waterproofing: can consist of a layer of clay or any
other waterproofing membrane, or just well-
compacted earth in very dry areas.
DES I GN, S I TI NG, AND FOUNDATI ONS
37
Earthbag foundation
for well-drained areas
with base isolation for
domes and a solid
"pad" or "raft" with
tension ring
reinforcement. Pad can
be pumice-crete, lime,
or reinforced concrete.
Grave] trench and gravelbag foundation.
7. Large stones used for a plaster stop.
8. Well-consolidated, washed gravel in trench, to
prevent capillary rise of moisture.
9. Well-compacted earthen layer. Depth varies
according to requirements (this layer can contain
radiant floor heating, but needs to be the necessary
thickness for effective thermal mass).
10. lnsulation:straw-clay mixture, pumice, or perlite-
clay mixture; depth varies according to climate.
11. Well-consolidated gravel, to minimize moisture
migration upward. Can be larger stones topped with
small gravel. The best gravel is rounded to increase
drainage spaces around the stones.
12. Pumice- or cement-stabilized lower course of bags,
with a continuous ring of reinforcement in earthquake
areas.
13. Drain to collect any water that may be trapped (to
be approximately 1 inches (4 centimeters) off the
base of the trench to reduce blockage.
14. Waterproof membrane.
36
Gravelbag foundation for dry areas.
Earthbag and gravel trench foundation with damp-
proof membrane for slightly damp areas.
Foundati on Details
Wider foundation for straight-walled house with
timber posts tied together with polypropylene or
wire.
Gravelbag foundation and buttress for domes in
fairly dry areas with sandy soils and good drainage.
(Otherwise use perforated drain in gravel trench.)
or "sandy" fill. Otherwise, if the bags con-
taining clay are exposed to water from
flooding or even "splash back," the clay can
expand and break apart the wall or dissolve
and seep out, leaving cavities and resulting
in instability. Alternatively, line the foun-
dation trench with a plastic sheet to serve
as a damp-proof membrane that will pre-
vent moisture in the ground from migrat-
ing upwards into the wall above. Or wrap
each bag in the lower courses individually
in a plastic bag before tamping it into place
(see the description of the Kaki Hunter
and Doni Kiffmeyer project in chapter 8 ).
If the area is not so damp, gravel in the
trench and gravel in the lower courses of
bags will facilitate drainage, minimizing
the movement of moisture upward.
If your house is in an area prone to
flooding, the lower courses might require
stabilization with an additive such as ce-
ment or lime. Better yet, design the house
to alleviate the problem of moisture alto-
gether. For example, you can allow the
water simply to pass through the lower
level. Remember that if the lower courses
are filled with coarse sand and/or gravel,
which drains very readily, the house is not
likely to have its foundation washed out
from underneath (see sidebar on pages
36-37). Be aware that many "bag" materi-
als are subject to decay, and should not be
relied upon to contain nonstabilized fill in
permanently or frequently wet conditions.
To secure the lower course of earthbags
from decay, you may fill the bags with soil
stabilized by cement, or actually with con-
crete, although concrete is expensive, envi-
ronmentally destructive, and its use un-
dermines many of the advantages of using
the comparably inexpensive earthbags as
an alternative.
To construct a foundation with insu-
lative properties, you can tamp the lower
bags full of scoria or pumice and wrap
them with a damp-proof membrane, since
small-sized particles tend to absorb mois-
ture. Alternatively, the pumice can be
mixed with cement to form pumice-crete.
For earthquake areas, Nader Khalili's
solution was to isolate the base of the
structure by laying down a layer of sand
between the foundation slab or the bed-
rock at the base of the building, allowing it
to "float" during earthquakes, "like an up-
side down teacup." This would reduce the
risk of breakage in the walls, as no rigid
pressure points are exerted upward by the
ground.
The diagrams on pages 36 - 37 show sev-
eral examples of foundation details. The
variations are innumerable, as the best so-
lution will differ slightly for each type of
earth, climate, construction material, size
of structure, and budget.
Earthbag or gravelbag foundations can
also be used for other natural wall systems,
including straw bales, rammed earth, cord-
wood masonry, and adobe. Especially in
earthquake regions and when combining
earthbags with straw bale or cob construc-
tion, rebar or other pegs can be pounded
DES I GN, S I TI NG, AND FOUNDATI ONS
39
into an earthbag stem wall for added anchorage, and rubber tub-
ing or metal rods can be left extending from an earthbag founda-
tion to allow for compression of the adjacent bale wall.
Retaining walls can also be built with bags, but it is important to
provide good drainage behind the wall and ensure that bags are
properly secured against slippage. For added stability compact the
bags at a slight angle toward the earth bank. In addition, many
other low-cost foundation systems can be combined with earth-
bag or other wall systems. Following are a few suggestions. Also,
The Last Straw magazine published a special issue on alternative
foundations (no. 16, 1996; see the resources list).
Earth-Filled Tires
This rammed earth technique is similar to earthbags but uses re-
cycled tires as the permanent forms. Soil-filled tires are stacked
like giant bricks to form foundations as well as exterior and inte-
rior walls. To construct a tire foundation, dig a trench down to
frost depth, and place tires, ramming then with slightly moistened
earth, or dig a trench below frost level, fill it with well-consoli-
dated, washed gravel, then level the surface. Place recycled tires on
the gravel and ram them full of moistened earth. Concrete may be
used to fill the voids between tires. Sometimes a concrete sill is
poured into forms on top, with metal anchor bolts embedded for
fastening down the base of the wall above. This method of attach-
ment is not considered adequate in earthquake regions.
Rubble or Mortared Stone
This type of foundation can be made from large pieces of stone or
concrete rubble recycled from old pavement. A trench is dug, then
large rubble pieces are carefully laid on undisturbed ground, with
bent metal rods protruding to provide attachment points between
the wall and foundation. A rubble trench can provide good drain-
age if necessary.
Tires rammed with
earth.
concrete
infill in
voids
metal grips for
wall strapping
stabilized
earth in top
row of tires
Tire foundation
with metal
handles.
Mortared stone/rubble
footing with metal
grips for wall strapping,
if required.
rammed
earth in
tires
38
40
Dry-stone wall.
Pumice-crete stem wall.
Gabions
A gabion is a latticework container woven out of willow or galva-
nized steel and filled with loose stones, often used as a retaining
wall. Like a rubble trench foundation, a gabion will drain away
moisture very effectively, so it can be used below ground as a foun-
dation or partly above ground as a stem wall, isolating an earthbag
wall from the moist ground.
Dry-stone
This type of foundation involves great artistry and requires a gen-
erous supply of relatively flat stones. Many traditional buildings in
stony locales have foundations of this type. Carefully selected
stones are stacked on top of each other in overlapping courses,
resting on undisturbed or well-tamped earth that is below the frost
line or any ground movement.
Pumice-crete
This building technique invented by Tom Watson has spread rap-
idly in areas where pumice is a readily available resource. A very
porous volcanic stone, pumice can be used as the aggregate with a
mix of a little Portland cement and water to bind it together. A
typical ratio is approximately 1 part cement to between 9 and 12
parts pumice, but test samples always need to be made. For greater
strength, for example above doors and windows, use 1 part cement
to 4 parts pumice. Pumice-crete actually uses very little cement
compared with conventional concrete, as the more finely ground
pumice combines easily with cement and adds to its binding
strength. Pumice-crete can be mixed and poured into temporary
or permanent forms. Due to its porosity, it acts as a good insulative
material, needing no further insulation, and also provides thermal
mass.
Rigid temporary forms could be built in the same way as the
formwork used for concrete and removed several days after pour-
ing when the mixture has dried. Permanent forms could be galva-
nized wire, or any type of bags, paper or plastic, that will contain
DES I GN, S I TI NG, AND FOUNDATI ONS
the mixture until it sets. No additional
compaction is needed.
Due to its low cost, high speed of con-
struction, and insulative and thermal
properties, creating very comfortable liv-
ing conditions, pumice-crete makes a
good foundation, and some people are
constructing entire buildings of this mate-
rial. The walls of a pumice-crete house can
be rendered (plastered) or unrendered.
When used for wall construction, the
pumice can be mixed with lime or clay in-
stead of cement, but this will require a
separate foundation to raise the wall above
ground level or a damp-proof membrane
to prevent moisture wicking up into the
permeable wall, which could be damaged
by water dissolving the lime or clay.
41
T
he use of the soil-filled sacks called "earthbags" has in re-
cent years been revived as a building technique, largely
due to the pioneering work of Nader Khalili at the Califor-
nia Institute of Earth Art and Architecture (Cal-Earth). Its popu-
larity is rising for several reasons.
It is low cost in terms of tools and materials, utilizing available
soil in almost any region, and requiring only a few skills that are
easy to learn. The polypropylene or burlap (hessian) bags used to
contain the soil can be obtained free or relatively cheaply. Earthbag
walls go up faster than cob or adobe and are very flexible, unlike
rammed earth, allowing the construction of any shape from very
straight and square structures to free forms and domes. Earthbag
structures can be adapted to any conditions, from regions that
flood to the most desertlike lands. When constructed properly,
they are strong and durable, expected to last for hundreds of years.
And, because the bags are light and easily transported, they are
extremely useful for emergency shelter, in areas that are prone to
flooding, or in remote locations where little or no wood, stone, or
clay is available.
In chapter 2, we looked at the way that builders using masonry
materials can build an arch by angling the bricks or blocks up at
the outer edge, since they can be held in place by mortar, which
dries solid. An earthbag dome cannot be constructed in the same
way as a masonry dome. Due to the fluid properties of earth, each
row of earthbags needs to be laid flat, then corbeled, or stepped
inward with each successive course, in the same way that a dry-
block dome is corbeled. This corbeling makes an earthbag dome
much steeper than a masonry dome. The corbeled earthen dome
43
A brick dry-stacked corbeled dome.
Facing page: The art of earthbag engineering. Steve
Kemble in the Bahamas in 1998.
BUI LDI NG WI T H E A R T H B A G S
4
44
Corbeled earthbag dome buttressed by the ground.
compass point
How to construct an arch of an earthbag dome on
paper.
Sculpture made of burlap bags filled with sand.
takes the form of a lancet arch, as described in chapter 2. If the rows
of bags have been stepped in too fast, the dome will be shallower in
its rise and there could be a danger of collapse.
In this chapter, we will look carefully at the steps involved in
constructing an earthbag structure. Before describing techniques
for filling and tamping the bags that serve as the "building blocks"
in this construction system, I will enumerate the recommended
materials and tools, then review key structural principles includ-
ing the use of tension rings and compression rings, as well as the
importance of corbeling in a domed structure and buttressing in a
straight-walled structure.
M A T E R I A L S
The materials needed for earthbag construction are relatively in-
expensive, very portable, and available nearly everywhere. If you
live in a place where these materials are difficult to find, see the
resource list for suppliers who will allow you to order them for
shipment to your location or use the Yellow Pages to find local
suppliers.
Bags or tubes: The purpose of the bag is to retain the earth during
the construction process. It is a type of permanent form to allow
the earth to be placed in a course and tamped solid. When the
building is subsequently plastered over these bags will no longer
be visible, and will be largely redundant in terms of their struc-
tural function, since the plaster "skin" will contain the earthen
walls. Again, as a general rule, the weaker the mix, the stronger the
bag should be.
Bags can come ready-made or can be bought on a roll and cut
to the desired length on-site (longer bags are called tubes).
Two types of bags are available on the market: burlap (hessian)
and polypropylene, in a range of widths. Both types can be avail-
able in tube form on a roll (usually 1,000 or 2,000 yards per roll),
or already cut up and sewn into bags. Presewn bags are generally
more expensive, unless you can find a source for recycled grain,
seed, or coffee bags or "seconds" with some kind of insignificant
flaw that a manufacturer may be willing to sell cheap.
BUILDING WITH EARTHBAGS
45
The width of the earth-filled bag or tube
after tamping will be approximately 13 per-
cent smaller than the width of an unfilled
bag or tube, and the depth when filled and
tamped will be about 30 percent of the
original bag width.
Burlap is a natural woven fabric that is
biodegradable, and therefore more ap-
pealing to those consciously trying to use
environmentally benign materials. How-
ever, you can only use burlap if the earth is
not pure sand (which will slip through the
weave of the fabric) but contains com-
pressible particles of soil. Burlap bags are
heavier and bulkier than bags made of
plastic, and more expensive to ship. In En-
gland, an 18 -inch-wide tube of hessian
maybe purchased for anywhere from 30 to
50 pence per meter, plus the delivery fee.
The material is delivered in rolls of a few
hundred meters, and may be any desired
width. In the United States, 18-inch burlap
costs approximately 50 to 80 cents per
yard, plus the delivery charge. For an odor-
less, nontoxic material, make sure that you
get hydrocarbon-free burlap bags (Hunter
& Kiffmeyer 2000).
Polypropylene is made of woven threads
of plastic (Richardson and Lokensgard
1989). Polypropylene is a simple plastic
and is not as environmentally toxic as the
infamous polyvinyl chloride (PVC). It is
not biodegradable, although polypropy-
lene bags deteriorate if exposed to ultra-
violet rays, so care should be taken when
storing the material to protect it from di-
rect sunlight. If a building project is not
complete within three months, all exposed
polypropylene bags should be covered in
some type of finish to protect them from
ultraviolet rays.
In England, an 18 -inch-wide tube of
polypropylene costs anywhere from 17 to
40 pence per meter, plus delivery fee. In the
United States, most manufacturers will
deliver a minimum of 1,000 yards at a cost
of approximately 22 cents per yard, plus
delivery fee. See the resources list for infor-
mation on ordering polypropylene tubes
on a roll.
There are cheaper alternatives, if you
are prepared to be resourceful and persis-
tent in tracking down supplies. It is pos-
sible to use recycled bags, which might be
obtained from stores or factories that use
them for bagged produce. "Misprints" are
also available for a reduced price from
some companies that manufacture the
bags, as they sometimes make mistakes in
the printing process that render the bags
unsuitable to their clients. Or you can
make the bags yourself by obtaining inex-
pensive cloth or scraps, preferably mate-
rial that does not tear too easily. Fold the
cloth in half and sew along one side to
form a bag or tube of the desired length. If
the bags are filled with a material of high
binding property such as clay or stabilized
soil, the bags can be removed once set.
Fill: The earth used to fill the bags can be
used as it comes directly from the site, al-
though if it contains too much organic mat-
ter or too many large stones that prevent
As a general rule,
the lower the
binding proper-
ties of the fill, the
stronger the bag
materia! should
be.
Chemical composition
of polypropylene.
Polypropylene tube on
a roll.
good compaction, these need to be sifted
out. The soils can range from high clay
content to very sandy consistency and may
include other materials, such as gravel or
pumice. With clay-rich soils, you could
consider building instead with adobe or
cob techniques. (See chapter 7 for more
about clay-based building methods.) If
you're determined to use earthbags, mix
more sand and gravel into the mix to break
up the clay, or tamp it well and ensure a
high stem wall to minimize its ability to
absorb moisture.
Water: This is added to the earth to facili-
tate the tamping, in order to achieve better
compaction. The moisture content of the
earth should be such that when a handful
is picked up and squeezed it holds its
shape, but you do not see or feel any liquid.
To prevent an excess of moisture, the earth
mixture can be soaked overnight.
Barbed wire: This is used between courses
instead of mortar to grip the bags. Four-
point wire provides a good grip; as a natu-
ral alternative, you can use branches of a
thorny plant or jagged rocks or stakes
pounded into the bags. Barbed wire can be
obtained on a coil or salvaged from an old
fence. If the bags you are using are 12
inches (300 millimeters) wide, only one
row of wire is needed. If the bags are 16
inches (400 millimeters) or wider, two
rows may be required.
Stabilizers: These are additives mixed with
the soil for increased strength, or to fortify
a finish coating. Typical stabilizers are lime
or cement. If constructed properly, an
earthbag structure should require no sta-
bilization. Cement can be used for bond-
beams and compression rings, for ex-
tremely strong structures that must carry
great loads, or for structures that are under
water. Be especially careful when using ce-
ment, which while ubiquitous in our soci-
ety, is associated with negative environ-
mental impacts. Cement-based finishes
should be avoided with an earthen build-
ing, because cement makes the walls more
impermeable, and earthen walls must
breathe over time. (The only exception is
on domed structures in very wet climates.)
Instead, the finishes can be earthen plas-
ters with a lime sealant or render. Other
options for finishes on earthbags are dis-
cussed in chapter 6.
TOOL S
The tools you will need to build with
earthbags are simple and easy to find or
make yourself.
Coffee can or shovel: Either may be used
for filling the bags or tubes. Cans are easy
to toss to people who are higher up on the
wall, but each person will find his or her
own favorite tool and technique.
Shovel for digging: A shovel with a cutting
edge will make it easier to excavate soil
from the site, to trench, or to collect fill.
BUILDING WITH EARTHBAGS
47
Tamper: This essential tool is used to tamp
or ram the bags flat once they have been
laid in place. Garden supply stores and
building centers sell manufactured tam-
pers. You can make a metal tamper out of a
piece of 1-3/16-inch (30 millimeter) diam-
eter metal pipe about 40 inches (1.5
meters) long welded to a 6-by-6-inch (150-
by-150-millimeter) square of metal plate
about inch (6 millimeters) thick. To
make an even lower-cost tamper, take a
plastic yogurt cup, fill it with concrete mix,
and place a stick studded with nails in the
center of the wet concrete, possibly with
rolled-up wire mesh for reinforcement.
Let the concrete cure for at least two weeks
before use.
A heavy block or chunky piece of wood
can also be used to flatten the sides of an
earthen wall or to beat the bags into any
shape desired.
A stand: A fold-out stand will aid in the
filling of small bags. (To ease the filling of
longer bags or tubes, prop a cut-off piece
of pipe in the opening.)
Water source, or buckets for hauling wa-
ter: If the soil is too dry, water may be
needed to help make an earthen mixture
more compactable. One of the reasons
that earthbag construction is very well-
suited to dry locales is that you can also fill
bags with dry sand, gravel, or sifted soil.
Water level: for leveling the ground.
Left: The tools for
4 6
Four-point barbed wire
on a roll.
Making a tamper.
Section of earthbag dome showing the compass in use.
Plumb line: A plumb bob and line allows
you to check a straight wall for vertical lev-
elness.
Wheelbarrow: This is used for transport-
ing material, for mixing cement or lime
into the earth to stabilize it, or for mixing
adobe or cob plaster.
Hoe: This may be more practical than a
shovel for mixing ingredients.
Blade or scissors: For cutting the bags or
tubes.
Wire cutters, level, ladder, tape measure,
gloves, and trowel: All of these will prove
useful on any building project.
Compass: Required only as a placement
guide for the bags in the building of sym-
metrical domes, a compass can be as simple
as a chain or a string, or more complex.
When the courses of the dome reach the
stage at which they must start to curve in-
wards (the spring line) the compass needs
to be extended after each row. This can be
worked out by making a drawing of the
dome, as in the drawing at left and page 44.
An extendable compass may be made
with a length of hollow pipe (electrical
conduit will work, or one of those tele-
scoping poles used for cleaning swimming
pools) attached at one end to a caster (such
as those on a grocery cart) from which the
BUI LDI NG WI TH EARTHBAGS
wheel has been removed. The caster will
allow for rotation as well as up and down
movement. The caster should be affixed to
a 4 x 4 (100 x 100 millimeter) post planted
upright in the ground at the center of the
dome. At the upper end of the pipe, use
pipe clamps to attach a guide made of an
L-shaped piece of metal.
P R E P A R I N G T H E F I L L
As I have explained, the bags are used as a
temporary formwork for the tamped or
rammed earth during construction of a
building and before the plaster is applied.
The plaster finish can be seen as a long-
term sheathing, which if maintained at-
tentively can be considered "permanent."
The material that goes into the bags can
therefore be of any consistency ranging
from very loosefor example gravel,
pumice, or sandto a more compactable
soil that contains varying amounts of clay.
The best fill for an earthbag wall is one
with the same consistency as the tradi-
tional mix for rammed earth: approxi-
mately 25 percent clay to 75 percent sand,
which will dry into a cementlike hard
block. However, earth seems to be suffi-
ciently compactable with as little as 5 per-
cent clay.
With soil that has a high proportion of
clay, it is probably better to consider an al-
ternative type of construction, such as cob,
adobe or one that makes use of other fiber/
clay composites; because the clay has bind-
ing properties, a bag to contain it is not
really necessary. However, bags are faster
to construct than cob.
If pure sand is used, you must take sev-
eral precautions. The sand must be made
slightly damp to facilitate the compaction.
The bags need to be wider to allow for
more stability, more buttressing needs to
be provided, and if domes are being con-
structed using the corbeling method, care
needs to be taken that each row does not
step in too fast. This type of dome can ac-
tually be much taller than masonry domes,
with steeper sides and larger buttresses,
such as on Shirley Tassencourt's dome (see
diagram, page 124). For increased stability,
it is also possible to tie down one course of
bags to the two below, creating a net with
wire mesh or strapping, or to construct the
dome over a permanent form such as
demonstrated in the Malawi project (see
page 142).
Whenever earthbags are used, but espe-
cially in flood areas, care needs to be taken
that the lower courses of the wall do not
contain clay, and are properly detailed to
shed water (see drawings on page 35). If
bags containing clay are exposed to water,
the clay can either expand and break apart
the wall or dissolve and seep out, leaving
cavities that create instability. The higher
courses need to be tamped or rammed well
to reduce the ability of any clay in the bags
to absorb moisture.
Generally, the earth excavated on site
can be used for fill. Be sure to remove top-
soil and set it aside for a future garden, in-
A construction compass, made with
telescoping pole and caster.
50
Two strands of barbed
wire placed between
bags during construc-
tion act as a mortar.
stead using the subsoil for construction.
Remove all large stones and organic mat-
ter from the earth mix, as these materials
too could create cavities later on. If a large
number of stones are found in the soil,
sift them out using appropriately sized
screens, and use them as gravel in the
lower courses of bags or for foundations,
as this nonabsorbent material will drain
well and prevent capillary rise of mois-
ture. If crushed pumice or scoria (a po-
rous volcanic stone) is used for earthbag
walls, it will serve as both thermal mass
and insulation (as in the Hart's house,
profiled in chapter 8), but smaller-sized
particles can wick moisture, so care
should be taken not to use too much fine
pumice or scoria in the lower courses,
which are prone to being damp unless a
damp-proof membrane is used, or unless
the pumice is mixed with cement. (For
discussion of pumice-crete, see chapter 3. )
If the earth used for filling is totally dry
when dug out, it needs to be sprayed with
water to ease compaction in the tamping
process. More compacted fill is ultimately
more stable. Remember, the soil should be
moist enough that when a handful is
picked up and squeezed it holds its shape,
but you do not see or feel any liquid, and
when a lump of the soil is dropped it falls
apart. The soil can also be soaked over-
night.
The appeal of the earthbag method is
that builders can use such a wide variety of
soil and other types of fill for construction,
only attending to these very general guide-
lines: not too much clay, not too many
large or sharp rocks, not too dry or too wet.
For information about doing soil tests
when building structures that require
more refined sensitivity to soil contents,
see chapter 7. For information about stabi-
lization, see chapter 6.
F I L L I N G B A G S O R T U B E S
Before beginning to fill the bags, make sure
the earth is moist enough to allow com-
paction. Bags may be filled in several ways:
with a shovel, tin can, bucket, or whatever
A team of three filling a long tube in Mexico.
BUI LDI NG WI TH EARTHBAGS
the person doing the work can lift. It is
never necessary to lift the bag itself: the bag
stays in place and earth is brought up to its
opening. Bags higher on the wall can be
filled in place. Cans of soil can be thrown
up to the person doing the actual filling
(see photo on page 53) . Bags filled by dif-
ferent people will vary in thickness, due to
differences in strength and technique. It is
therefore important that one person or
team builds a whole row to minimize the
changes in thickness during one course.
The rows may vary from each other, but as
long as each row is of a consistent thick-
ness, this is not a problem. Once a row is
complete, tamp it well, then place two
strands of four-point barbed wire on top
as keying for the next row. As you stack
bags in successive courses, remember to
always stagger the joints, just as in ma-
sonry construction.
Each tube or bag can be cut to the de-
sired length. How long do bags need to be?
If you are building a dome, it is good to
have one continuous length all the way
around, unless this would mean a length of
more than 30 feet, because beyond that,
the tube becomes difficult to fill.
For the foundation and the first few
rows of wall, it is good to use bags or tubes
that are as long as possible to minimize
breaks, for structural stability, but even
small bags that are well tamped can be
used for the foundations. When measur-
ing the required length, add an extra foot
of fabric at each end of the bag. You will
later fold over the surplus fabric to close
the bag.
A mechanical pump used for pumping
concrete can also be used to speed up the
process of filling the bags. For landscaping
or large industrial projects, where time
and labor are costly, professional builders
might use a continuous berm machine,
which extrudes a fabric-encapsulated con-
tinuous berm of sand, rock, or native soil
at a rate of 10 to 50 feet per minute.
Filling a Bag with More than Three People
Two teams can fill a long bag or tube from
the two ends using the following procedure:
1. Cut the tube to length (up to 30
feet).
2. Fold the edges of each opening back
as far as possible toward the middle,
as shown to the right.
3. When the folding reaches the mid-
point, start filling the tube from each
open end. As one person shovels in
the earth, the other can hold the end
of the tube open and unfold the ends
as it is being filled.
The speed of this method of filling bags
on the project in Mexico (see chapter 8)
averaged out to be 25 feet per hour, per
team.
Filling the bag from
both ends.
51
Filling the long bag
from one end.
Filling Bags or Tubes with Only One
to Three People
When working with fewer people, the bag
or tube should be filled from only one
open end. Once the desired length of bag is
cut, shovel or scoop as much material as
you can lift into the bag, then shake it
down to the opposite end. While one per-
son shakes the earth toward the end, a sec-
ond person can step on that end to prevent
the material from flying out.
Or, when working with smaller, more
portable bags with one end sealed, you can
shake the material down into the open
end, and lift the whole bag into position.
Once the bag is in place, fold under the
open end of the bag to close it. When a row
is complete, this bag should be tamped
solid and flat before the next course is
placed on top and is ready for barbed wire.
Another way to fill bags with a smaller
crew is to slide a cut piece of wide pipe in-
to the open end of a bag, like an ankle in a
sock. The pipe forms a chute for the earth
to go through. Each time a manageable
amount is shoveled in, take out the pipe
and shake down the bag. Be sure to avoid
letting the bag bunch up while it is being
filled; each load of earth must go all the
way to the end, with no gaps. A brick can
be placed under the bag to prevent creases
in the bag, or one of the crew can use a foot
to support the lower side of the bag as it is
filled. Use a piece of sheet metal or a board
to protect feet and clothing from the
barbed wire when working on top of a
course that has been keyed with wire.
Using Small Bags
If small bags are used, the wall will tend to
have a great many bag corners sticking out,
which makes plastering difficult, as much
more plaster is needed to cover these. To
prevent this, tuck in the bottom corners as
the bags are being filled. Utah earthbag
builders Kaki Hunter and Doni Kiffmeyer
named this process "diddling." When filled,
the open end of the bags can then be gently
lowered into place and those corners
diddled as well, tacked under the weighted
end of the full bag.
One person can fill small bags by using
a stand to keep the end open. Remember,
the small bags must be laid in a running
bond, with all joints staggered. The time
required to fill small bags for the Honey
House project (see chapter 8) averaged
four bags (approximately 6 feet or 2
meters) per hour, per person.
T A M P I N G
As noted above, to minimize unevenness,
each bag in a row should be filled to its
maximum capacity by the same team. To
create as level a wall as possible, do not
tamp until the whole row is filled. Once the
whole row is laid, it can be tamped until no
movement of the earth is felt. The sound of
the tamping, changes as the earth in the bag
is compacted, becoming less of a "thump"
and more of a solid "smack."
BUI LDI NG WI TH EARTHBAGS
53
Far left, top: Using the metal
tray to position the first bag
correctly.
Far left, bottom: Filling the
long tube using a plastic
pipe as the chute.
Left: Filling a bag using a
stand.
Below: Steve Kemble
tamping an earthbag wall
with a concrete tamper in
the Bahamas.
Inset: Untamped and
tamped sides of a wall.
52
"Diddling."
54
Points to Remember for
Earthbag Construction
Dampen the earth prior to filling the
bags to improve compacti on
In successive courses, stagger all joints
between bags, for stability
Have the same person or crew fill the
bags for a compl ete row or course, for
consistency
To minimize unevenness, do not tamp
until a whol e row is compl ete
In dome construction, tamp each row
flat, for stability
Place barbed wire or other key in
material between courses
Buttress all domes and straight walls
Buttressing wire. Each row of bags is tied to the
two rows below.
Tamping soils with high clay content lessens the earth mixture's
tendency to draw in moisture, but does not eliminate this ten-
dency entirely. Be sure to avoid having too high a proportion of
clay in the earthbags, especially in the foundation or lower courses,
which are more likely to be exposed to water.
You may also wish to tamp the sides of the wall, checking the
vertical straightness with a spirit level or plumb line. An advantage
of tamping the sides is that then the wall surface will require less
plaster. The disadvantage of a very level or even wall surface is that
the plaster has less surface area to key into.
K E Y I N G
After tamping, each course needs to be keyed with four-point
barbed wire or branches of a thorny plant, which will provide fric-
tion to prevent any shifting of the bags over time. If no barbed wire
is available, the bags can either be well buttressed, tied to the bags
below (see Kelly Hart's project in chapter 8), sandwiched between
wooden poles, or pinned with reinforcement rods. For very wide
and short stem walls or landscaping walls, barbed-wire keying is
not necessary. Also, on smaller structures, using rough rocks or
chunks of gravel between courses will provide adequate keying.
If the bags used are wider than 14 inches (350 millimeters), or a
dome is being constructed, two rows of keying maybe necessary.
This keying is especially important in corbeled domed structures,
providing tensile strength while enabling each row to step in
slightly.
S T R U C T U R A L R E I N F O R C E M E N T A N D B U T T R E S S I N G
In domes, there are two areas of maximum pressure that require
careful attention, especially in areas of high winds or seismic activ-
ity. The base of a dome can be buttressed on the outside with the
ground, with constructed benches, or reinforced with a "tension
ring." The other point of pressure is the top of the dome. If there is
any opening at the top, it must be reinforced with a "compression
ring."
A tension ring is a continuous and rigid ring at the base of the
BUI LDI NG WI TH EARTHBAGS
55
Reinforced tension ring. Bench acting as a buttress. Ground acting as a buttress.
dome, which absorbs the downward hori-
zontal forces that otherwise would cause
the base of the dome walls to splay out and
collapse. This ring has the same function
as buttressing and is needed in all struc-
tures in seismic zones and in domes that
do not have some form of buttressing
around the base. In most domes, unsta-
bilized material may be used in the bags
with which the walls are constructed, but
in seismic regions the ring around the base
must be stabilized with continous reinforce-
ment surrounded by concrete or cement-
stabilized rammed earth, metal, or some
other resilient material. Since this rein-
forced ring may be the most expensive el-
ement in an earthbag dome, it may be ad-
vantageous to consider buttressing the
structure in areas that do not have seismic
activity (see the diagram series above).
A compression ring is the tension ring's
counterpart at the top of the dome, neces-
sary if there is an opening there. It pre-
vents the dome from caving in because of
concrete bond
beam with
continuous
reinforcement
Earthbag dome with a compression ring and skylight.
skylight
bags filled
with earth
ties on to 3 or
4 rows below
56
BUI LDI NG WI TH EARTHBAGS
the upward, inward pressure of that open-
ing. Like a tension ring, a compression
ring needs to be continuous, made of con-
crete, metal, wood, or other material con-
taining sufficiently sized continuous rein-
forcement. For more complex structures,
consult an engineer.
While curved walls are structurally self-
supporting, straight walls need additional
support. The diagrams on this page show
If a wall is straight,
buttressing needs to
ways of reinforcing a straight wall with a
corner or with connected buttresses. Re-
member, for stability when constructing
intersecting walls and buttresses, always
stagger all joints.
O P E N I N G S
In an earthbag dome, the number of open-
ings cannot be too many or else the struc-
tural stability of the dome will be compro-
mised. The distance between openings
should be large enough to properly but-
tress the arch that forms each opening. In
general, openings that are square are best
suited for square houses; it is possible to
create small square openings in domes if
there is a lintel, but structurally this is not
a good idea.
During wall construction, where there
will be openings, leave loops of wire ex-
tending out from the strands of barbed
wire laid between the bags, which will
Corner of a buttressed house.
Staggered joints
at the corner of
the Three-Vault
House, Mexico.
Long bags"woven"
into place during
construction of the
author's retreat.
Buttressing during
construction at
Allegra's house,
Arizona.
If the wall is curved it does
not need buttressing.
A buttressed wall.
58
stabilized
bags
Several demonstrations of creating an opening
without the use of a wooden lintel.
Shirley's dome, showing different formwork on top
of the wall.
allow you to tie off these wires up and down around the opening
for added strength. Some builders reinforce their openings with
wire mesh, which can also be attached using these wire ends.
There are two categories of openings: arched, which do not need
wood, metal, or concrete as a lintel above, or square, which need
lintels, or which utilize a bond beam at the top of the wall as the
lintel.
Arched Openings
If the opening is in the shape of an arch, no lintel is necessary. One
way of leaving an opening in the earthbag wall is to use a form. A
form can be a circular object such as a wheel, a bucket, or a barrel,
or can be specially constructed out of timber in the exact space
desired. The opening can also be filled with earthbags that are sub-
sequently removed.
Several types of arches can be created, some of which are shown
in the drawings and photos. To make the "curved bag" window
shown above, stabilized earth must be used.
To make a form, cut an arch in the required shape out of ply-
wood or other flat material and duplicate it, then attach these flat
arches to each other with pieces of timber so that the ends are
parallel. Next, cover the whole arch with plywood or other flexible,
sheetlike material.
Make the form at least 2 inches (50 millimeters) wider on each
side than the intended size of the finished opening, to allow for the
thickness of the plaster.
When placing the form, make sure to position it on top of
wedges, as this will ease the removal of the form after the arch is
complete. These wedges could be chunks of timber or tapered log
ends.
Place a minimum of three well-tamped courses of bags above
the opening before removing the form.
When building a vault that connects to a structure through an
arched opening, the main opening should be located at the end
where the arched opening in the wall has no load-bearing function
(see page 2 6 ) . Some builders have constructed reforms for vaults,
BUI LDI NG WI TH EARTHBAGS
but this can be expensive because of the
quantities of materials required. It is less
expensive to make a permanent vault out
of bamboo or other bendable material,
which the earthbags can be layered
around, or a Nubian vault out of adobe
(see page 2 5- 2 6 ) . If you do decide that a
temporary vault form is necessary, it is
most economical to make one that can be
reused rather than demolished.
When the earthbag wall reaches the
height of the opening's bottom sill, place a
form where the opening will be, posi-
tioned on top of wedges to ease its removal
after completion of the arch.
As you stack the first three rows of bags
around the form, add additional perma-
nent buttressing on either side of the pri-
mary bags to contain the horizontal forces
that will act upon the finished arch.
The arch's "keystone" will consist of the
last three bags laid in position. These are
placed with their tops still open, then filled
up with additional earth from above, as
shown above right. The earth must be
shoveled into the last three bags simulta-
neously, to create the keystone effect. To
close these bags, either use nails (stuck like
tailor pins through the fabric of the bags),
or stitch them closed with a piece of wire.
59
Size and position of the form
used to make an arched
opening in a corbeled dome.
Construction of a form to create an arched window
opening.
Stitching keystone
bags after filling in
place.
wedge
wedge
line of
curvature
As emphasized above, before removing the form, you must
complete the rest of the wall with at least three tamped rows laid on
top of the arch.
Top: Window in the end of a vault, Mexico.
Middle: Stabilized arch, California.
Bottom: Arched forms.
Square Openings
Although square openings for windows and doors are not struc-
turally sound in dome construction, you can incorporate square
openings in a straight-walled earthbag building by providing
rough framing ahead of time or by cutting them out from the fin-
ished wall, provided the necessary buttressing is in place prior to
this excavating.
As shown on page 61, it is important to add sturdy diagonal
bracing to all window and door frames to keep them square during
construction. This bracing can be removed once the walls reach
full height. Door frames also need to be securely attached to the
foundation for stability.
The detailing around window and door openingsfor in-
stance, the seal between a windowsill and the earthbag wall be-
lowis extremely important in order to prevent penetration of
moisture. Also note that if a timber frame is used to provide the
structure for a building where earthbags serve as infill, it is impor-
tant to separate wooden members from the earthwall with a care-
fully attached waterproofing membrane to prevent moisture pen-
etrating through at seams between the earthbags and wooden
posts and beams or framed openings. (See chapter 6 for more in-
formation on waterproofing.)
B O N D B E A M S
Known in conventional construction as a "plate," a bond beam is a
rigid structural unit, usually made of wood, metal, or concrete,
that sits on top of a wall and evenly distributes the weight of a
subsequent floor or the roof. While not relevant to dome construc-
tion, bond beams are important in straight-walled construction to
tie together and stabilize the earthen structure at its point of great-
est outward pressure, especially in areas of high winds or earth-
quakes. In addition to serving as a level platform for a roof, a bond
BUI LDI NG WI TH EARTHBAGS
61
metal tray
lintel is
pinned to
earthbags
Elevation of doorway.
Section through doorway.
Below and bottom right: Window details. Always slope the external window
sill away from the building with an overhang of at least 2 inches (50 mm)
and a drip edge.
window
timber windowsill
with a drip edge
timber sill plate
metal lath
cement-stabilized
earthbag
damp-proof course
internal plaster
_ a n c h o r bolt to fix sill plate
to cement-stabilized
earthbag
Door frame securely fixed to stern wall
with diagonal bracing.
Window frame.
6o
62
beam can also serve the function of a lintel,
spanning the unsupported gap in a wall
created by a window or door.
In an earthbag building, depending on
its function, the bond beam can be made
of timber, steel-reinforced concrete, or
even cement-stabilized earth, well tamped
in the bags.
BUI LDI NG WI TH EARTHBAGS
63
Far left: A bond
beam in the
Bahamas.
Left: A formwork for
the bond beam,
which will be used
as a base for the
timber wall plate of
the next level.
Below: A conven-
tional greenhouse in
Colorado constructed
over a pumice-filled
bag stem wall.
Inset: Section through
the stem wall of the
greenhouse showing
the wall plate detail.
damp-proof course
row of well-tamped
cement- stabilized soil
papercrete (fibrous
cement) internal and
external plaster
well-tamped
gravel bags
5
T
he roof is one of the most impor-
tant factors keeping a building dry
and warm. A good roof protects
the inhabitants from rain, snow, wind, the
cold, and the heat. It will shed water away
from the house, directing it at the garden,
or will catch the rainfall to be stored for
later use. The roof can be a dominant fea-
ture, making a house stand out, or can help
a house disappear gracefully into the land-
scape.
The ideal roof for earthbag walls is one
constructed using the same materials as
the walls. The main attraction to most
people who discover this building tech-
nique is the possibility of using no wood,
Facing page: Cooling
tower of the three-
vault house at Cal-
Earth.
adobe plaster with shallow-root
plants and grass planted to prevent
it from being worn away by rain
(only recommended in rainy
areas; otherwise the
grass will dry out)
stabilized adobe
waterproof layer
two rows of
stabilized patties
A grass covering. In rainy climates a waterproof
membrane is necessary.
Covering for damp climates (see page 98). The outer
stabilized layer could also be made of papercrete.
Natural roofing
materials for earthbag
domes.
R O O F S
bamboo or willow
wrapped around
shingles of grass,
overlapping like tiles
65
66
Detail of a brick dome showing the bond beam.
Surface Finishes
Surface finishes for domed earthbag roofs,
to make them water-resistant though not
necessarily waterproof:
lime render or whi tewash
cement-stabiiized soil
papercrete
earthen plaster wi th lime render and
whi tewash
In wet climates a waterproof layer is
necessary underneath the plaster or
painted on top.
metal, or concrete, as well as the aesthetic value of an earthbag
structure. A dome, for instance, is quite an amazing space to be in
(some would say "nourishing for the soul") with an option of add-
ing at least one other floor while retaining its height and beauty.
Using a dome or vault is a roof-building technique that is finan-
cially and ecologically economical if no plentiful, renewable
source of wood is available. Concrete and steel contain high em-
bodied energy, as well as being expensive, and earth is a far
healthier option.
Yet, creating an earthbag dome might not be a solution to house
design in all climates, nor for every type of budget, culture, or in-
dividual. The amazing aspect of the earthbag technology is that it
is genuinely adaptable, allowing each individual to create a house
tailored to his or her needs. In many cases it is beneficial to com-
bine the earthbag wall system with a flat, pitched, vaulted, or other
roof system, depending on the requirements. For example, in areas
prone to high levels of rainfall throughout the year, it is a good idea
to combine the earthbag wall system with a more conventional
roof type that provides an overhang to protect the walls from the
constant rain.
B R I C K O R A D O B E R O O F S
An earthbag building can be covered with a shallow dome con-
structed out of masonry brick or adobe in areas where the climate
is relatively dry.
According to an old recipe I found on the straw bale listserve
(ht t p: / / sol st i ce. crest . org/ effi ci ency/ st rawbal e-l i st -archi ve/
index.html), a cheaper and more beautiful way of waterproofing
exposed bricks than covering them with cement or boards is to:
Stir 1 pound of finely powdered flowers of sulfur into 8
pounds of linseed oil. Bring the mixture to a heat of 2 7 8
degrees Fahrenheit, and then allow it to cool. Add some
drying oil and paint the bricks with the compound.
For more on waterproofing, see the discussion of finishes in chap-
ter 6.
ROOFS
V A U L T E D R O O F S
To my knowledge, a vault wider than 5 feet (1. 5 meters) has not yet
been successfully constructed using earthbags. Most vaulted roofs
are constructed from other materials and joined to the earthbag
walls using a bond beam.
If the soil contains some clay, one way of constructing a small
vault out of earthbags (approximately 3 feet [1 meter] in width,
which can serve as a connecting space between domes) is by stand-
ing the bags up and placing them in a leaning arch, as shown in the
top diagram.
Another better way of constructing narrow vaults is to create a
series of sturdy, self-supporting arches that, when joined together
and finished with plaster, create a continuous vault.
A narrow vertical leaning vault, as constructed for a passageway in the retreat.
carrizo, bamboo,
or hazel, or any
bundled reeds
that can be bent
into an arch
damp-proof
course
straw-clay mix for insulation
water-resistant layer
earthbags
concrete bond beam
straps
Detail of vault constructed in
Mexico out of carrizo.
timber bond
beam anchor
bolted to
cement-
stabilized
earthbag
below
6 7
Carrizo and earthen vault.
Ratio of Vault Wi dt h to Length
In vaults constructed out of earth (for
example, adobe), a safe ratio of wi dth to
length should be equal to no more than:
length = 1.5 meters x wi dth
wi th the wi dth not exceeding 12 feet (4
meters) overall.
For lancet vaults, the following ratio applies:
rise of vault = width/2 + 19.5 inches (50
centimeters)
A series of arches
creates a narrow vault.
damp-proof course
68
Types of trusses.
C O N V E N T I O N A L R O O F S
More conventional roof systems can also
be constructed on top of the earthbag
walls. The roofs are for areas with high
rainfall. It is always important for the roof
to have large overhangs (at least 18 inches
[45 centimeters]) on the sides, even the less
exposed ones. From the standpoint of en-
vironmental impact, it is better to create
roofs out of small sections of wood, if
wood is necessary at all, instead of timbers
from old-growth or slow-growing trees.
Wood can be obtained from fast-growing
trees in carefully managed forest planta-
tions, or builders can use wood-efficient
trusses, laminated timbers, or other engi-
neered wood-fiber products. Trusses can
be purchased prefabricated or can be built
on-site with local materials. A typical 2 x 4
truss provides a great deal of space for in-
sulation but does not provide extra living
space, unless the scissor truss is used (see
top diagram).
W A T E R - C A T C H M E N T R O O F S
Another supplementary purpose of a roof
can be to catch rainwater to be used for
washing, flushing toilets, watering the gar-
den, and even drinking after filtration. For
directing run-off to a water-storage reser-
voir, a good roof material is zinc-coated
metal, because ethylene propylene diene
monomer (EPDM)the synthetic rubber
commonly used for roofs, pond liners, and
water tanksis apparently slightly toxic.
The water can be collected into a cistern
located either inside the house or out in the
garden. If it is placed inside the house, care
needs to be taken of its location to avoid its
functioning inadvertently as a very large
heat sink, constantly drawing heat from
the house's living space. In a passive solar
building, the additional thermal mass of
the water in the tank can help store solar
gain. The water tank should be insulated,
which can be done with straw bales.
T H A T C H E D R O O F S
A long tradition in England, Ireland, and
Wales, thatched roofs are still in use today
on most cob buildings. Throughout
northern Europe, thatch was made of a
common reed grass (Phragmites) or tight
bundles of straw, usually wheat or rye.
Thatch conforms nicely to curved and ir-
regular roof shapes. The biggest advantage
of thatch, in addition to its aesthetic value,
is that the thatch itself is the waterproofing
layer and therefore does not require the
ROOFS
69
7 0
Straw-clay rolled onto
long straw, reed, or jute
spanning between
rafters. When straw-
clay rolls are used, no
board or mat is
required to support the
straw-clay mix.
addition of any artificial waterproofing
materials; moreover, thatch provides suffi-
cient insulation. A well-made thatch roof
can last a long time: straw thatch up to
forty years, and reed up to sixty. The main
disadvantage of thatch is that it is combus-
tible, but the fire danger can be substan-
tially reduced by incorporating measures
such as ceilings that reduce airflow to the
roof, a sprinkler system, or treatment of
the roof with flame retardant, as discussed
in Michael G. Smith's book The Cobber's
Companion or Michel Bergeron and Paul
Lacinski's book Serious Straw Bale (see the
bibliography).
L I V I N G R O O F S
A "living" roof is one that supports an
earthen mulch and plantings of grass,
mosses, or even a berry patch. This kind of
roof can be aesthetically pleasing, and can
make a house blend in to its surroundings.
The earth on the roof serves as extra pro-
tection for a waterproof membrane be-
neath, and in addition to helping the house
retain its coolness in the heat of the sum-
mer, the thickness of the roof covering is a
sound insulator. Such roofs have also been
known to protect houses from external
fires.
1. Rafter
2. Plaster finish.
3. Straw-clay.
4. Long grasses or reeds covered with straw-
clay and rolled up to create an insulating
layer.
5. Two layers of waterproof membrane.
6. Corrugated cardboard or carpet scraps for
cushioning to prevent puncture of the
waterproof membrane and to give the
roots a base to wrap around.
7. Soil.
8. Plants.
B. Detail showing the layers
of a living roof with plywood
1. Insulation between rafters covered with a
ceiling finish.
2. Plywood or other rigid board.
3. Timber batten (50 x 100 mm) to stop the soil
from sliding off an angled roof.
4. Corrugated cardboard or carpet scraps.
5. Two layers of waterproof membrane.
6. Corrugated cardboard or carpet scraps for cush-
ioning to prevent puncture of the waterproof
membrane and to give the roots a base to wrap
around.
7. Soil.
8. Plants.
C. Detail showing
layers of a living roof
with straw-clay option
1. Rafter.
2. Carrizo decking.
3. Straw-clay for insulation.
4. Two layers of waterproof membrane.
5. Corrugated cardboard or carpet scraps.
6. Soil.
7. Plants.
ROOFS
This type of roof needs enough rainfall to ensure the watering
of the vegetation, or the roof can be planted with local plants that
do not require watering. Ideally, the roof's pitch should not exceed
35 degrees, or the mulch and plants may slide off, especially when
wet or weighed down with snow (it is possible to construct a sys-
tem of shelves and netting to prevent soil slippage).
The layers of a typical living roof are as follows, starting from
the lowest layer which sits on the roof rafters:
1. A layer that creates a smooth surface. This can be anything
from plywood sheathing or boards to a smooth insulative
straw-clay finish on top of rough surface decking such as
carrizo (see figure c left) or previous straw-clay layers
(figure a). If plywood or boards are used, and the roof has a
steeper pitch, it is advisable to create a textured surface to
prevent subsequent layers from sliding off (figure b).
Nailing on some 2 x 4 boards, or shaping the straw-clay to
create horizontal undulations, will help (figures b and c).
2. A waterproof membrane such as bentonite clay with a layer
of geotextile membrane to prevent root penetration, or
polymer-based modified bitumen, or some other kind of
durable, reinforced, and impermeable sheeting.
3. A cushioning layer of corrugated cardboard or carpet scraps
placed on top of the waterproof membrane to prevent it
from being punctured and to give the vegetation something
to take root in.
4. A layer of soil or other organic matter 2 to 8 inches (50 to
200 millimeters) deep, seeded with plants. Rock gardens are
of course more appropriate in drier climates.
L O W - C O S T F L A T R O O F S
Roofing is one of the biggest challenges in low-cost construction,
since it is usually the most expensive part of the structure. When I
worked in Mexico on a housing project organized by the Canelo
Project, the roof systems developed were for straw bale houses
that cost between 350 and 500 U.S. dollars. The roof types we used
Roof trusses coming together in a vortex.
Roof construction consisting of carrizo decking with
straw-clay for insulation used on houses in Xochitl,
Sonora, Mexico.
Cardboard box roof construction used on the houses
in Aves del Castillo, Sonora, Mexico.
A. Detail of living roof
showing straw-clay"rolls"
for insulation.
71
Roof construction using cardboard boxes filled with straw on a concrete-
reinforced grid supported by chicken wire.
reinforced concrete beams
forming a lattice around the
boxes
powdered
marble, white
cement and
acrylic
waterproofing as
the roof finish
chicken wire
Roof construction consisting of carrizo decking with straw-clay for insulation and
sculpted parapets.
Precast concrete vigueta roof system with carrizo and straw-clay insulation.
Viguetas are short structural supports that span between main beams. Instead of
concrete viguetas, short timber poles could be used.
there are also well suited for low-cost
earthbag construction.
For the rafters we used 3- to 4-inch- (7 5
to 100-millimeter) diameter poles, dis-
carded from timber cutting operations
because they were too small for convenient
milling. The roof surface or decking was
constructed of carrizo and covered with
two layers of straw-clay mix. The first layer
of the mix contained uncut straw to sculpt
the parapets and build necessary thickness
(6 to 7 inches) to provide reasonable insu-
lation value. The second layer contained
finely chopped straw and clay to even out
the surface and prevent puddles. The roof
finish was a mix of powdered marble,
white cement, and an acrylic waterproof-
ing compound as a final coating (see the
discussion of waterproof finishes in chap-
ter 6).
Another low-cost alternative option for
a dry climate (used by the Canelo Project
in Mexico) is a roof made out of cardboard
boxes filled with straw or other insulating
material, which are laid flat on some form
of inexpensive joist or rafter arrangement,
or chickenwire for support, as shown at
left.
R O O F I N S U L A T I O N
Many materials can be used to insulate a
roof, the lower-cost options being straw-
clay (a thick clay slurry mixed with a lot of
straw, as shown in figures a and c on page
7 0) or straw bales, as described below. A
slightly more expensive option would be
ROOFS
insulation blown in between rafters, which
could be recycled cellulose, hemp, wool, or
coconut fiber. As for insulating a flat roof,
if pumice is locally available it can be used
by placing 8 to 12 inches (200 to 300 milli-
meters) or more of small pumice (only
small particles of pumice wick moisture)
with 6 inches of earth on top to allow for
planting. An insulated roof has to be
framed in at the edges like a box to contain
the large volume of materials.
Another type of insulated living flat
roof uses straw bales as insulation. The
slope should not exceed 30 degrees. As in
the other living roofs discussed, a water-
73
proof membrane is placed between the
decking and the straw. Then straw bales
are laid flat, leaving a gap of 3 to 4 feet (1
meter) at the edges where flakes of straw
can be used to taper the roof to the height
of its frame. When the bales have been laid,
cut all the strings to loosen the straw. For
the first winter and spring, leave this ex-
posed to allow the straw to soak up the
moisture, then cover it with a very thin
layer of aged compost and sow flower
seeds. The best plants for such roofs have a
shallow root network and retain moisture
well, for instance strawberries. Imagine
having a roof full of strawberries!
Natural Finish for Flat Roofs
A durable finish for flat straw-clay roof surfaces can be made wi th a cappi ng of t wo coats of
-inch (12 millimeter) lime render (1 part lime to 3 parts sand).
Here are t wo recipes for waterproof finishes to be painted on the surface:
1. Dissolve 2 ounces (70 grams) of alum (aluminum potassium sulphate) and 2 ounces (70
grams) of salt in 2 cups (Viz liter) of water. Add this mixture to 5-1/3 quarts (5 liters) of water and
mix in 1/16 sack of lime. Use this to paint over the finished lime-plastered roof surface.
2. Apply five coats of dissolved alum and soap, alternating these in the following way:
Day 1: Dissolve 14 ounces (400 grams) of soap in 4 cups (1 liter) of hot water and brush on
roof surface.
Day 2: Dissolve 14 ounces (400 grams) of alum in 4 cups (1 liter) of hot water and brush on
roof surface.
Alternate these for five days, and reapply every year or two.
Recipes make enough finish for approximately 30 square meters.
7 2
layers of carrizo forming
the roof decking
75-100 mm (3'-4') vegas
earthbag wall
straw-clay
powdered marble, white cement
and acrylic waterproofing as the
roof finish
straw-clay
carrizo
precast concrete
"vigueta"
powdered marble, white cement
and acrylic waterproofing as the
roof finish
cardboard
box filled
with straw
6
A
s with any building, keeping the
water out of an earthen house is
one of the greatest concerns of
builders. As the cob builder's proverb of
Devon, England, says: "Good shoes, good
hat, and a coat that breathes." This is what
an earthen house needs to survive for
many decades.
Good shoes, to raise the building suffi-
ciently off the grounda sturdy, well-
drained foundation.
Good hat, a generous overhang to pro-
tect the walls from erosion from the rain.
A coat that breathes, a plaster that allows
the passage of moisture.
This chapter applies to internal and ex-
ternal earthen plasters (often called "ren-
ders," when exterior) for earthbag domes
and other types of earthbag houses, as well
as compatible finishes for benches, ovens,
stoves, or any other earthen structures.
In the earthbag construction system,
the wall surface is never the bare earth, but
whatever material the bags are made out
of. Rendering an earthbag house is neces-
sary for several reasons.
If the bags used for the construction are
polypropylene, they need to be covered
within the first two months of exposure to
ultraviolet light (direct sunlight), as UV
light makes the bags deteriorate, exposing
the material inside the bag. If the material
inside the bag has 10 percent or higher clay
content and the structure was properly
tamped or rammed throughout the con-
struction process, the walls should remain
solid and stable even when the bags have
deteriorated. However, if the fill is of a
loose composition, such as silt, sand, grav-
el, or pumice, the bags must be covered.
The type of covering used will depend
mainly on the climate and on the design of
the house. For example, a dome in a rainy
climate will require a plaster that is water
resistant, such as lime, papercrete, or ce-
ment-stabilized soil. In extremely wet cli-
mates a waterproofing layer on the top
part of a dome or vault is essential (see the
chart on page 7 7 ). If the water-resistent
render becomes saturated with water and
has no form of sealant or impermeable
membrane, the moisture will go down with
gravity through the earthbags. If the inte-
rior is covered with an earthen plaster, this
will quickly absorb water and come apart.
On the other hand, if the house is designed
Facing page:The Hart's
dome covered with
papercrete render.
75
WE A T HE R P R OOF I N G A N D FI NI SHES
with a conventional roof and wide over-
hang, and is raised up from the ground by
the foundation and stem wall. The walls do
not need a water-resistant render, being
protected from the driving rain, and an
earthern render can be used externally.
If the bags used are made out of burlap
(hessian), they will also need to be covered,
but they have a longer exposure life than
polypropylene.
Another reason for rendering the exte-
rior of a wall constructed out of earthbags
is that the surface has many grooves and
seams that in some extreme weather con-
ditions can be penetrated by rain, which
must be prevented of course. The grooves
can be extremely useful when applying a
render, however, providing a "key-in" area
for both external and internal plasters. If
for aesthetic reasons the ribbed pattern on
the wall is desired, a render can be sprayed
on, retaining the pattern of the bags.
E A R T H E N P L A S T E R S
If any plaster is used on a bare earthen wall
that contains clay, the plaster should be a
coating that breathes, allowing any mois-
ture that enters the wall to escape. Earthen
plasters have been used extensively in
many countries for many centuries. As
well as being used as a finish coat for
adobe, cob, or straw bale they also make an
excellent covering for earthbag walls that
have a roof overhang. With earthen plas-
ters, whatever moisture does penetrate
into the walls will be absorbed automati-
cally by the clay, due to its hygroscopic
(water-thirsty) properties, and then re-
leased to the outside. There may be no
other building material capable of regulat-
ing moisture levels as effectively as clay,
which continually absorbs and releases
moisture in response to the humidity of
the home. With thick and solid rammed
earth, adobe, or cob, an external render
may not be necessary.
In Devon, traditional cob houses have
survived for centuries without any plaster
coating (they say it takes one hundred
years to wear away one inch of cob). Pro-
vided that cob walls are protected from
actual erosion caused by the abrasion of
driving rain, there is no necessity for exter-
nal render, because moisture will evapo-
rate very quickly from an exposed cob sur-
face. With earthbag construction, how-
ever, rendering the external surface is a
necessity, as emphasized above.
Among the advantages of earthen fin-
ishes are these attributes:
moisture-control
fire-resistance
odor-absorbent
nontoxic
when dry, are unaffected by frost
aesthetically pleasing
Earthen walls covered with earthen
plaster may give the impression of having
grown out of the landscape. Their subtle
colors, complementing those of the
ground that surrounds them, can add
greatly to the charm of the countryside.
WEATHERPROOFI NG AND F I NI S HES
77
Meanwhile, among the disadvantages
of earthen plasters are that they have a low
structural resilience, therefore the design
of the house is critical. If they are made
with earth that possesses a high clay con-
tent, or with very fine sand or silt as the
filler and little or no straw, the plaster may
be easily eroded. Also, earthen plasters are
affected by frost in cold climates; if mois-
ture is allowed to penetrate the surface, it
will expand and contract as it freezes and
thaws, breaking up the plaster. In cold ar-
eas it is a good idea to cap the earthen plas-
ter with a lime plaster.
In locations where the plaster finish is
steadily eroded by weathering, it has to be
maintained on an annual basis. This can
be turned into a fun ritual.
A P P L I C A T I O N
Earthen plasters are incredibly flexible to
work with, allowing everyone to find a
personal way of mixing and plastering.
They can be applied in two or more stages.
The purpose of the first layer is to fill in
large gaps and crevices and to build up the
main bulk, creating a fairly even surface
for the smoother plaster to go on. This
first layer contains straw that is either un-
cut; direct from the bale, which provides
an interwoven stability; or finely chopped,
which is easier to mix in larger quantities
and is also great for building up thickness.
Long straw in the mix creates a plaster-
reinforcing network and helps to fill out
large holes or build up bulk where it is
needed, as in sculpting the sills around
windows.
An earthbag wall contains indentations
between the courses of tamped bags, mak-
ing it easier for the plaster to "key into,"
or adhere. No plaster-reinforcing lath is
necessary, as this can interfere with the
earthen plaster being keyed into the wall.
A good plaster mix is already well rein-
forced by straw. As this first coat of plaster
Finishes for earthbag
domes and walls.
For earthbag
houses wi th
conventional
roofs providing
appropriate
overhangs, no
waterproof layer
is needed.
7 6
is applied, it should not be smoothed out
too much, but instead left rough, or into
finger-sized holes so that the next layer of
earthen or lime plaster will adhere. If the
plaster does not stick to the wall, pound
wooden pegs into the grooves between
courses; these can also be inserted during
construction.
The second coat of earthen plaster is
more refined and can be very thin, just
enough to allow a final smoothing out.
This can be a mixture of finely sieved sand
and clay and, if desired, finely chopped
straw, along with wheat flour paste or an-
other stabilizer.
S T A B I L I Z A T I O N A N D
A L T E R N A T I V E S
Stabilizers are generally used to make ren-
ders or plasters more durable and resistant
to moisture. They are the "glue" that can be
used to bind filler particles such as sand,
earth, gravel, or fibers such as straw. Stabi-
lizers can be used as additives to earthen
plasters if the earth mix does not contain
enough clay to provide the binding force
and moisture resistance required.
Stabilizing earth is a very complex pro-
cess, since not all stabilizers are effective
with all soil types, and there are many fac-
tors that influence compatibility, includ-
ing clay content, soil particle size and type,
pH balance, and climate. Other factors
that must be taken into consideration are
the type of application and the reliability
of periodic maintenance, as well as aes-
thetics and cost.
As explained below, if an earthen plas-
ter is well mixed and contains a good dis-
tribution of clay, aggregate, and straw,
adding stabilizers can be largely avoided
through design features. But earthen walls
and plasters must be stabilized if the
earthen mix does not produce enough
binding strength (that is, does not contain
enough clay). Yet remember, houses built
out of earth need to move slightly over
time, and they are especially sensitive to
dampness and temperature, so they need
to breathe, releasing moisture. Modern
stabilizers and sealants result in severe
damage to earthen buildings, because they
tend to restrict movement and permeabil-
ity to moisture. Lime-based or other natu-
ral stabilizers do allow the walls to breathe
and move, adhere much better to earthen
walls (not requiring chicken wire or stucco
netting), and produce more porous fin-
ishes than Portland cement, the most
widely used industrial stabilizer, which is
an expensive and environmentally contro-
versial material, as discussed below.
It is possible to improve the characteris-
tics of many types of soil (especially sandy
soils) by adding stabilizers. These stabiliz-
ers can be used in the earthwalls them-
selves or in their skin as a surface protec-
tion. Due to the vast variety of soil types,
stabilization is not an exact science, and
research is continuous. According to CRA-
Terre's Earth Construction, "The best
known and the most practical stabilization
methods are increasing the density of the
soil by compaction, reinforcing the soil
WEATHERPROOFI NG AND F I NI S HES
be reused (see the diagram on page 8 1
showing the lime life cycle).
In industrialized societies, an increas-
ing number of people have been affected
by "sick building syndrome," which is a
form of poisoning harming people who
live and work in buildings with insuffi-
cient ventilation in which toxic vapors are
given off by artificial, chemical-intensive
building materials and paint. Cementi-
tious finishes release carbon dioxide, a
greenhouse gas, as they cure. Over the
longer term, they seal in moisture and
therefore can cause air-quality problems
and propagation of mold.
Cement is also a more expensive mate-
rial, because it contains higher levels of
embodied energy, although unfortunately
in some countries where demand for lime
is very low (as in the United States), the
healthier option can be as expensive as ce-
ment. The benefit of lime is its superior
quality, and when properly applied it is
worth every additional effort and expense.
Sources of stabilization include:
vegetable stabilizers
processed natural binders
animal stabilizers
mineral stabilizers
If a house is built in rainy or damp cli-
mates, the walls could be prone to severe
weathering from driving rain and frost.
With effective planning and the right de-
tailing, originating all the way back in the
initial design and building process, it may
with fibers, or adding lime, bitumen, or
cement." (Houben & Guilland 1 9 9 4) When
choosing the best stabilizer for a particular
soil, many factors such as the clay content,
acidity, and texture must be taken into ac-
count, and many samples- must be made
prior to construction. Again from
CRATerre, "It is particularly unfortunate
that many practitioners of systematic sta-
bilization do not know, or do not appreci-
ate the original characteristics of a soil, and
start about stabilizing soil with undue
haste, when it is not particularly useful."
The wrong stabilization may do more
harm than good.
As a case in point, cement can be a real
enemy of earth architecture, apart from
the few selected applications such as bond
beams on top of walls, compression rings
in domes, and stabilization of sandy soil
when making soil cement, which can be
applied as a render to earthbag domes in
areas with high rainfall. But cement should
never be applied on top of an earthen plas-
ter, as this will eventually crack and peel
off. As a general rule in earth architecture,
never place a hard, modern, nonbreathing
material on top of a more flexible surface,
as this will never form a solid bond and will
eventually separate, as well as create con-
densation and other moisture problems.
Buildings constructed of local stone,
earth, and lime cause far less environmen-
tal damage than concrete and steel. Earth
and stone are reusable, and old, dry lime
render is chemically limestone again, just
as when it was first quarried and can also
7 8 79
be possible to forgo the use of stabilizers
and instead use a plaster made of just
earth.
There are several ways to protect
earthen walls without using lime or Port-
land cement for stabilization. During the
design and detailing process, familiarize
yourself with the direction of the sun and
driving rain, and plan accordingly to pro-
vide a roof with a large overhang (a mini-
mum of 18 inches or 450 millimeters on the
least problematic side). Extra-large porches
can be integrated into the house layout on
the sides that are most vulnerable from
wind-driven rain. The more protected the
walls are, the less protection that plaster
needs to provide. Remember, each wall can
be slightly different; the most exposed wall
can be the only one capped with lime plas-
ter. Always slope surfaces away from the
ground around the base of the house as
well as sculpted windowsills, alcoves, or
seating to shed the water. Design these to
extend out at least 2 inches (50 mm) from
the wall, with a drip edge (see the diagrams
on page 61 ) . Temporary screens could be
installed as necessary to stop the seasonal
rain, or to prevent melting snow from
eroding the walls, for example a bamboo
or willow screen. Or if bad weather is year-
round, on the side where the most snow
settles or the strongest winds blow, a high
stone wall could be incorporated into the
base of the walls. Permanent screens could
also be built to keep driving rain off the
wall, keeping a distance of a couple of
inches away from the wall to allow for ven-
tilation.
Adobe walls are traditionally protected
by earthen plasters that are annually
"topped up," but allow the wall to breathe.
This can also be applied to earthbag as well
as straw bale houses. Other ways of mini-
mizing the penetration of moisture in-
clude sealing the earthen plaster with oil or
whitewash (see list of sealants starting on
page 9 2 ) ; stabilizing the earthen plaster
with lime, wheat-flour paste, or other
plant, animal, or mineral stabilizers (see
the list starting on page 8 1) ; or putting a
final cap of limea more durable, but still
breathing surface, over the earthen plaster.
Prior to any construction, it is crucial to
know your soil. See chapter 7 for a discus-
sion of soil-testing methods.
Stabilization is not compulsory. If the
soil contains enough clay, you can ignore
Caution!
Stabilizers function as binders in the
mixture but are not sufficient on their own.
To make them solid and hard, they need to
be combi ned wi th other fillers, for example
nonexpansive particles of soil such as sand,
silt, gravel, or fibers.
Never layer a rigid, modern, non-
breathing material on top of a softer,
breathing surface. The layers will eventually
separate.
WEATHERPROOFI NG AND FI NI SHES 8 1
the whole question quite satisfactorily. As the CRATerre publica-
tion Earth Construction explains,
there is clearly a tendency at present to the over systematic
use of stabilization, which is regarded as a universal panacea
for all problems. This attitude is unfortunate, as stabilization
can involve considerable extra costs, ranging from 30 to 50
percent of the final cost of the material. Furthermore,
stabilization complicates the production of the material. It is
thus advisable to insist that stabilization is only used when
absolutely essential and that it should be avoided where
economic resources are limited.
Vegetable Stabilizers
The following vegetable-based materials will serve as effective sta-
bilizers for earthen plasters:
oilscoconut, linseed, and cotton, which need to be in
"boiled" form to speed up the drying process
juice of banana leaves, precipitated with lime, improves
erosion resistance and slows water absorption
prickly pear juice (found in the southwestern United
States)
wheat flour paste, or any starchy material
Linseed oil can either be brushed on the finished surface of an
earth plaster, as is often done with the final layers of earthen floors
(see chapter 7 ) or can be mixed into the final batch of plaster itself.
To make prickly pear juice, the cactus has to be boiled until very
soft, then its juices squeezed out. The resulting soupy liquid is then
combined with the clay and soil mix that is to be used for the plas-
ter finish. Like any other stabilizer, this has to be tested prior to use,
as it reacts differently with different soils.
Wheat flour paste is an inexpensive stabilizer for earthen plas-
ters that is used by natural builders throughout the United States.
Harvesting prickly pear cactus.
Prickly pear cactus being boiled.
8o
I learned it from Carol Crews of Gourmet
Adobe, while we were making clay paints,
and it can be applied like a paint to earthen
plasters or floors. It can be made using
commonly available flour, as described on
page 9 6.
To make a plaster without using lime or
clay as the binder, you can combine sand
with manure and wheat flour in the fol-
lowing proportions:
4 parts flour paste (see page 9 6)
3 parts sand
2 parts manure
Other processed natural binders that
can be used to stabilize earthen plasters
when too little clay is present include
wallaba resin; rosin from oily pine resins,
obtained during distillation of turpentine;
copal, made from tropical tree resins,
added in a proportion of 3 to 8 percent for
sandy soils; gum arabic, from the acacia
tree; and molasses.
Animal Products as Stabilizers
Among the most popular animal stabilizers
in use today are the following: eggs, blood,
and casein (dried milk) as proteins; urine
and manure, as uric acid; casein (dried
milk); and glue made from animal parts or
byproducts. Termites secrete a chemically
active substance, and termite hills stand
up well to rain. Their soil can be mixed
with other soils for the production of
blocks that adhere effectively; perhaps this
soil would also stabilize earthen plasters.
To make casein glue to stabilize earthen
plasters, soak about 1 ounce (25 grams) of
casein powder and ounce (8 grams) of
borax in enough water to form a putty (to
make casein, see page 9 8 ). The putty can
then be diluted with water to a consistency
suitable for mixing with the soil ingredi-
ents of the plaster. For more casein recipes
see the end of this chapter.
Mineral Stabilizers: Lime
For thousands of years in Europe, lime has
been used as a mortar for stone or brick
construction; as an exterior or interior
plaster, when mixed with sand; and when
mixed with water, as a white paint com-
monly known as whitewash. In the mi d-
nineteenth century, cement and gypsum
unfortunately became more common
building materials. Lime was slower to
build with, and required artisinal skills
and good climatic conditions during ap-
plication, but produced durable and at-
tractive results. Lime plasters and finishes
harmonized with seasonal changes in hu-
midity and temperature, like clay prevent-
ing an overly dry or wet atmosphere by
evaporating away excess moisture or ab-
sorbing it as necessary, fostering a healthy
living environment. Simultaneously, due
to its alkalinity, lime does not allow the
growth of mold on the walls, therefore cre-
ating healthier conditions in wet climates.
Using lime as the binder in renders,
plasters, and mortars works best when
sand is the filler. Lime is not the most effec-
tive stabilizer to use with an earthen plas-
WEATHERPROOFI NG AND FI NI SHES
An earthen house with partial lime render, Peru.
ter or adobe mix that contains clay, be-
cause the lime and clay seem to "compete"
as binders. Ideally the mixture should turn
into a creamy paste, which will result when
it is dry in a finish that is more wear- and
water-resistant than clay alone, but in real-
ity this is rarely achieved due to variations
in the pH of clays. Therefore combining
clay and lime can make a crumbly mix, and
when used for stabilizing a wall material
such as adobe, can reduce its compressive
strength.
The theory is that, since lime is alkaline,
it combines best with acidic soils. The
higher the pH of the soil, the more lime is
needed to stabilize it. Lime apparently
does not react well with alkaline soils,
therefore carrying out tests is crucial to
finding out the soil's behavior. If the mix
of earthen plaster and lime does not turn
smooth and creamy, the addition of either
a more acidic ingredient such as manure
or organic soil may help. But care needs to
be taken; always test the mixes by making
samples before beginning to plaster an en-
tire wall.
L I M E P L A S T E R S
Historically most buildings in the United
Kingdom used lime for interior plasters
and exterior renders. Cob buildings, if
rendered at all, were traditionally covered
with a lime-based render applied directly
to the cob. This render consisted of lime,
which serves as the binder, and sands and/
or aggregates, which provide bulk at low
cost, and which control shrinkage. It is
best to use aggregate that has a good range
of particle sizes.
Fiberfor instance, hairwas often
added to the traditional mix to minimize
the shrinkage cracks that often occurred.
Cow hair was preferred, but was harder to
obtain, so goat hair was frequently used.
Some straw bale houses that are being ren-
dered in lime use straw as the fibers.
Using lime plasters has several advan-
tages. When lime used in buildings has set,
it turns back to limestone, which is chemi-
cally the same as the lime that is quarried,
reacts with
carbon dioxide
CO2
H2O
when drying
water
limestone
heat causes carbon
dioxide to escape
evaporates
lime putty
The life cycle of lime.
After Lime in Building
by Jane Schofield (Fig.
108, p. 123)
82 83
quicklime
H2O
water is added
84
Slaking lime in Xochitl, Mexico.
therefore it can be reused if the building is
destroyed and does not involve any pro-
cessing that will harm the environment.
In terms of healthy-home consider-
ations, lime plasters and washes usually
prevent condensation and an overly dry
atmosphere, because the moisture is ab-
sorbed and then given out, contributing to
higher air quality. Also, due to its alkaline
properties, lime prevents mold problems.
Lime is ideal for use both as an exterior
render or as an interior plaster or wash.
The chemical process of obtaining lime
involves heating calcium carbonate
(CaCO3 from limestone or shells to 1, 200
Celsius. This can be done in kilns (shells
can also be heated in a pile covered with
cowpats and coconut husks). The heating
causes carbon dioxide (CO2) and steam
(H2 O) to escape, and quicklime, or cal-
cium oxide (CaO), remains. At this stage,
Caution!
Always add the
quicklime to
water, never add
water to quick-
lime, as this can
cause an
explosion!
since the water has been driven off, it be-
comes very "thirsty" and reacts dramati-
cally with water (even water in the air, or in
the skin or eyes).
When the quicklime is soaked in water,
it turns to slaked lime, due to hydration.
This process produces a lot of heat, as the
mixture boils violently. This is known as
slaking. The resulting slurry is calcium
hydroxide (Ca(OH)2 ), known as lime
putty.
When applied on a wall surface and
therefore exposed to air, the lime reacts
with the carbon dioxide in the air to form
limestone again, that is, calcium carbon-
ate, (CaCO3). This happens as it dries on
the building. The water evaporates, and
the lime hardens through carbonization,
thus completing the cycle (Schofield 1 9 9 4) .
Making Lime Putty (Slaking)
For this task it is necessary to wear protec-
tive clothing, including gloves, goggles,
and mask. Since quicklime is caustic, it can
burn your skin, and during the slaking
process the mixture can spit violently
while boiling.
It is recommended to use 2 parts water
to 1 part quicklime.
Slaking has to be done outdoors with a
metal container, making sure it is not
placed on any flammable material, be-
cause the container will get extremely hot.
The water is poured in, then quicklime is
added slowly to the water, with one person
stirring at all times (a backhoe is the best
WEATHERPROOFI NG AND F I NI S HES
85
tool for large quantities). As more quick-
lime is added, the mixture starts to boil
and bubble. When that happens, stop add-
ing quicklime and keep stirring until the
mixture ceases bubbling, or else the lime
will burn and be of lower quality. The bet-
ter the quicklime mix, the faster the hydra-
tion process occurs. The mixture should
be stirred continuously until all the lumps
are broken down, and until the mixture
has cooled down and is of a creamy consis-
tency. It can then be sieved through a 7 1 6-
inch (2 mm) sieve to take out the un-
burned limestone pieces.
The resulting mixture is lime putty.
When left standing, the lime sinks and the
water sits on top. For best results it is rec-
ommended to leave it to mature for at
least three months prior to any use to en-
sure that all the calcium oxide has hy-
drated, and the longer it sits the better it
will be, though in Mexico we used it after
only one month. While curing it must re-
main in a sealed container to prevent it
from drying out, which is the carboniza-
tion process whereby the lime putty will
turn back to limestone, losing its binding
properties and therefore becoming useless
as a plaster.
Lime putty made from quicklime is by
far a superior material to the bagged hy-
drated lime available from garden supply
stores, which when soaked in water pro-
duces a putty that is generally not as good.
The problem with the bagged material is
that it might have been sitting in the shop
for a long time, which means many of the
particles in the mix will have already re-
acted with moisture in the air and carbon
dioxide to form limestone, making them
inactive and therefore weakening the mix.
To make lime putty out of bagged hy-
drated lime, mix the lime with water in a
bucket to form a paste, cover this mixture
with more water, and put an airtight lid on
the storage container. Store for several
weeks before using. Make sure it does not
dry out by adding water to it occasionally.
The longer it sits the better it gets. If this
bagged lime is not very fresh or of the best
quality, mix 1 part of the resulting putty
with 2 parts sand (instead of the 3 parts
suggested below) to compensate for the
inactive particles. To further strengthen
bagged hydrated lime, add some of the
more expensive "hydraulic" lime, which
sets faster and is more frost resistant after
Earth houses with lime render on a street in Cuzco, Peru.
just three days instead of two weeks. A
good compromise is 1/3 hydraulic lime to 2/3
hydrated lime.
Making Lime Plaster or Render
In order for a lime plaster to dry and be-
come limestone again, it needs to give off
all its moisture and draw in carbon diox-
ide; therefore, it cannot be applied in thick
layers. When applying a first coat of lime to
an earthbag surface, much crushed aggre-
gate or straw needs to be added to allow for
drying in the deepest areas keyed in be-
tween the bags. It is therefore better to first
cover an earthbag wall or dome with
earthen plaster to fill in those deepest
voids before applying subsequent coats.
Lime plasters can vary enormously, de-
pending on the type of lime, aggregate,
and particular use. The proportions of
lime to sand may vary between 1: 2 for a
smooth, fine finish to 1:5 for a rough first
coat. For greater strength in a plaster, the
sand particles used should be well graded,
ranging from very fine to coarse in one
mix.
As mentioned earlier, the only differ-
ence between the mix for interiors and ex-
teriors is the size of the sand or other ag-
gregate. A finer mix is best for the inside,
and a coarser for the outsidefrom very
fine dust to as large as 3/16 inch (5 millime-
ters) for interior plaster, and up to twice as
large for exterior renders, which should be
angular in texture to reduce the penetra-
tion of moisture. Limestone aggregate is
particularly recommended, because then
the filler binds especially well. If sea-
dredged sands are used, they require wash-
ing several times in clean water to remove
salts.
The most popular proportions of lime
putty to sand is:
1 part lime putty to 3 parts sand
Caution!
The durability of lime depends upon the.
quality of lime and the right mix, as well
as the quality of the application and the
drying conditions. Variables in the mix of
lime and sandincluding proportions
and the particle sizesare crucial, as are
the weather conditions during the
application process.
Apply in thin layers and make sure the
plaster is well keyed into the layer below.
If using lime to stabilize soil, always test
your mixture in advance. If not enough
lime is added, the compressive strength
can be lower than that of unstabilized
earth.
Do not overwork lime plaster with a
metal trowel. This makes lime come to
the surface and can form a hard crust
over a softer backing, weakening the
plaster.
Before application, make sure you cover
all metal surfaces, as the lime can stain.
Do not put lime plaster on top of
gypsum, wood, or latex.
WEATHERPROOFI NG AND F I NI S HES
When preparing the plaster, it is important
to mix and beat the lime putty for a long
time on a wooden or plywood surface with
wooden mallets and posts to get it to be-
come more plastic, and then work it well
into the sand. The more you mix, the bet-
ter the plaster.
Application
Make sure there is good adhesion between
the lime and the earthen plaster under-
neath. (Remember, before the earthen
plaster dries, to scratch its surface and
make finger-sized holes for "keying.") Tra-
ditionally lime-sand plasters have been
applied in two coats of not more than 10
millimeters thickness each. When apply-
ing lime plaster, the earthen plaster (or the
earth wall) underneath must be fully dried
out then slightly dampened to help the
lime grip the earthen surface. It is best to
use limewater for this (made by dissolving
2 to 3 percent of lime in the water).
After application of the first coat it
should be scored to provide key-in areas
for the second coat. This can also regulate
the shrinkage cracks. Noticeable shrinkage
in the first coat can serve as a warning that
either the lime is too fresh, the mix is too
wet, or the plaster is applied too thick; the
second coat should be thinner, as a safe-
guard.
The second coat should be applied
when the first is "green-hard"that is, too
hard to dent when pressed with a knuckle,
but soft enough to mark with a thumbnail.
Knock off any lumps around the score
marks and spray the first coat with lime-
water before re-coating. When the second
coat is hardening, it may be worked over
again to improve the finish, remove any
rough spots, and push closed any small
cracks. More detailed instructions can be
found in the book Lime in Building: A
Practical Guide by Jane Schofield (see the
bibliography).
Protect the plastered surface from sun,
wind, and frost to prevent it from cracking
during the drying process. It needs to dry
slowly. Ideal conditions are humid, cloudy
days with virtually no wind and a slight
drizzle. One way to provide protection
from the sun is to hang wet cloths a few
centimeters away from the plastered sur-
face. Frost can also be very damaging dur-
ing the drying period, and frost protection
may be needed for a minimum of two
weeks after the lime has been applied.
Pozzolanic Additives to Lime Plaster
Pozzolanic material can be added, ground
up into a powder, to speed the setting of
lime and to help the lime mix set deep in-
side the wall, which is necessary when us-
ing lime as a mortar in stone or brick con-
struction, or as a render directly on top of
earthbag walls where there are deep inden-
tations. Some examples of pozzolanic ma-
terials are crushed clay bricks, clay tiles,
shales, potash, and pumice. Pumice is a
naturally occurring pozzolan from volca-
nic areas. These pozzolanic materials
86 87
88
Recipes for Lime Mortars, Renders,
and Plasters
from the Earth Building Association, Devon, England
Mor t ar for Beddi ng
(can be applied as a first coat to earthbag walls)
12 parts coarse sand
3 parts lime putty
gauged wi th 1 part pozzolanic additive (for example, brick dust)
Roughcast Render : Backi ng and Fi ni sh Coat s
2 parts coarse sand
1 part grit (up to 4 millimeter diameter)
1 part lime putty
1 bucket mix to bucket of teased hair. Omi t hair in the final
thrown coat. Hair must be teased out wi th carding combs to
remove the large clumps.
S moot h Render
1 part coarse sand
1 part grit (up to 4 millimeter diameter)
1 part fine sand
1 part lime putty
1 bucket of mix to a bucket of teased hair
Li me/Manur e Render
1 part lime
4 parts wet cow dung (a few days old)
1 part sandy earth
Li me/Quar k Render
4 parts lime
1 part fat-free quark (to make quark, see the recipe on page 99)
10 parts sandy earth
Tallow, an animal fat, increases water resistance and adhesion.
Ten percent by wei ght of melted tallow can be added to
lime; this can also be replaced by linseed oil.
speed up the setting of lime due to the re-
active silica present in them, which com-
bine with lime at ordinary temperatures in
the presence of water to form stable, in-
soluble compounds with cementing prop-
erties. The rate of reaction is increased by
increasing the fineness of the pozzolanic
material (Spence & Cook 19 8 3) .
S T A B I L I Z A T I O N F O R
W A T E R P R O O F I N G
In addition to the water-resistant layers on
domes, extra protection is needed in ex-
tremely wet climates. Imperviousness will
help to reduce water erosion, swelling, and
shrinking when the plaster material is sub-
ject to successive wetting and drying
cycles. For waterproofing an earthen plas-
ter, a material that is unaffected by the
water that fills the voids, pores, and cracks
is required.
Bentonite clay is a material that is dis-
persed in the soil and that expands upon
the slightest contact with water and pre-
vents the infiltration of pores. This has re-
cently been tried as a waterproofing layer
in living roof construction (see chapter 5),
but its use is still at an experimental stage.
When used as a waterproofing layer, it
needs to be weighed down with a large
amount of soil, as it expands and moves
with absorption of moisture.
Bitumen is a mixture of hydrocarbons
and other materials, either occurring
naturally or obtained by distillation of
coal or petroleum. For instance, tar and as-
WEATHERPROOFI NG AND FI NI SHES
phalt are bituminous. The use of bitumen
as a stabilizer is very ancient, dating back at
least to Babylon in the fifth century B. C. E. ,
where it was used for making mortar or
laying unbaked molded bricks. Bitumen
mixed with soil acts as a water-repellent,
reducing penetration and surface erosion
from wetting, therefore serving more as a
waterproofing element than a binder. It is
most successfully used with granular soil,
in which it improves durability, but is also
widely used with clay soils, for instance in
the manufacture of adobe bricks. Stabili-
zation with bitumen is in fact most effec-
tive in a process involving compression, as
in production of compressed clay blocks.
To stabilize adobe, 2 to 3 percent of bitu-
men can be sufficient, and sometimes as
high as 8 percent is required. If used as a
stabilizer, bitumen either must be mixed
with solvents or dispersed in water as an
emulsion. If used with soils containing
high proportions of clay, a larger amount
is required due to greater resistance to
mixing. To obtain an even distribution,
large quantities of water need to be used.
Solvents that can be used include diesel oil,
kerosene, naphtha, and paraffin (a mix-
ture of 4 to 5 parts bitumen to 1 part paraf-
fin oil).
Note that these solvents cannot be used
in the rain and are flammable. Also, bitu-
men stabilization is not effective in acid,
organic, or salty soils.
A simpler, more natural weatherproof-
ing solution can also be made by mixing
clay with pure linseed oil and applying it
onto earthen plasters.
S T A B I L I Z A T I O N W I T H C E M E N T
Cement should only be used as a stabilizer
in plasters as a last resort in cases where the
soil does not contain enough clay and
other, more natural stabilizers aren't avail-
able. For instance, if lime is not available,
soil stabilized with cement can be used on
polypropylene earthbags containing sandy
fill with little or no clay. Cement interferes
with the binding forces of clay; therefore,
care needs to be taken when deciding on
the quantity of cement to be added to your
soil; the higher the clay content, the more
cement is needed. Somewhere between 3
and 10 percent will probably be appropri-
ate, but tests should be carried out to de-
termine the necessary quantity more pre-
cisely (see chapter 7 for more informa-
tion).
If cement is used, commercially avail-
able Portland cement has the least embod-
ied energy (that is, it requires the least en-
ergy for processing and preparation). It is
made of burned lime and highly reactive
silica. It introduces a three-dimensional
matrix into the soil and results in a filling
of the voids with an insoluble binder,
which coats the grains and holds them in
an inert mass.
While a cement-stabilized render can in
some cases be used over earthbags, for in-
stance soil cement or conventional stucco
finishes, never use cement plaster on top of
89
9 0
Chunks of cement
plaster cracking off an
adobe wall of the
monastery in Abiquiu,
Santa Fe, New Mexico.
adobe or cob walls or a nonstabilized
earthen plaster!
As emphasized repeatedly in this chap-
ter, when cement plaster is applied on top
of earth, it forms a brittle, rigid surface
that is impervious to moisture. The effec-
tiveness of cement-based plaster is depen-
dent upon the rigidity of the wall beneath
it, since the cementitious finish itself
forms a rigid, relatively brittle shell. An
earthen wall continues to move over time;
this is normal, and is even beneficial in
seismically active areas. Due to the differ-
ent properties of cement and earth, tem-
perature changes and moisture cycling
tend to produce cracking in the cement
render. These hairline cracks could be al-
most invisible, but once the waterproof
finish is compromised, any moisture
drawn in through these tiny cracks will be
trapped, unable to evaporate, and will
start wearing away at the softer material
behind. Given enough time, big cavities
can be worn away, even across the whole
width of a wall. This would not be such a
problem if the damage were detected early
enough, as the wear is very gradual. But the
surface of the cement-based plaster does
not wear very noticeably, therefore hiding
the problem until entire chunks of wall
cave in or collapse.
Such moisture damage is most likely to
occur where hard, modern materials are
applied as a finish to a building whose un-
derlying structure is made of softer, more
flexible earthen materials. A lime-based
render or earthen plaster acts more like
blotting paper, absorbing and releasing
moisture relatively freely. In addition ac-
cording to the Devon Earth Builders, small
cracks may be closed by redeposition of
soluble material from the lime or clay.
Carol Crews of New Mexico's Gourmet
Adobe explains the large lesson learned at
the famous St. Francis de Assisi Church in
Ranchos de Taos:
When it was coated with cement
stucco in 19 67 this plaster cracked
and allowed the moisture to pen-
etrate deeply into the adobes, but
the relatively impermeable stucco
prevented the adobes from drying
out again. Large sections of the
buttress had to be rebuilt, so the
community has now gone back to
the annual renewal of the mud
plaster, which not only keeps the
church building in beautiful condi-
tion, but strengthens neighborhood
ties as well. (Kennedy 1 9 9 9 , 9 5)
It is surprising that even after experi-
ences of this kind, the U.S. Uniform Build-
ing Code continues to stipulate the use of
cement plasters on top of the adobe walls
in several of the Pueblo Indian villages in
New Mexico. With cement-based renders,
a great deal of work is still required for
maintenance, but often the result is a
patchy surface, since repairs with cement
plasters are usually visible. Instead of being
WEATHERPROOFI NG AND F I NI S HES
9 1
allowed to simply give each house a thin
coat of earthen plaster or whitewash once
a year, the buildings have to be carefully
and expensively repaired.
As a general rule: Renders should have a
permeability equal to or higher than that of
the wall material.
A P P L I C A T I O N O F S T A B I L I Z E D
R E N D E R S
With the addition of some stabilizers the
render applied to the domed or vaulted
parts of the structure becomes more
brittle, and cracks can occur through ex-
pansion and contraction with extreme
temperature changes, as discussed above.
This movement can be controlled through
the fragmentation of the render mass. By
placing the render in small "patties," a tex-
tured finish can provide thermal variation
throughout the whole surface of the struc-
ture, creating air movement due to the
temperature differential between the sun
zone and shade zone within the render it-
self, never allowing the surface to overheat.
As one side of a rounded patty heats up,
the other cools down. This surface has
been used for centuries in African villages
and is prevalent in nature, for example in
the scales of a fish or the trunks of trees.
Application
Once you have chosen the right stabilized
mix (clay, lime, cement, etc.), apply a
"scratch" coat to fill in large cavities and
create the desired overall shape. Leave any
Top: The textured, stabilized render applied to the waterproof layer (roofing felt)
on a vault in California.
Inset: Textured surface of a vault.
Bottom: Fragmented "patties" of cement-stabilized soil placed directly on the
surface of the earthbag dome, California.
irregularities in the surface so the second
coat has somewhere to key into. To
achieve the bubbly effect, patties of stabi-
lized soil are placed like roof tiles, overlap-
ping each other, starting at the base (like
laying tiles) and working up the structure.
Stagger the cracks so water will run down
the grooves (see the photo on page 91 ).
I N T E R I O R F I N I S H E S
There are many ways of finishing the in-
sides of earthbag walls, but whichever
method is used for the final coating, it is
best to coat the uneven earthbag surface
with an earthen plaster to fill in any large
cavities before the other layers are applied.
As discussed above, lime mixed with
very fine sand is a great material to use on
top of interior earthen plasters. Another is
gypsum. Gypsum is a naturally occurring
soft rock or powder. It is converted to
"plaster of Paris" by heat. Gypsum is
readily available at building supply stores,
and it can be applied directly on top of
earthen plaster, since it is breathable. Due
to its softness, it can only be used on inte-
rior walls. It doesn't shrink or crack when
dry and sets very fast, which can be an ad-
vantage or disadvantageyou need to
work fast when applying it to a wall, but
the technique is not hard for nonprofes-
sionals to learn. Gypsum is acidic, and has
a low embodied energy compared to Port-
land cement, but in premixed form it is
relatively expensive. Gypsum plaster can
also be mixed as 1 part gypsum to 2 parts
sand for more texture and lower cost, or it
can be combined with perlite for a more
lightweight, better-insulating mix. Pig-
ment can be added for a more colorful
outcome. Gypsum can also be mixed with
lime putty to create a faster-setting plaster
than lime alone.
As an alternative to two coats of con-
ventional plaster for walls and ceilings,
clay mixed with sand and fiber may be
more appealing. (See chapter 7 for more
on mixing clay plasters.) Clays come in
many different colors, and beautifully col-
ored finishes can be achieved using only
the earthy clay colors, for there is seldom a
problem with the colors clashing. Mica
can also be added to a final coat of clay
paint or plaster, which will add a glittering
texture.
Earthen plasters are usually applied
with hands or a wooden trowel, but for
larger projects you can use a hand-held
spray gun powered by a gas-driven com-
pressor. Screen the mix through a 1/8-inch
screen to eliminate any lumps that might
clog the machine. This spray mix is often
made with wheat flour paste as a stabilizer
(see page 96 for the wheat flour paste
recipe).
S E A L A N T S
Sealants can also be used as nonstructural
stabilizers, but they are called sealants be-
cause they seal the earthen plasterthat
is, they are not mixed into the plaster dur-
ing the construction process but are ap-
plied like a paint or a finish plaster once
the original plaster has dried.
93
There are two types of sealants: those
that form a skin or a shell, and those that
penetrate deeply into the earth. Sealants
that form a skin or a shell are fine, as long
as they breathe (lime is an example of one
that does). The main problem with "skins"
is that they create a thin hard cap on top of
a relatively soft surface, which can be easily
damaged under pressure. On surfaces
where pressure is constantly being ap-
pliedas on an earthen floorthe right
choice of sealant would be one that pen-
etrates deeply into the earth rather than
forming a shell-like surface. This is why,
when sealing an earthen floor with linseed
oil, it helps to heat the oil to make it soak in
as deeply as possible. To encourage the oil
to penetrate even deeper into the floor, it
can be thinned with various thinners (see
"Earthen Floors" in chapter 7 ) . Good seal-
ants include penetrating oils such as lin-
seed, hemp, caster, or coconut, and animal
urine and blood, all of which oxidize and
harden the surface.
Certain sealants may be mixed and ap-
plied as one layer, but different sealants
should never be layered over one another,
as they could be incompatible and peel.
Binders such as clay can also be used as a
waterproof sealant in their finer forms,
but too much pure binder will not be du-
rable. Filler (sand, silt, or gravel) should be
added to it to make it solid and hard.
Sodium silicate dissolved in water is
known as water glass. Water glass can be
used as a sealant with certain soil types, but
has been known to react very differently
Interior of a cassita in
Canelo, Arizona. The
walls have a clay finish
with mica for shine. The
white bench is
plastered with gypsum.
Cedar Rose
demonstrating the
spraying of a mud
mixture at the Natural
Building Colloquium,
Kingston, New Mexico.
WEATHERPROOFI NG AND F I NI S HES
9 4
with varied mixes of earth. It is not suitable
for clay soils, but has proved useful with
sandy soils. Sodium silicate is fairly cheap
and is available in many parts of the world.
It acts as an impermeablizing agent after a
curing period of seven days. It is soluble in
water, but can be rendered insoluble by al-
lowing it to react with slaked lime. Thin
sodium silicate with water prior to mixing
with earth, otherwise too many "micro fis-
sures" will result, causing a strong suction
of water. Another silicate used to make
plasters impermeable is potassium silicate.
Potassium silicate can be dissolved in wa-
ter to make a liquid, then used to seal and
waterproof mud plaster. The coating is
clear in color, allowing the full beauty of
the plaster to show. When put on top of
lime plaster, potassium silicate reacts with
the calcium in the lime and the carbon di-
oxide in the air, creating an impervious
layer. Potassium silicate is made out of
quartz sand and potash and binds itself
chemically with silica when applied, which
is good for surfaces that contain sand. Sili-
cates also bind mechanically in grooves in
the surface of the plaster.
Before applying, thin silicates with wa-
ter: for example, 1 part potassium silicate
to 5 parts water.
P A I N T S
As well as plastering earthen walls on the
inside, you can coat them with "breathing"
paints to give extra protection or color. I
learned about this subject from Swiss
painter Reto Messner. Natural paints de-
rived from plant and mineral materials
have subtle colors, pleasant scents, and
help create a healthy indoor environment.
Since only a few decades ago, the petro-
chemical industry has largely taken over
production of oil-based and water-based
paints. They not only abandoned the tra-
ditional view of paints as a breathing skin,
but have also introduced synthetic chemi-
cals that can be very harmful to us. In ad-
dition to being concerned about the pollu-
tion generated by industrial paint manu-
facturing, increasing numbers of people
find themselves affected by the vapors
given off by modern paints as they dry,
and even by the low levels of volatile or-
ganic compounds (VOCs) that continue
to outgas afterward. Sick building syn-
drome has now been widely recognized to
be the result of modern synthetic materi-
WEATHERPROOFI NG AND FI NI SHES
95
als in combination with poor ventilation; this phenomenon can
damage the health or at least affect the comfort and performance
of people living and working in newer buildings.
Like cement, modern waterproof masonry paints, emulsion
paints, and vinyl wallpapers all slow down or prevent the evapora-
tion of moisture from the wall, which often leads to the render or
paint separating from the surface of the wall, and water trapped
between the wall and the paint can be harmful to the wall itself,
especially if the building is constructed of materials such as wood
or earth that can deteriorate when wet.
Paint consists of pigments, extenders (also known as fillers), and
binders. Pigments and extenders comprise 7 5 percent of the total
quantity of paint. Binders comprise 25 percent. Pigments color the
filler. They can be different minerals or plant powders. It is better
to use water-based paints on walls, because these allow for vapor
diffusion and breathability. Extenders are a kind of paint "filler."
Extenders can include whiting, obtainable at paint or ceramic
stores; barium sulfate; kaolin; marble dust; chalk; and diatoma-
ceous earth.
Binders can be water based or oil based, depending on the re-
quirement. Examples of water-based binders include clay; casein
(milk protein), which is very strong when dry and will not come
apart; water glass; lime cellulose glue; starch glue (corn starch) or
wheat paste; and lime.
Limewash, also called whitewash, is a water-based paint that has
been used for centuries, ordinarily re-coated every year or so. Ad-
ditives to limewash to make it more durable (but less breathable)
include linseed oil, tallow; and proteins such as egg white, blood
plasma, or casein. See page 9 7 for a more detailed discussion of
lime paints.
Painting with clay paint over an earthen plaster on a
straw bale wall in Casa Chika, Kingston, New Mexico.
C L A Y S L I P O R A L I S
Alis is a clay-based paint traditionally used over earthen plasters on
the interior of adobe houses. Alis can be of any desired color, and
when dry it makes a durable finish. I learned about alis from Carol
Crews of Gourmet Adobe in Taos, New Mexico.
The Steens' residence,
Canelo, Arizona.
96
An earthen plaster
shower wall painted
with lime, Canelo,
Arizona.
If white alis is desired, Carol uses white
kaolin clay as the binder, because it is inex-
pensive and can be purchased in large bags
from a pottery supply store. She uses
ground mica in a fine powder form or fine
sand as the extender, and straw or mica
flakes for added texture and glitter. To
make the paint thicker, especially in the
first coat, a small amount of fine sand is
added to smooth out irregularities in the
plaster surface. As filler, Carol uses cooked
flour paste in a proportion of 20 to 25 per-
cent of the liquid. Pigments or colored clay
can be added to white alis to give it color.
To Cook Wheat Flour Paste
Set a pot two-thirds full of water to boil on
the stove. In a mixing bowl, whisk together
another one-third proportion of cold wa-
ter with some flour to a consistency of a
pancake batter. When the pot of water is
vigorously boiling, pour in the flour-water
mixture to make the pot almost full, and
stir the mixture well.
It should thicken immediately and be-
come translucent. Take it off the heat.
The total proportion of water to flour
should be about 6 parts water to 1 part
flour paste. For mixing the plaster dilute
this wheat paste to a good consistency.
To Make Alis Clay Paint
Fill a 5-gallon bucket three-fifths full with
3 parts water to 1 part cooked flour paste.
For the first, slightly thicker coat, add
to the diluted flour paste liquid a mix of 3
parts clay to 2 parts mica to 1 part fine sand.
(If no mica is available, substitute fine
sand.) Keep adding these proportions un-
til the mixture is the consistency of heavy
cream.
For the second coat, add to the diluted
flour paste a mixture of 1 part clay to 1 part
mica. Again, keep adding these until the
mixture is the consistency of heavy cream.
A little powdered milk (with casein)
will thicken the mixture and makes it
somewhat tougher. Some finely chopped
straw or large flakes of mica can be added
for an interesting texture. Colored clays or
pigments may also be added to create dif-
ferent colors. If colored clays are added,
they can replace some or all of the kaolin in
the recipe. If mold is a problem, it is advis-
able to add some dissolved borax powder,
which will make the paint alkaline.
WEATHERPROOFI NG AND FI NI SHES
9 7
Application
Before application, make sure the wall sur-
face of your earthen plaster is totally dry, as
any moisture could leave water stains in
the finish. Start applying the paint with a
brush at the top of the wall so you do not
get drips.
Most walls require two coats. Make sure
the first coat is completely dry before the
second is applied. When the second coat
becomes "leather hard," take a damp
(squeezed-out) sponge and a bucket with
warm water and start to sponge the wall in
circular movements. This will smooth out
the brush strokes and clean the paint of
any pieces of straw or flakes of mica that
might have been added to the mix for spe-
cial effect. When the sponge begins to feel
dry, wet it and squeeze it out again. When
you are finished, you can save the leftover
paint for later repair to any minor damage
by drying it out on a tarp in "cookies." To
reconstitute, simply add water to the dried
paint until the appropriate consistency is
obtained (Kennedy 1 9 9 9 , 9 3) .
L I M E P A I N T O R W H I T E W A S H
If possible, find a source for ready-made
lime putty (matured for a minimum of six
weeks), as this is the easiest, safest way to
buy the material, or mix bagged hydrated
lime. Limewash is lime putty and water
(see page 8 4 for more on lime putty). Mix
the putty and water together to a consis-
tency of skimmed milk. Sieve through a
fine kitchen sieve. If pigment is desired, be
sure that it is thoroughly premixed by add-
ing it to a little warm water in a jam jar,
then seal the jar's lid and shake vigorously.
Add the pigment to the limewash, and stir
and sieve it again. To get a really white fin-
ish over an earthen plaster, you will prob-
ably need at least three coats. Limewash
turns very white only when it is dry, and if
pigment has been added, the final coat will
turn about seven times lighter than when
it is liquid. Always wet the surface of the
earthen wall before applying a limewash.
Additives to Limewash
These include:
casein glues, or flour paste, as
binders
salt, to improve durability
molasses, to increase penetration
into an earthen wall
alum, to improve adhesion
linseed oil or tallow, to increase
water resistance
Recipes for Water-Resistant Whitewash
Whitewash with oil or tallow. For exterior
surfaces, the addition of linseed oil or tal-
low (animal fat) makes the whitewash
more resistant to water. According to "Ap-
propriate Plasters, Renders and Finishes
for Cob and Random Stone Walls in De-
von," published by Devon Earth Building
Association, use no more than 1 table-
spoon of linseed oil or tallow for 2 gallons
of whitewash. Add the oil when the lime
Natural
Putty
Mix chalk and
linseed oil, and
knead until well
stirred and stiff.
Add earth or
plant pi gment as
desired, and use
for filling gaps
and puttying
wi ndows.
and water are slightly heated. Continue
stirring and heating slightly until the mix-
ture has blended.
Whitewash with linseed oil and milk. To
increase the water resistance of white-
wash, fill a container with 4 quarts of
milk, add 1 cups of linseed oil, and stir
well. Add lime and stir continuously un-
til the mixture is creamy, of a paintlike
consistency.
Some Old Limewash Recipes
If you are interested in trying out working
with lime in a more primary form instead
of premix, here is a recipe for a brilliant
whitewash that will not rub off, and which
bears a gloss like ivory. Take 5 or 6 quarts
clean unslaked lime, slake with hot water
in a tub, and cover securely to keep in the
steam that's generated by the slaking.
When the lime mix is ready, pass it
through a fine sieve, and add pound
whiting, 1 pound good, pulverized sugar,
and 3 pints rice flour, first made into a thin
paste. Boil this mixture well, then dissolve
1 pound clean glue in water, and add this
solution to the mixture. You may also add
coloring matter to give the mix any shade
you please. Apply the limewash while still
warm, with a whitewash brushexcept
when particular neatness is required, in
which case use a paintbrush.
This recipe is from a book by Sam
Droege first published in 1861 and found
on the Internet (see the bibliography).
To make whitewash that will not wear
off, make the whitewash in the ordinary
manner, but then place it over a fire and
bring to a boil. Then stir into each gallon a
tablespoon of powdered alum, pint of
good flour paste, and pound of glue dis-
solved in water while it is boiling.
This wash looks as good as paint, is al-
most as durable as slate, and will last as
long as paint. The recipe comes from the
Building Biology and Ecology Institute of
New Zealand (see the resources list).
C A S E I N
Casein can be used as a binder or stabilizer,
to make paints more durable and weather
Casein Glue
Here is an old recipe for casein glue.
Mix skimmed-milk curds (quark) well wi th 2.5 percent quicklime. Use after one hour. Apply to
both surfaces to be glued together and set under pressure for twenty-four hours. The mixture
should be remain useable for about three days on wood, cork, paper, or heavy wallpaper.
WEATHERPROOFI NG AND F I NI S HES
resistant. When it is mixed with an alkaline
substance such as borax, it will react and
form a gluelike solution that can be used as
a binder in paints or plasters, or as an ac-
tual glue (see page 9 8 ). If the casein paint is
used on top of lime plasters it does not
need to contain borax, as the alkalinity in
the lime will activate the casein.
Casein can be purchased. One com-
mercial brand is called Auro (see the re-
sources list). You can paint your house us-
ing about 2 pints of casein, as it goes a long
way. You can also make your own casein
with simple ingredients.
To make casein (also known as quark or
milk curds) at home for use as the binder
in paint:
Mix 1 quart nonfat or 2% milk and 2
teaspoons low-fat sour cream. Stir well.
Let sit in a warm spot for two days until it
thickens or curdles. (If it does not curdle,
warm it up or add vinegar to make it
curdle.) Separate the curds from the whey
by pouring the mixture through cheese-
cloth placed in a sieve.
What you have left is known as quark,
which contains 7 to 12 percent casein, the
right proportion for use as binder in the
paint. Do not leave this mixture to stand
for too many years, as casein loses strength
with time.
Recipe for Interior-Exterior Casein
To make a durable casein glaze or paint
that can be used inside or outside and not
wash off in the rain:
Mix together cup (2 ounces) casein
powder with 3 ounces of warm water, and
ideally let sit for two hours or overnight.
(If homemade quark is used, it does not
need to be mixed with water.) Mix the
casein solution with cup (4 ounces) of
borax dissolved in cup (4 ounces) of
warm water to produce the binder mix-
ture. (Borax is an alkaline soap; do not
dump in your garden.) This mixture will
become a sticky paste and is also know as
casein glue, which will lose strength over
time and must be kept refrigerated.
To this casein binder add 8 cups of wa-
ter and mix until the solution is like pan-
cake batter. This can be used as a durable
glaze or paint. (The binder mix when di-
luted can also be used to mix a durable
plaster.) When making transparent paint
(a glaze) for use on top of a lime plaster,
you do not need to add borax, since the
lime will activate the casein.
To make this glaze into an opaque paint,
mix pigment with an extender such as
chalk or any other inert white powder to
make a paste. Then add this mixture to the
binder in a ratio of 25 percent binder to 7 5
percent extender with pigment.
You can also make a water-based casein
emulsion that is more water-resistant us-
ing quark and lime. Mix a quantity of
skimmed-milk curds (quark) with about
20 percent lime to obtain casein glue, then
thin with water until it becomes a creamy
brew. This can be used for several days.
Add 2 to 3 percent linseed oil to increase
9 8
99
adhesion and durability, especially for ex-
terior application. In addition, you can
also use diluted casein paint as a primer,
which will increase durability furtherno
wiping off after only a few weeks. Another
way to improve the adhesion of this paint
is to add honey to 100 parts curd, 50 parts
water, and 20 parts lime.
Application
If casein paint is sucked into the plaster
right away and the desired effect is to be a
glaze, it is necessary to prime the wall first
with a thin mixture of casein binder and
water, and allow it to dry. When the paint is
applied the water in the paint should be
absorbed, but not immediately. As a prim-
ing binder, alum is especially appropriate
for gypsum-plastered walls. If the paint
continues to dust off, it does not contain
enough binder, or the wall is not primed
properly. Too much binder can create a
glassy surface, which can flake off.
O I L - B A S E D P A I N T S
Linseed oil (from flaxseed) is a good oil to
use in oil-based paint. This is a "stand oil,"
which is an important factor in making
oil-based finishes, because it oxidizes
and drieswhen exposed to oxygen. Ac-
cording to the Canelo Project's Earthen
Floors booklet (see the bibliography), in
the "old days" oils were left to stand ex-
posed to the air to produce the drying ef-
fect. However, they can now be produced
by injecting oxygen into the oil. Linseed oil
is reasonably water resistant, but if ex-
posed for a long time to moisture will
eventually deteriorate.
To make oil-based casein paint, add oil
to a casein binder (see the recipe above)
very gradually, as in making mayonnaise.
Mix a maximum 25 percent of volume of
oil into the mixture; 15 percent is usually
good, so test the paint on a sample patch
before more oil is added for shine. The
mixture will eventually start to get creamy.
To make casein- or oil-based limewash,
mix 1 ounce limewash (lime putty mixed
with water) and 5 ounces casein powder or
1 ounces linseed oil.
Paint this limewash onto fresh lime
plaster that is not totally dry. You must use
thin coats. It is best to use linseed oil for the
first coat, followed by casein, because casein
limewash is harder than oil limewash.
M A I N T E N A N C E
The annual maintenance requirements for
a plastered building depend on the nature
of the finishes that were used. If the plaster
finish is made of earth, maintenance is re-
quired at least every two years. A thin coat
of earthen plaster should be reapplied on a
dampened wall surface. This is best carried
out during the summer months. If earthen
plaster has been sealed with a capping of
lime plaster, an annual fresh coat of white-
wash will maintain the finish well, but this
is not absolutely necessary, as well-ex-
ecuted lime plasters will last many years
before they need to be repaired.
WEATHERPROOFI NG AND F I NI S HES
Remember, cement plasters are very
brittle and will tend to crack due to subtle
movements of the whole structure, there-
fore requiring repair. Repairs of cement
stuccos and renders will always be visible
unless the whole area is repainted.
Papercrete (fibrous cement made of cel-
lulose mixed with cement or lime; see chap-
ter 1) can also be applied as a plaster directly
on earthbags. Papercrete is still at its ex-
perimental stage, but this seems to be a
material that is water-resistant (not water-
proof), therefore suited to most climates;
insulative; and not as brittle as cement ren-
der, therefore it might not crack as much
and may be easier to apply and repair.
The wear of the finishes is affected sig-
nificantly by the materials you choose, the
quality of the application, the location of
the house, as well as the overall design of
the house and whether there are any chil-
dren or animals around, in which case
more house maintenance is generally nec-
essary. Annual replastering does not have
to be a chore, but can be turned into a fun
social event involving the whole family or
even the neighborhood.
1 0 0 1 0 1
7
OTHER INTERIOR WALLS, FLOORS, AND FURNISHINGS:
BUI LDI NG WI T H CL AY
O
nce the structure of an earthbag
house is complete, it is possible
for the interior of the house to
have conventional furnishings, just like
any other house. More often, however,
those who have gone to the trouble of find-
ing out how to build an earth house are in-
terested in using natural materials and
earth-based techniques for completing the
interior, in order to create an especially
healthy and beautiful home. This can in-
clude partition walls, ceiling treatments,
insulation, floors, and furniture. In this
chapter, I refer to building materials and
techniques such as clay-earth mix, straw-
clay, cob, and adobe, which were intro-
duced in chapter 1. In describing these
techniques, I emphasize the need for clay
as a binder, as this is the most crucial in-
gredient when building elements that
must maintain their structural integrity
without exterior forms. Clay generally
binds together filler materials such as sand,
straw, and earth.
The advantage of using earthen materi-
als for furnishings on the inside of a house
stems not only from the beauty and health
benefits of earth, but also its ability to
adapt to any shape. In a circular earthbag
dome shape, where straight and square
furniture can be difficult to accommodate
and expensive to custom-make, earthen
materials are more flexible and less expen-
sive, allowing you to design the interior in
a complex or simple way, using straight
lines or curves as desired.
F I N D I N G A N D A N A L Y Z I N G
B U I L D I N G S O I L S
As we consider guidelines for soil analysis
prior to building with clay-earth mixtures,
readers will once again appreciate earth-
bag construction for its simplicity, as there
is no need to understand the complexity of
the soil and its clay content, since the bags
themselves provide a form to hold the
earth in place, whereas when building in-
terior partitions, benches, ovens, and
earthen floors, the binder-to-filler propor-
tions are critical, because these structures
need to maintain their own form, with no
bag or other exterior form to hold the
shape.
Due to the vast variety of soils, there are
no universal recipes for making good clay-
based mixtures such as cob or adobe. You
Facing page: Earth-
plastered shelving
being constructed with
straw-clay blocks and
carrizo decking.
103
can ask the people who have already built
in the area where you want to build what
mixtures have worked for them. It is cru-
cial to know your soil before using it for
construction. For this, homemade tests
can be carried out. There are several char-
acteristics to look for, including particle
size (ranging from fine silt and sand up to
rough aggregate such as gravel), plasticity
(the capacity to retain a shape, which per-
mits sculpting of the material), compress-
ibility (to increase adhesion, especially
important with techniques such as pro-
duction of compressed adobe blocks), and
acidity or alkalinity (which affects the way
various materials combine).
Prior to beginning to build with earth,
it is important to understand the best ways
of finding, extracting, and mixing the
most resilient blends of clay and other
materials. The soil should be obtained
from below the topsoil line (topsoil is for
gardens), and must be free of all organic
matter.
There are a number of ways to find clay.
Many conclusions may be drawn from the
geological situation. Purchase geological
maps of the area or visit the geology de-
partment of a university or a government
institution to request assistance. Consult
local brickmakers or potters, who are nec-
essarily very conscious of fine distinctions
among earthen materials. Investigate the
availability of clay on conventional con-
struction sites, where clay is often dug up
during excavation and transported to a
dumping ground, which might be far away
and therefore incur extra charges. If you
can take this "waste" material off a
builder's hands, you may be able to obtain
clay for a good price. Certain plants indi-
cate the presence of clay soils. For example,
the group of plants called horsetail or
scouring rush (Equisetum) suggest clay
soils (Andreson 1 9 9 7 . When the earth is
very dry and many irregular cracks have
appeared on its surface, this indicates the
presence of clay. This is easily seen at the
bottom of puddles or dried-up ponds.
Other landscape clues for the presence of
clay are described in Michael Smith's
book, The Cobber's Companion (see the
bibliography).
The best way to begin to know your soil
is by making several tests with samples.
Jar Test
Pour several handfuls of earth into a large
glass jar half full of water. Shake the jar well
and let it sit until all the particles settle.
The heaviest particles, such as rocks and
A jar test to estimate percentage of clay in a soil
sample.
BUI LDI NG WI TH CLAY
pebbles, will settle at the very bottom of
the jar. Then the sand and the silt (which is
a finer version of sand) will settle, leaving
the clay (the smallest particles of earth) as
the top layer. From this simple test we can
estimate the percentage of clay in the soil.
Testing by Hand
There are numerous tests that can be car-
ried out on soils to check if clay is present.
Rolling and pressing the clay between the
fingers will give an indication if the soil
contains any clay. If a thin "sausage"
(about inch or 4 millimeters thick) can
be rolled and does not crack very much
when slightly bent, the earth contains high
quantities of clay. If it cracks, it probably
contains a larger quantity of silt. Another
way to test soil by hand is to make an egg
shape, then crack it. If it resists cracking, it
is clay, whereas if it cracks easily it is
mainly silt or other more granular par-
ticles of soil.
T H E R I G H T M I X
A good construction material must have
clay and sand in the right proportion. The
more filler that is mixed with the clay, the
more evenly distributed the cracks that re-
sult from drying will be. The more the
straw is added, less sand may be needed,
because straw takes up the shrinkage,
therefore stopping the cracks.
Always make samples, since this is one
of the most effective ways of being sure of
your soil's limitations. A set of samples
should be made into small patties or adobe
blocks for comparison.
The first sample should be pure earth,
to be used as a control, followed by samples
with 10, 20, and 30 percent of added sand.
Repeat the test, adding fibers such as straw,
grass, hair, or textile strands, and then add
both fibers and sand in varied propor-
tions. If the soil has a high clay content, you
may need to add more sand as a filler or
more fiber to inhibit cracking.
When a sample indicates a good mix for
building, it will not crack. But not all
cracks are bad. For adobe, the California
Building Code allows cracks up to 2
inches (7 centimeters) long and 1 inches
(3 centimeters) wide (Khalili 1986). When
dry, a promising sample can be tested by
twisting it with your hands to try to break
it, or by dropping it from knee height. If it
does not break upon impact, then the
earth mix is right.
If the local soil does not contain enough
clay to bind together properly, it is possible
that stabilizers are required. These need to
be tested at this stage by being added into
the mixture in varying quantities.
To answer the question of what makes a
good building mix, here are a few pointers,
although it is important to note that every
mix should first be tested by making small
samples and observing them when dry,
prior to any application.
To form a durable surface and create a
mix sticky enough to adhere, you may
-floating organic matter
clay
silt
sand
water
gravel
1 04 105
need to mix more thoroughly, increase
the clay content, and/or add some
type of stabilizer.
To minimize shrinkage and therefore
cracking, you can reduce clay, add
more sand or other aggregate, keep
water content as low as possible, or
add more fiber such as straw and
other grasses, cellulose, or other plant
or animal fibers.
To increase water resistance as much
as possible and slow down erosion by
driving rain, you can add a good
distribution of aggregate sizes, fibers
such as straw, and/or stabilizers
derived from plant, animal, or mineral
sources (see chapter 6).
To increase the permeability and
porosity of an earthen mix, which are
necessary to permit moisture to
evaporate and to allow for expansion
of freezing water in order to avoid
frost damage, an earthen mix needs
a good distribution of aggregate,
straw, and anything else that will
create air gaps.
If you are carrying out sample tests with
stabilizers and are not getting the results
you might expect, try testing the pH of the
soil, as not all stabilizers react with soils of
all types. For example, if the clay is more
acidic, it should react beautifully with
lime, an alkaline, forming a more neutral
and creamy mix for an external render (see
chapter 6 for more on stabilization).
You will also want to carefully control
the type and size of filler or aggregate that
you use, taking into consideration the in-
tended function of the mixfor example,
whether it is for the structure of furniture,
the filling out or evening out of a base plas-
ter, or the final smoothing out of a finish
plaster. The finer the desired appearance,
the finer the added aggregate, filler, and fi-
bers need to be.
Also, a more structural earthen mix can
have a large range of particle sizes, from
silt to gravel, as the filler material, and "fill-
ing in," "evening out" plasters can be made
using more of the long straw additive in
order to be more reinforcing and provide
more sculptural capacity. The final layer of
plaster can have just fine sand mixed in
with the clay, as well as finely chopped
straw and stabilizers if desired.
My own favorite mix for a thick first
coat of plaster and for sculpting is quite
simple and works with most clay soils. In a
wheelbarrow (as described on page 108 )
combine a soupy mixture of clay soil with
as much long or chopped straw as the mix-
ture can take and still stick together, along
with just enough sand to give it some body
and prevent hairline cracks for the finish-
ing layer. (Chopped straw will be easier to
manage than long straw during smooth-
ing.) If the first layer is fairly thick and
even, the second layer can be thin, with
more sand substituted for straw, and in-
side the house a stabilizer such as wheat
paste added.
BUI LDI NG WI TH CLAY
1 07
According to Devon Earth Builders,
traditional English cob mix contains clay
and aggregates in the following propor-
tions:
fine course sand
silt
clay
25-30%
10-20%
10-25%
It will also contain fibers (as much as
the mix can take without ceasing to ad-
here) to reduce cracking and increase the
insulation value. Sufficient straw in the
mix provides a level of thermal insulation
that is better or equal to the insulation in
many conventional houses. In England,
traditionally the fibers used were wheat
and barley straw along with hay, twigs, and
other organic material including animal
hair and animal dung.
Correct mixing of the material is as im-
portant as the actual construction process.
If too little water is added, the necessary
distribution of clay throughout the soil
will be difficult to achieve, and the cob
lumps will be difficult to compact when
placed on the wall. In the past, compaction
was achieved using the worker's boot, so
that each cob is well heeled-in and thor-
oughly trodden between each course. Ex-
cessive moisture dilutes the soil to a
porridgy state, making construction im-
possible; in such cases, more dry mix and/
or straw can be added.
Getting the right mix for earthen plas-
ter, floors, or furniture and making adobe
or cob for building is all principally the
same process. The ingredients might vary
slightly, but once the recipe for a particu-
lar type of earth is established, these pro-
portions can be used for any of the above
techniques. The ingredients might include
varying proportions of straw, depending
on the coarseness of the earth and sand.
Earthen plasters or floor finishes will re-
quire the mix to be sifted, for a finer finish.
Cob for building may require more straw
than adobe requires.
Many different ways have been devel-
oped throughout the years in different
parts of the world, but they all have the
same aimevenly distributing the vari-
ous materials that make up the mix and
creating a moist, pliable mass of earth.
A cob shelter built
during a workshop led
by Sunray Kelly and
Carol Crews, Rico,
Colorado.
i o6
108
Mixing with bare feet.
In the traditional way developed over centuries in Devon, En-
gland, once proportions are identified through testing and making
samples, the desired earth mix is
spread out in a bed approximately 100 millimeters in depth
on a thin layer of straw. Water is then added and a second,
thicker layer of straw is spread evenly on top. (About 25 kg.
of straw per cubic meter of soil1.5 to 2 . 0 % by weightis
considered adequate.) The straw is then trodden into the
soil, which is turned several times, more water being added
as required. Thorough treading of the mix (traditionally by
men or animals) is vital because it ensures even distribution
of the clay and renders the material to a consistency and a
state of cohesion suitable for building. The quantity of water
used will vary according to soil type but is usually in the
range of 10 to 1 2 % by weight. If too little water is added the
necessary distribution of clay throughout the soil, will be
difficult to achieve. (Devon Historic Building Trust, 19 9 2. )
The Taos Pueblo way of mixing is similar to the traditional
Devon way, except that the warm sunny summer weather allows
the people to do it barefooted in a dug-out shallow pit.
Athena and Bill Steen, while in Mexico working on the Save the
Children Foundation project, were taught by their Mexican col-
leagues how to mix the "no-effort way." Simply half fill the con-
tainer you are mixing in with water (most likely a wheelbarrow),
then use a shovel to sprinkle the dry earthen mix into the water in
the proportions you have derived from testing (or use pure clay).
Make sure the distribution is even and not too thick. If the mix is
not ready, alternate shovels full of the necessary clay, earth, and/or
sand. Once earth covers the top of the water, go and have a cup of
tea or a lunch break. Let it sit long enough for the soil-clay mixture
to absorb all the water. The speed of absorption depends on the
fineness of the clay-soil particles (for instance, whether it has been
sieved). After a few minutes, test the mix by sticking your finger
in. When ready, it will be smooth and creamy. If it is still lumpy and
hard, or partly dry, it needs to sit longer. If the soil has not been
BUI LDI NG WI TH CLAY
1 09
sieved, up to half an hour might be neces-
sary. When the mix is ready, work it thor-
oughly with your hands, stirring around
so that the sand, clay, and water are well
mixed into a soupy consistency. At this
stage, as much straw can be added as the
mix can take and still cohere, kneading
thoroughly with hands or with feet. For
foot mixing, dig a pit to use instead of a
wheelbarrow.
Another way of mixing, which I learned
at the Natural Building Colloquium, in-
volves placing the earth mix in a pile on
top of a plastic tarp. Water is added, and
two people hold the tarp at opposite ends,
leaning and pulling to each side, shifting
their grip on the tarp to roll the mixture
back and forth, and stopping from time to
time to add more water and straw. This
technique requires a substantial amount
of effort, but, as when mixing with feet,
your back remains straight, whereas mix-
ing by hand requires bending over a
wheelbarrow. Remember that the thor-
oughness of the mixing contributes to the
binding strength of the resulting mixture.
An endless variety of mixing methods is
constantly being developed and refined,
each one suiting different climates and in-
dividuals. Ianto Evans and Linda Smiley of
the Cob Cottage Company, who have de-
voted the past several years to the revival of
cob in the United States, believe that you
should always mix cob when happy. This
way the building is built with good as op-
posed to bad energy, enhancing its quality.
Mixing earth usually becomes a much-
loved activity, where not only the adults
but the children can all join in and have an
excuse to get muddy. And it is amazing to
see how quickly adults turn into children
when working with "mud," especially for
the first time. Therefore to replaster your
house once a year could turn into a huge
party and an excuse to enjoy yourselves
with your friends and relatives.
T H I N P A R T I T I O N S A N D
C E I L I N G P A N E L S
As an alternative to conventional gypsum
drywall, extensive research is underway to
produce structural members out of clay-
fiber composites. Prefabricated fiber com-
posite board is a form of industrial dry-
board developed in the past few years
(Andreson 1 9 9 7 ) . This board is made of
Mixing the clay.
110
Warni ng
Many conven-
tional insulation
materials create
environmental
problems as a
result of their
energy-intensive
and destructive
extraction and
manufacturing
processes. These
materials can also
cause health
problems during
installation or
even after,
because of
particle migra-
tion and off-
gassing.There are
now natural
insulation
materials for
almost any
situation.
fiber-coated, plant-fiber-reinforced clay,
manufactured by applying clay to burlap
fabric (jute net). For strength, two or more
layers of reed mats are inserted crosswise,
with alternating layers of clay paste. Fi-
nally, the surface of the board is covered in
burlap and transported to a drying station.
Tests with this kind of board have shown
excellent results with regard to fireproof,
soundproof, deformation, and diffusion
values. Such boards could be used, for ex-
ample, as a permanent form combined
with straw-clay or blown-in cellulose in-
sulation, or as ceiling panels (see Con-
struction Resources in the resources list).
They can be screwed, nailed, and sawed,
then plastered over as a finish. When a
smooth surface such as wood framing has
to be plastered, burlap can be placed over a
wet coat of base plaster and allowed to dry
before a final coat, or reed mats can be
used as lathe between sections of clay
board. And as noted in chapter 1, interior
partitions can be made with wattle and
daub or with the rammed straw technique
described below.
I N S U L A T I O N
Good insulation in a building can signifi-
cantly reduce the heating cost. Insulation
can be built into the walls, ceiling, roof,
and in some cooler climates the floor (see
the section on floors, page 115). It is a ma-
terial that will trap small pockets of air.
Natural alternatives to industrial fiberglass
include straw treated with potato starch or
borax for fireproofing or stuffed into
treated burlap bags, cotton, flax, or sheep's
wool. Cellulose insulation made out of re-
cycled paper ground up and treated with a
flame retardant can be blown into cavities
between rafters with a specially rented
machine to insulate the ceiling or roof, and
in timber frame construction, between
studs in the walls (it is also available in batt
form). Hemp cellulose (fireproofed with
mineral salts and called Canobite) can also
be purchased, either loosely packed in bags
or to be blown in. Wood-fiber boards can
also be used for thermal and acoustic insu-
lation (Tibbies 1997-98).
To increase insulation value in an
earthen mix, straw, wood fibers, cork, and
other air-trapping fibers can be used, ei-
ther added into the earthen mix or at-
tached in panels along the walls. Pumice,
perlite, and other minerals used for floors
and screeds can also be added as an aggre-
gate to increase the insulating value of in-
terior plaster and ovens. One of the best
insulating materials for corbeled dome
construction is pumice-filled bags (see the
profile of Kelly and Rosanna's house on
page 135), but this material occurs natu-
rally in very few parts of the world and is
costly to purchase and transport.
Earthbag domes in sunny climates do
not require insulation, if the design pro-
vides for passive solar heat in the winter,
and openings are placed in a way that they
do not allow direct sunlight into the house
in the summer. If the dome is lived in and
BUI LDI NG WI TH CLAY
111
heated regularly either by the sun or a
stove, the thermal mass of the earth will
retain heat in the winter and coolness in
the summer.
For earthbag domes built in cold cli-
mates, if desired the insulation can be in-
corporated in the floor, ceiling, and final
layers of the internal and external plaster,
which can be significantly thickened to
provide a more insulative finish using a
layer of straw-clay on the inside and paper-
crete outside.
Straw-Light Clay
As mentioned above, straw can be coated
with clay slip called straw-light clay and
used as insulation in many different ways:
stuffed between rafters as roof or ceiling
insulation, placed in the floor using the
rammed straw technique, or made into
lightweight blocks to construct relatively
thin but highly insulative walls.
To make light clay, pure clay is necessary
for maximum binding strength. The clay
has to be mixed with enough water to turn
it into a slurry called clay slip or liquid clay
(always adding the clay to the water, never
water to the clay). If the mix is lumpy or
contains stones, it could be passed through
a 1/8-inch screen. The consistency should
be such that when you dip the palm of
your hand in the mix no lines can be seen
on your hand. The purer the clay, the
thinner it can be diluted due to its greater
binding strength, thereby achieving a
lighter straw-clay mix.
To prepare straw-light clay, pour the
clay slip on top of a pile of straw, tossing it
like a salad with pitchforks. Coat every
single piece of straw completely with clay
slip. To test if it is coated enough, take a
bundle of the mix and squeeze itif it
sticks together, it is ready. If time allows, it
is then best left for a day or two under a
tarp to mature and improve.
Another application for light clay is the
technique of rammed straw, whereby the
mixture described above is used to con-
struct walls and partitions. After being
coated with clay slip, the straw-light clay is
lightly rammed between the form boards
(shuttering) with a 2 x 4 (or your feet) until
it is solid and not spongy. The forms can be
moved up to the next lift immediately after
completion of each particular section. To
preserve the insulation properties (that is,
trapped air in the straw), it is important
for the tamping not to be too hard.
An earthship (rammed
earth in tires) wrapped
by straw bale insulation.
112
Three
different
ways of
integrating
earthbag
and straw
bale wall
systems.
BUI LDI NG WI TH CLAY
113
Hybrid Earthbag and Straw Bale
Straw bales are among the best value for
natural insulation, but unfortunately they
take up a lot of space. They can be used as
floor or roof insulation on ladder trusses
or as insulation for living roofs. Bales can
also be used in conjunction with earthbag
walls either as internal supplementary in-
sulating walls, creating a three-foot-thick
wall, or as nonstructural infill in combina-
tion with load-bearing walls or piers, cre-
ating buildings that have the structural
stability and thermal mass of earth (on the
east and west side, for example) and the
insulation value of straw bales on the cold
north side.
Straw is an annually renewable re-
source, the waste product of a cereal grain
crop, and can be easily grown and har-
vested. Bales can also be made out of
tumbleweed, sudan grass, and ordinary
meadow hay, but straw is the best natural
insulator due to its hollow stems that trap
the air, and it is not attractive to vermin
since it lacks nutrients. The straw bale
technique represents an entirely distinct
construction system, which needs to be
Above: Building with rammed earth.
Left: A rammed straw wall.
Detail section through an earthbag wall with straw
bale wall for added insulation.
gravel trench
A house where two (east and west) earthbag walls are structural
and the straw bales are a nonstructural insulating wall on the
north side, with glazed frame construction on the south-facing
front for passive solar heating.
strings to tie
the bales are
fed through
tubes left in the
earthbag wall
earthbag wall carrizo or other
wooden poles
sandwiching the
walls
a pole tied to the
earthbag wall providing
air space (at intervals of
2 per bale)
straw bale tied to
earthbag wall
earthen plaster covering
the straw bales
earthbag footing for
the straw bale wall
string that
ties the straw
bales to the
earthbag
wall
114
understood as a system in itself before it
can be properly applied in combination
with earthbags, adobe, or cob. Straw bale
structures can be load bearing or non-
load-bearing. A number of good books are
available on straw bale construction (see
the bibliography).
I N T E R I O R D E T A I L I N G
Several earthbuilding techniques can be
used for sculpting furniture as well as for
construction of small structures and
houses. Earthbags, rubble, cob, adobe, the
different straw-clay mixes, and straw bales
can all be used to construct the main struc-
ture of sculpted furniture, sealed and
smoothed out with an earthen plaster,
then capped with lime, gypsum, or some
other clay paint finish for durability.
The materials used for creating furni-
ture can also be used for stoves and ovens
by adding less straw and more sand, per-
lite, or pumice to the mixture. These
earthen heaters can be sculpted with
niches, alcoves, and benches to suit the size
and shape of a house. By embedding a flue
in an earthen bench, you can make a warm
seating area.
For the interior partitions or even exte-
rior walls where the earth has insufficient
binding strength to hold nails carrying the
weight of fixtures, the installation of hang-
ing cabinets and other furnishings re-
quires a nailer board that can be installed
after the wall has dried. In preparation,
wooden stakes should be placed between
the rows of earthbags before tamping, or
embedded in the cob or adobe with a led-
ger board attached across two or more
stakes, which provide anchors for nailing.
Earth-plastered shelving being
constructed with straw-clay blocks
and carrizo decking.
BUI LDI NG WI TH CLAY
115
In addition to being used in wall construction, cob can be used to sculpt furniture
in a very freeform wayseating, desks, and shelves. Benches can be made of solid
cob with a flue from a woodstove coming through and warming them while the
stove is used, creating a "cozy" corner through the winter months.
existing wait
stabilized earthen plaster
slightly sloping to shed
water
cob
well-conditioned
gravel and rubble
Exterior cob bench.
Interior heated bench.
existing wall
earthen plaster
well-compacted rubble and
earth, or solid cob
possible flue from oven
to heat the bench
adobe or cob wall
to retain the
rubble
earthen plaster or sculpted
cob can also have flagstone
embedded in the surface and
can be stabilized with linseed
oil (in rainy climates covered with lime or lime-
stabilized earth),
stone or rubble
Exterior earthbag bench.
stone as a
border
between the
cob and the
existing wall to
protect the
wall from
moisture
well-tamped
earthbag
well-tamped
gravelbags
cob wall to retain the
gravel or rubble
well-compacted gravel
Then a cabinet or other fixture can be at-
tached with screws or nails to this ledger
board.
E A R T H E N F L O O R S
For centuries, earthen floors were used all
over the world. Until recently, they were
the standard floors throughout the south-
western United States, where they are cur-
rently being revived. In spite of the stereo-
type of "dirt floors," earthen floors need
not be dusty, fragile, or difficult to clean.
The right application of oil and wax makes
earthen floors waterproof and almost as
durable as concrete. Some of the earthen
floors I have seen have been walked on
with high heels, and can take the pressure
of furniture. There is no one correct way of
Exterior cob seating.
116
constructing these floors. The materials
used vary according to availability, but the
quality of the floor primarily depends on
the workmanship. It is possible to create
earthen floors that are durable and require
little maintenance, if certain basic prin-
ciples are understood. The method I
learned from Bill and Athena Steen of the
Canelo Project, who have produced an in-
troductory earthen floor booklet (see the
bibliography); therefore, I will only give an
outline of the construction method.
The floor should be poured during the
driest part of the year. It can take between
ten days and six weeks to thoroughly dry
out. The layers of an earthen floor are as
follows (make sure each layer is fairly level
to minimize your work on the final layer):
Layers of an Earthen Floor
Earthen floor layers with flagstone embedded into the top layer.
BUI LDI NG WI TH CLAY
1. Base: This layer should be either undis-
turbed soil, or at least a very well-com-
pacted surface, since it needs to be free of
all organic matter and unlikely to heave in
frost, so that no movement occurs.
2. Waterproofing: This layer is only neces-
sary in very damp areas that cannot be
properly drained. The waterproofing can
be natural clay such as bentonite (which
should be tested prior to construction) or
a synthetic damp-proof membrane.
3. Drainage: To stop any moisture from
rising, this is a layer of 6 to 12 inches (150 to
300 millimeters) of washed gravel or
course sand, tamped down well. If no
waterproofing membrane is used, the
gravel needs to be quite large to 1
inches (20 to 40 millimeters) in diam-
eterto prevent the rise of moisture.
4. Insulation: This layer should be 4 to 6
inches (100 to 150 millimeters) of straw-
light clay or pumice, perlite-clay, or bottles
embedded in sand, well tamped.
117
6. Finished floor: The top structural layer,
approximately 1 inch (25 millimeters) of
trowelled clay-earth mix. The clay-earth
mix should be comparable to a good
earthen plaster mix (see chapter 6), and
should be troweled in two half layers; the
top layer will need stabilizer. Other options
include 4 to 6 inches (100 to 150 millime-
ters) of well-tamped clay-sand-soil mix or
2 to 3 inches (50 to 75 millimeters) of clay-
soil mix with psyllium (the mucilaginous
powdered seed of the Plantago psyllium
plant, also used as a laxative). For natural
stabilizers, hardening agents such as lime,
blood, or wheat paste can be added (see the
discussion of stabilizers in chapter 6).
Floor, showing
alternative insulation
layer of bottles
embedded in sand.
5. Subfloor: The aim of this layer is to
achieve maximum compaction on top of
the insulation, in preparation for the fin-
ishing layers of earth. It should be com-
pacted silty or sandy soil, the same as the
base. This is the layer that can take radiant-
floor tubing. If a floor heating system is
used, the subfloor must be considerably
thicker to provide adequate thermal mass.
7. Sealant: Apply several layers of an oil-
solvent solution for added protection. Use
boiled linseed oil or other stand oil, as
these are oils that dry well, and which can
also be used for other earthen finishes. For
the solvent, the least expensive is turpen-
tine, but you may use anything from com-
mon mineral spirits to more-expensive
odorless turpentine or pure citrus oils.
118
Examples of an upper
floor with an earthen
floor finish.
finished floor layers
"evening out" layer of
clay with sand and
low-density of straw
willow, hazel, or
carrizo arches
finished floor layers
"evening out" layer
reed or straw-clay
rolls
floor joist
finished floor layers
"evening out" layer
layers of carrizo
floor joist
If you wish to consider construction of
an earthen floor for an upper story, a
straw-clay mixture can be used to fill in the
space between the ceiling joists, as shown
above. Then the layers of earth can be
poured upon that base as described below.
Construction
Use screed boards as wide as the depth of
the layered floor, initially placing them flat
near the wall where you will start pouring.
Remember to start at the farthest corner,
working your way out toward the door.
With an accurate level, keep checking that
each board is level as you use them as
screeds. Pour the mix between them, and
lay a straight board across the top of them.
Remove the board farthest from you, and
fill in the void where the board had been
with more mixture. Reposition the first
board, level it, and keep going. It is best if
your mixture is not too wet and keeps its
shape when each board is removed. For the
final layer, hammer in nails so their heads
are level with the height of the finished
floor. Use them for leveling the board, and
pull them out as you go along.
Screeding.
Here are some other ideas for natural
floors. Lay a gridwork of equal-sized 2 x 4
timbers before pouring the final layers,
then fill the spaces between them one by
one, leveling at the same time. The timbers
can be permanent or else removable when
the mixture is "leather-hard," and the
voids can then be grouted with a different-
colored mix. An alternative to a poured
adobe floor could be sundried adobe
bricks set in place like tiles with a mud-
sand mortar. Fired brick, tile, or flagstones
BUI LDI NG WI TH CLAY
can also be set with adobe mortar for ar-
eas of the house that get wet frequently,
such as the kitchen, bathroom, mud
room, or entrance hall.
Sealants, Maintenance, and Repair
The top layer should be completely dry
before applying the sealant. To be most ef-
fective, the oil-solvent solution should be
heated, taking care not to reach the point
where it begins to smoke. Warming en-
courages deeper penetration of the oil
into the floor. If the ambient temperature
of the room with the floor is warm, the
sealant will be better absorbed. Apply
with a brush, and remove the excess. Each
coat should be applied only thick enough
that it does not begin to puddle, for if al-
lowed to puddle it may form a skin on the
surface, which will be prone to cracking.
Note that both oils and solvents are very
flammable and should be treated with
caution when heating. Any brushes or
rags used during application should be
stored carefully in closed containers to
prevent spontaneous combustion.
It is better to apply the oil in a stronger
concentration in the initial coats, gradu-
ally reducing the proportion of oil to sol-
vents in the following coats. The earthen
floor is less porous with each subsequent
coat of sealant, but will accept full-
strength oil at the beginning.
According to the Steens' Earthen Floors
booklet, the sealant coats can be diluted as
follows:
Beeswax for Floors
In a double-boiler wi th water in the
bottom section, melt 24 percent beeswax
and 6 percent carnauba wax at 140 to 158
degrees Fahrenheit (60 to 70 degrees
Celsius).
Add 30 percent balsam turpentine from
spruce or larch and 40 percent boiled
linseed oil.
Increase linseed oil and reduce beeswax
to make a softer mix. You may use citrus oil
instead of pine turpentine.
coat 1apply full-strength oil
coat 2dilute the oil with 25%
solvent
coat 3dilute with 50% solvent
coat 4dilute with 75% solvent
Each coat should be applied only after
the previous one is dry. The floor should
only need four coats to be sealed. For addi-
tional sheen and durability, another coat
can be applied periodically. The frequency
of maintenance will depend on the wear
the floor receives, but for an average floor
6- to 12-month intervals is sufficient. If
sheen is not important, the floor does not
have to be recoated for many years.
If you want the floor to be not just water
resistant but waterproof, after the floor has
dried from the last application of oil, apply
a coat of wax. Make a paste by melting 1
119
part beeswax with 2 parts boiled linseed
oil. While the paste is still warm, rub it into
the floor with a clean rag. The wax layer
will rub off over time, so reapply it every
few months or once a year.
If cracks or other wear-and-tear begin
to show on the floor surface, it is good to
patch these places fairly quickly to avoid
them growing larger in size. When con-
structing the floor, save some of the mix
for later repairs, as it will be almost impos-
sible to match the color later. After clear-
ing the area that needs repair and crackup
off all loose material, add some water to
the dry mixture and mix thoroughly. Then
wet the damaged area, fill it in with the
mix, and reseal the surface as described
above, with four layers of sealant.
E L E C T R I C I T Y A N D P L U M B I N G
For electrical and plumbing utilities, it is
safest to place all the service ducts that en-
ter and leave the house below ground level
going through the foundations, to prevent
freezing and to minimize damage if a pipe
does fracture. This can be planned into the
design ahead of time, enabling the inser-
tion of plastic sleeves through the founda-
tion and floor where necessary during
construction.
A plumbing chase can also be created in
partition walls and under the floor. Non-
pressurized drainpipes are safe to route
through earthbag walls and can go directly
out to a separate graywater system for each
sink. If pipes must be run through earth-
bag walls, they should be encased in a
larger-diameter sleeve that is sloped down
to the outside. That way if the inner pipe
gets a leak, the outer sleeve will direct the
water outside the house where it can be
seen, instead of soaking the inside of the
wall without anyone knowing.
Electrical wiring and J boxes can be
placed as the rows of the earthbags go up,
or can be added in the grooves between
courses before plastering. Cut 12-inch-
long (130 centimeter) pointed stakes out
of 2 x 4s to anchor the electrical boxes in
the earthbag walls. After making a notch
for the box to recess into the earthbag sur-
face, drive the stake in. Even easier, place
the stake in the wall between courses dur-
ing the laying of the bags. You can screw
the box to the end of the stake and place
the wires between the courses of bag. Use
heavy-gauge, U-shaped wire pins to hold
the wiring in the grooves. If you are using
cement plaster internally, you may want to
Electrical box fixed to wooden stake for anchoring in
earthbag wall.
BUI LDI NG WI TH CLAY
121
cover the wires with a thin strip of metal or
plastic to keep the stucco from contacting
the wires. Wiring that is plastered into a
wall is difficult to modify, so test your wir-
ing fully before plastering; or route your
wiring in conduit, which can be made out
of plastic tubing or discarded garden hose,
either set into grooves between courses or
exposed on the wall surface for future ac-
cessibility and convenient servicing. The
other option is to consolidate all the wir-
ing on the interior partitions (if they ex-
ist), in the ceiling, or in raised floors with
floor outlets.
1 2 0
8
S
ince the inception of this book, numerous earthbag projects
have been built. This chapter offers a survey of the earliest
and therefore some of the most adventurous. These include
examples of the Hart's very experimental freestyle dwelling; the
amazing demonstration of courage by Shirley Tassencourt, then in
her late sixties; and Kaki Hunter and Doni Kiffmeyer's advance-
ment of the earthbag technique to true perfection. Each of these
projects yields tremendous inspiration and many lessons.
S H I R L E Y T A S S E N C O U R T ' S D O M E S , A R I Z O N A
To my knowledge, the first earthbag domes to be actually inhab-
ited were built by Shirley Tassencourt with help from friends and
relatives, including her grandson Dominic Howes. Shirley chose
the earthbag technology because of its "magic" and her limited
finances. As she is an artist who often sculpts with clay, earth
seemed like a familiar medium.
Between 1995 and 1997, Shirley built three earthbag structures:
first, a meditation dome, "Domosophia"; next, a main house
dome; then, a rectangular-shaped library with a conventional roof.
The soil used to fill the bags was brought from nearby.
The Meditation Dome
The meditation dome has an external diameter of 15 feet (4.5
meters)with 1-foot-wide (45 centimeter) walls sitting on bed-
rock, a cement-stabilized row of earthbags below the rafters of the
mezzanine level, and a reinforced concrete bond beam pinned to
the wall, serving as the compression ring for the opening. Exte-
rior and interior plasters are cement stucco. The upper level was
T H E E A R T H B A G A D V E N T U R E
123
124
T HE EARTHBAG ADVENTURE
125
Section of the
Meditation dome
Above: The first lived-in
earthbag dome built in
Arizona by Shirley
Tassencourt with her
grandson Dominic
Howes.
designed to contain a small studio space
with a 360-degree view of the surrounding
land.
Here's how Shirley tells the story: "At the
age of fifty-two, as a first-time contractor/
owner-builder of a 1,500-square-foot salt-
box on Martha's Vineyard, I thought I had
just made it under the doddering line. But
as a retired art teacher and potter/sculptor,
I had another go at it in Arizona's high
desert. Then as I sat in the dome at Cal-
Earth listening to Nader Khalili, I was ob-
sessed with wanting to be in such a cen-
tered, dynamic, revolving space. Being old
enough (sixty-nine) not to be hampered
by reality, I went home and started the next
day on the Meditation Dome. Some ad-
venture, oh my! Lady luck hovered over the
total projectundertaken by me in my
late sixties, my nineteen-year-old grand-
son Dominic Howes, and a fun young married couple, Luther and
Cindy McCurtis. We figured it out as we went along. With four of
us working for five hours a day in the desert heat using small bags,
in three months we finished the essential dome, Domosophia. A
carpentry crew made the 7-foot-diameter clerestory (with its 360-
degree view); they brought the spidery structure out in a truck and
plopped it on top. We covered it with chicken wire, tarpaper, and
stucco, and voila-I had my heart's desire."
Above: The skylight being constructed on top of the
compression ring.
Above left: The cost of materials for the main dome
structure and finishes (without utilities) was about
$6,000, primarily for cement and specially made
windows, doors, and skylight.
Insert: The library was built under a pole supported
roof, which provided a cover for shade. Earthbags
were used as infill, as in a post-and-beam
construction.
The Main House Dome
The second-story floor rests on a concrete bond beam, and the
mezzanine level has a sky view. No other foundation was needed,
as the ground is bedrock. The earth was dug out 6 inches (150 mil-
limeters), and a poured concrete slab finished with tiles. External
and internal plasters are cement stucco without lath; the uneven
surface of bags provides enough reinforcement and key-in points.
Again, here is Shirley's own account: "Emboldened by our suc-
cess, in 1995 in a hot September desert, we started on the second,
larger dome, this time built with an engineer's approval. It took us
five months and 5,000 small sand bags. This dome has a 25-foot
footprint, with a double (42-inch-thick) earthbag wall 9 feet up to
the base of the mezzanine level with earth rammed in the cavity,
which is sealed with a concrete bond beam. The outer wall acts as
a huge buttress, and could have been considerably smaller, but
there was little precedent for this kind of construction using small
bags. We hand-lifted 25,000 pounds of earth on straw-bale scaf-
folding for our 20-foot-high building, crowned with a 5-foot-high,
7-foot-diameter plexiglass skylight. Skylights offer gifts of sky and
landscape unusual to dome construction. Twelve-inch PVC tubes
through the second-floor walls plus a window-door to the balcony
allow inexpensive fenestration and continuous air flow from two
doors below, which are open all summer. [Author's note: In Ari-
zona, this skylight has to be covered in the summer due to the in-
tensity of the sun, and in winter it causes considerable heat loss.
The skylight should be off-center, angled south.]
"My grandson was an apprentice for the first dome, foreman on
the second dome, and a contractor on our neighbor Allegra's
house (see page 127). Dominic went on to build a large, rectangular
earthbag- and roof-truss hybrid structure in Wisconsin. Here in
Arizona, I and two other elder women have thirty acres off-the-
grid. We embrace Permaculture, gardening till the grasshopper
plague arrives in July. We do ceremonies, and connect deeply with
the land through our fifteen-acre natural medicine wheel (made
with big boulders marking the cardinal directions on a circle). We
want to encourage ot her s. . . . If we can do this, anyone can!"
T HE EARTHBAG ADVENTURE
127
A L L E G R A A H L Q U I S T ' S H O U S E ,
A R I Z O N A
This house is situated on the land shared
with Shirley Tassencourt in Arizona. It was
built by Dominic Howes, finished in 1997.
It is an example of mixing alternative tech-
nology with conventional construction.
Buttressed earthbag walls stand on a con-
crete foundation, and are tied together
with a bond beam supporting a timber-
trussed roof. Allegra is very content with
her 625-square-foot house. The house
took four months to build and cost 40,000
dollars, the biggest expenses being a con-
ventional roof, foam insulation, concrete
foundation, windows, doors, cement
stucco, and labor, which was about one-
quarter of the final cost. The floor is brick
on sand with floor-heating tubing in the
sand layer. The south-facing windows pro-
vide passive solar heating; in fact, the in-
floor heating system (regulated by a ther-
mostat) has only been used six times in the
past three years in spite of cold winters.
Above: Allegra's square
house.
Left: Sketch plan of the
house.
timber truss
timber wall plate for the truss to sit on
concrete bond beam with contin-
uous reinforcement, pinned to the
earthbags at intervals
earthbag wall with two strands of
4-point barbed wire between
courses
2" (50 mm) of styrofoam insulation
chicken wire to enable the external
plaster to stick
concrete footing
Section showing wall-to-roof junction.
Section and plan of Shirley Tassencourt's Main House
dome. Note the double earthbag wall up to the
mezzanine level.
126
H O U S E B U I L T B Y D O M I N I C H O W E S , W I S C O N S I N
The house is situated in an extreme cli-
mate where the temperatures range from
as low as -40 degrees Fahrenheit in the
winter up to the high 80s in the summer,
with heavy rainfall through the summer
months. Designed by the client, it has two
stories where the second is of conventional
construction, with high windows for pas-
sive solar access.
This house was built by Dominic
Howes almost directly after construction
of Allegra Ahlquist's house (page 127);
therefore, the treatment of the earthbag
wall is carried out in a similar manner. It is
almost entirely a conventional house with
standard timber-frame construction and
artificial foam insulation, but instead of
using brick or concrete for the structural
walls it uses the earthbags filled with the
local earth.
The earthbag part of the house took
three weeks to build. The floor area of the
house including the first floor is approxi-
mately 1,500 square feet.
Structural section through the south wall. Detail section through the south wall. Above:The finished
house.
The house under
construction.
128
T HE EARTHBAG ADVENTURE 129
130
S U E V A U G H A N ' S H O U S E , C O L O R A D O
Sue Vaughan wanted a very small, round house, so
with the advice of Kelly Hart, she and two helpers
built this 14-foot ( 4. 2 meters) diameter, shallow
dome with a sleeping loft made of scoria-filled
bags. A concrete bond beam at the height of the
door lintel supports a geodesic structure form-
ing the upper part of the dome.
Section of Sue Vaughan's dome.
T HE EARTHBAG ADVENTURE
131
C A R O L E S C O T T A N D S T E V E K E M B L E ' S H O U S E , T H E B A H A M A S
Here is a house designed and built in the Bahamas by Carol Escott and Steve Kemble of
Sustainable Systems Support. The first phase of the construction, which consisted of the
structural earthbag walls, was constructed with the expert help of Kaki Hunter and Doni
Kiffmeyer, who have developed site-built hand tools and a process for building that sim-
plified and "neatened" this very labor-intensive construction method. Kaki and Doni's
Honey House is described on page 140.
This is a hybrid design where the first story is constructed out of bags filled with native
soil, upon which sits a second floor and roof constructed out of conventional timber
frame. The second-floor joists are fixed to a reinforced concrete bond beam on top of the
earthbag wall.
The house was built on a small island very close to the beach. The fill for the earthbags
was locally available sand dredged from the sea, which was very fine and contained a high
proportion of crushed coral, so it was very easy to compact. When slightly moistened and
tamped, the bags turned to solid blocks.
The finished house.
Preparing the
foundation.
Sue Vaughan in front of
her scoria-filled earth-
bag dome, which is
covered with standard
cement stucco.
Above:The upper section
of the dome from the
inside, showing the
geodesic structure.
132
Since the ground around the house was
sand, drainage was not a problem; there-
fore, the foundation was very shallow with
no gravel trench below, simply one row of
sand-filled bags below ground level.
In an article in Earth Quarterly (see the
bibliography), Carol and Steve describe
the premise of their design process: "Faced
with the challenge of building on a remote
island in the Bahamas, we realized t hat . . .
current construction trends in this part of
the world rely on the importation of al-
most all building materials in even the re-
motest of locations. In keeping with our
work in the States, we want ed. . . to use this
project as a demonstration of appropriate
earth building techniques . . . in hope of
influencing a shift i n. . . building/develop-
ment needs."
Carol and Steve faced serious difficul-
ties: The Bahamas are subject to devastat-
ing hurricanes each summer and fall.
There are voracious termites, making any
wood product is subject to attack. It also
rains frequently and things may stay moist
for weeks. The intense summer sun can
cause even pressure-treated wood, if ex-
posed, to deteriorate in as little time as five
years.
According to Carol and Steve, the Baha-
mas have developed very little industry
except for tourism, so most building ma-
terials are imported from the United
States. In terms of native resources, the
majority of vegetation is low bushes, with
trees for lumber being virtually nonexist-
ent. The most abundant and easily gath-
ered natural building resource is sand.
Carol and Steve realized that where dredg-
ing had occurred for a marina there were
piles of sand mixed with crushed coral,
available free for the taking. When slightly
dampened and well tamped, the lime in
the coral acts as a natural binder with the
sand, which sets into a hard block.
Since the climate is subtropical, hot and
humid, ocean breezes are needed for com-
fort. Most people clear-cut the bush to al-
low the breeze to blow through and to
eliminate hiding places for the mosqui-
toes, but Carol and Steve let the foliage
grow around their site in order to provide
overstory protection for new plantings,
shade to help with moisture retention, and
wall plate anchor bolted
to bond beam
reinforced concrete bond beam
reinforcement rod pins
four-point barbed wire
straps over the bond beam
reinforcement rods
well-compacted bags filled with
local sand
First floor under construction.
compacted sand
Plan of ground floor.
133
line of roof overhang
to encourage biodiversity and habitat for
beneficial wildlife, as well as for privacy
around the house.
To collect the breezes, Steve designed
the home to be two stories with an at-
tached deck on the second level. The roof
is hipped to shed heavy hurricane winds.
The first level has walls made of sand- and
crushed-coral-filled polypropylene bags
along the perimeter, with a peaked, 8 -
point-arch opening in each of the six sides.
These arch openings have been left open
for breezes, and the covered lower level is
used for utility, storage, and a workshop.
At the center of the lower level is a 3,000-
gallon, concrete-block rainwater cistern,
which also serves as a load-bearing sup-
port for the second level.
These earthbag walls used misprinted
50-pound rice sacks for the first four feet,
resulting in a 20-inch-wide (50-centime-
ter) wall. The next four feet were built with
continuous tubing, resulting in a 14-inch-
wide (35 centimeter) wall. Since the earth-
bag walls were made very smooth with a
high-precision finish, there was no rough
texture to permit the stucco to be effec-
tively keyed into the wall surface, which to
reinforce the cement render was therefore
covered with a layer of chicken wire, se-
cured to the walls with galvanized tie-
wires laid between bag courses as the walls
were built. The bond beam was strapped
to the earthbag wall using both the chicken
wire and the poly strapping, which was
ratchet tightened before stuccoing.
Plan of ground floor, used as utility area and workshop.
T HE EARTHBAG ADVENTURE
135
The 512 square feet ( 40 square meters)
of the ground floor, earthbag stage of the
house took three months to build, requir-
ing 500 bags and a 1,400-foot roll of
polypropylene tubing.
Carol and Steve conclude: "After the
completion of Phase 1 (the earthbag wall
base) we were very pleased with the results
of the project. The islanders have accepted
it, stating that it looks like the old 'rubble
stone' ruins around the island. It feels very
st ur dy. . . enough to take the worst hurri-
cane, relentless sun, and regular wind-
blown rains. It cost a fraction of the money
any other option would have, to get to this
point. Although it took a lot of manual la-
bor, it is a doable method with only mini-
mal hand tools, and we had fun coordinat-
ing our team work into a smooth process.
The three young men we trained are look-
ing at building houses for themselves us-
ing this method, and are even discussing
becoming contractors for other people."
Top: Ground floor during construction.
Bottom: Earthbag stairs.
KELLY AND ROSANA HART' S HOUS E , COLORADO
This house, designed and built by Kelly
and Rosanna Hart of Hartworks, Inc., is in
a small town at 8 , 000 feet in the foothills of
the Sangre de Cristo Mountains of south-
ern Colorado. Several interesting features
distinguish the main dome of this house.
The walls are constructed of bags that
contain scoria, a very porous, pumicelike
volcanic stone. It is locally available, and
like pumice, it has many air pockets and so
is very light. Due to its porosity, scoria is a
good insulator and also provides thermal
mass, so the house can absorb the sun's
heat and retain it throughout the night.
Kelly estimates that the finished scoria bag
wall covered with papercrete inside and
out will have an R-value as high as 4 0,
which is higher than building codes re-
quire. Scoria is also light and fast to work
with.
Another unusual aspect of this house is
that although the main structural form
appears to be a dome, it is not a self-sup-
porting corbeled dome. For a true cor-
beled dome, the design needs to be circular
in order to create an evenly curved wall
upon which the vertical and horizontal
forces are equal everywhere. In this case,
the plan is oval, so timber poles have been
used as a type of pitched-roof teepee ar-
Roof structure to
support the scoria-
filled bags.
134
136
rangement, insulated with scoria-filled
bags partially supported by the poles.
This dome is also covered with a differ-
ent type of plaster, which is water resistant
and insulative: a mixture of paper and ce-
ment or lime, or a combination of the two,
often called "papercrete" or fibrous cement.
The house is a hybrid, a juxtaposition of
different materials, as well as a network of
interconnecting structures allowing the
area of the house to be quite large without
using one single dome.
Kelly Hart describes part of the con-
struction process: "The sloping site was
leveled and dug down about a foot below
the eventual floor level, which was 5 feet
below ground level. Then 6 to 8 inches of
loose scoria was put over the entire build-
ing area to serve as insulation and good
drainage. There is no other foundation or
drainage, since the soil is pure, fine sand.
We tried using the on-site dry sand to fill
our polypropylene bags (misprinted rice
bags), but soon discovered that at a certain
point after about five feet of stacking, the
bags would not hold their shape and with-
out buttressing the wall would collapse.
[Author's note: When building with very
sandy soils, which consist of round par-
ticles of sand, a test structure should be
built prior to construction of the main
house, with bags not less than 20 inches
T HE EARTHBAG ADVENTURE
137
(500 millimeters) wide, making sure the sand is damp when filling
the bags, well tamped and buttressed.] So we switched to scoria,
which is a much lighter material and will pack into a tight, stable
wall. Because of the lightness of the scoria, in addition to the usual
four-point barbed wire running between each course of bags, we
tied the bags to each other with poly baling twine [see photo on
page 54], which provides a matrix of fabric across the entire wall to
resist fragmenting. It also gives the finish plaster something to
grab on to (especially important on interior walls, where in domes
you are working against gravity).
"We used individual bags as building blocks, rather than using
long tubes of material, because the small bags are easy for one per-
son to carry, and when we tried putting the scoria in long tubes,
With an old woodstove in the foreground, the dining area under the loft can be
seen beyond. Flagstones are set in adobe in the foyer. Beyond the table is a
windowseat constructed with earthbags.
Plan of ground floor.
138
Kelly applying
papercrete to the
outside of the dome.
This doorway has a
span of 6 feet made
possible using the
double-bag, cross-
hatch method of scoria
arch.
Kelly explains, "With the pantry dome open, you can
see how the bags are stacked, those long rafters
helping to support the bags. Because of the
relatively shallow pitch, bermed with earth on the
outside, and the considerable weight it would bear, I
decided to use logs. Before the pantry was backfilled
with sand, I put on two layers of 6-mil plastic
sheeting. The dome has not leaked and stays around
40 to 50 degrees Fahrenheit."
T HE EARTHBAG ADVENTURE
139
there was a tendency for the whole thing to roll off the wall.
[Author's note: This was due to the fact that the tube was narrow
and scoria cannot be made compact in the same way that slightly
damp earth or sand can. Therefore it may be advisable not to fill
the tube completely but loosely, to allow for tamping. Also, always
carry the fill to the bag, eliminating the need to lift.] With the in-
dividual bags, the bottom seam provides a distinct flat orientation
that resists rolling.
"Bags were stacked over a wooden form for the arched door-
ways. We used a plastic pipe to make air vents. Many of the win-
dows were created using old wagon wheels or culvert couplers to
hold the circular shape, and since most of the windows are not
operable, the glass used was often unclaimed or cut to the wrong
size; these thermal panes can be found cheaply at glass shops. They
were imbedded directly in the papercrete (which is so dimension-
ally stable it will not break the glass), and a second, final coat of
papercrete with sand was applied to the outside, overlapping the
glass.
"The space connecting the two domes is framed with wood on
the south side, while the north side is an insulating scoria-bag wall
in the shape of a semicircle. Because of the expanse of glass in this
greenhouse section, and the need for a flat place to mount the solar
water panels and PV modules, I chose to use conventional wood
framing on the south. The north side of the house is bermed with
about four feet of earth, and a mound of earth covers the pantry in
the north.
"The final layer on top of the papercrete is lime-silica, sand, and
white Portland cement plaster.
"Because of the elliptical shape, this dome is not as inherently
stable as it would be if it were circular, which is why I used the
timber pole. The forces are not uniform, so I had to struggle to
keep the shape I wanted. I would not recommend that anyone re-
peat this experiment, though I do love the shape and feeling as it
has turned out."
Kelly has made a video of this construction process (see the re-
sources list).
Unbuttressed arch.To create an arch spanning more
than 3 feet using lightweight scoria bags, Kelly
devised the crosshatched, double-bag arch system
shown here.
The Honey House with
sculpted gutters and
grass seeded in the
final layer of earthen
plaster.
K A K I H U N T E R A N D D O N I K I F F M E Y E R ' S H O N E Y H O U S E , U T A H
This house was designed and built in
Moab, Utah, by Kaki Hunter and Doni
Kiffmeyer of the pioneering firm OK OK
OK Productions, who have elevated earth-
bag construction to a precision craft. The
structure is a corbeled earthbag dome with
a 12-foot (3.6 meter) interior diameter.
Forty tons of earth were needed to fill the
bags, and 9 more tons were used for
sculpted adobe and for a "living thatch"
roof. The gutter system is sculpted adobe,
which steers the water around windows,
down buttresses, and away from the foun-
dation.
No cement was used in this structure!
The bags used were small "misprint"
bags of two sizes: 17 inches wide by 30
inches long and 22 inches wide by 36
inches long. The fill material used was "re-
ject" sand from a local gravel yard. This
had the ideal ratio of 25 percent clay to 75
percent sand for rammed earth construc-
tion. The time taken for filling and tamp-
ing the bags averaged four of the smaller
T HE EARTHBAG ADVENTURE
First floor under construction.
The interior has a sunken floor, 2 feet
(60 centimeters) deep. The earthbag wall
starts at this level; there is no concrete
foundation. Plastic bags were wrapped
around the exterior of bags below grade
for waterproofing from ground moisture,
then backfilled with gravel and earth. The
interior walls are earth plastered with local
white clay and milk-based alis paint. The
earthen floor is poured adobe over 4
inches (100 millimeters) of gravel and
stone with mud mortar, sealed with a
natural, oil-based floor finish.
Except for utilities, windows, and
doors, the cost of this house was $1,020,
which was the cost of the bags (a quarter of
the final cost, including delivery), home-
made tools, plywood arch forms (which
are reusable), chicken wire, backhoe
rental, twenty bales of straw for the
earthen plaster, two rolls of barbed wire,
and the 40 tons of sand, delivered.
In their manual Earthbag Construction
(see the bibliography), Kaki and Doni have
described their method this way, "We have
adopted the FQSS stamp approvalFun,
Quick, Simple, and Solid. By following this
criterion, we have made the ease of the con-
struction process our priority. As long as the
work is Fun and Simple, it goes Quickly
and the results are Solid. When the work
becomes in any way awkward, FQSS de-
teriorates into Frustrating, Quarrelsome,
Slow, and Stupid, prompting us to stop,
change tactics, or blow the whole thing off
and have lunch (returning refreshed often
spontaneously restores FQSS approval)."
bags per person per hour, so a team of four
averaged sixteen bags per hour, and about
ninety-six bags in a 6-hour day. The
Honey House is made of eight hundred
bags overall. The whole structure took just
nineteen days to complete.
The earthen plaster was made with 7
tons of cob, which took seven days to apply
all the way up to the roof, which has a 6-
inch base for a "live cob thatch roof," where
living grass roots were mixed into the final
layer of roof plaster.
140
141
T H E L O D G E " N J A Y A , " M A L A W I
In structures like the bathing room in the backpackers' lodge "Njaya" in Malawi, in southeast
Africa, Adrian Bunting experimented with the sandbag technology prior to constructing
a larger sandbag projectan eco-lodge in southern Tanzania. As Adrian explains, "I was
trying to get the hang of the sandbag technology based on a couple of photos on the Web.
The beach in Tanzania is as remote as you can probably get, so the plan was to build as
much as possible with the available materials, basically sand and coconut trees. In Africa,
concrete is what everybody wants to build with, but a lot of this is done with lime obtained
from live coral reefs, sustaining huge damage. It's also very expensive. I was sent to Malawi to
see if the sandbag technology was a viable option for constructing chalets in Tanzania. As
far as I could see, it was worth trying if only to achieve the thermal insulation these build-
ings provide, and also the ease of sealing against mosquitoes, since any timber building is
impossible to make bug-free."
The construction procedure used in Malawi is very different from the method de-
scribed in this book. As Adrian explains, "The bags are filled with pure dry lake sand, of a
granite type. There is no barbed wire, and I did find the bags slipped during construction
so the roof has reinforcement bars bent and used as a permanent form. The corridor is just
stacked in an arch.
"You might be interested in a conversation I had with the builder when we started the
roof. He was shaking his head, so I asked him why. He replied that this wasn't a roof. I asked
him why, and he replied, 'A roof is made of tin.' I
said, but tin is noisy when it rains, it
heats up quickly in the sun, and
when it's old mosquitoes get
in. 'It is still a roof,' he re-
plied. But this is ten times
cheaper, I pointed out.
'I see,' he sai d. . . . "
bent reinforcement rods (rebar)
forming a dome shape
earthbags stacked flat
without barbed wire
The permanent, dome-
shaped structure used
to support the
sandbags.
T HE EARTHBAG ADVENTURE
143
T H E N E W H O U S E O F T H E Y A Q U I S , M E X I C O
The indigenous Yaqui community of
Pueblo de Sarmiento is located on the out-
skirts of the city of Hermosillo, capital of
the Mexican state of Sonora, which bor-
ders the United States. Mexico's govern-
ment gave a ten-acre parcel of undevel-
oped land to the Yaquis of Hermosillo in
1995. This land is a desert at the bottom of
the surrounding hills.
Giovani Panza, of the organization
Itom Yoemia Vetchivo, whose mission is to
find funding for projects that improve the
Yaqui community's living conditions, be-
came acquainted with Pueblo de Sarmi-
ento through a conference of indigenous
peoples of the Mexico-U.S. border, which
was held in Hermosillo. In the spring of
1997, Itom Yoemia Vetchivo received a
grant of four thousand dollars to build the
Yaqui community a prototype low-cost
shelter, and they approached Cal-Earth
for help. With two volunteers experienced
in conventional construction who were
carrying out apprenticeships at Cal-Earth,
I offered to coordinate this project, which
was organized as a three-week volunteer
project.
The people of Pueblo de Sarmiento
usually build their own homes out of
whatever is on hand: cardboard, corru-
gated asphalt sheeting, and small pieces of
found timber. These structures need to be
rebuilt after the seasonal hard rains. They
had one source of fresh water coming into
the village, and no sanitation facilities
apart from an outhouse. In spite of the low
standard of living, we remarked upon a
sense of cheerfulness all around.
Taking stock of the materials available
on-site, we saw that one of the
few resources that was abun-
dant was earthvery sandy
with hardly any clayso the
earthbag technology would be
very appropriate.
The house was to be a Nader
Khalili-designed, low-cost pro-
totype, the "three-vault house,"
which utilizes a simple design
based on the repetition of single
arched units, simplifying con-
struction. Khalili's arrangement
of vaults eliminates the need for
corridors, and additional vaults
can be added later easily. Resi-
dents have a view through the
depth of two vaults at one time,
increasing the sense of interior
spaciousness, and variety can be
introduced through placement
of windows and other elements
such as niches and alcoves. A
wind catcher faces prevailing summer
breezes to direct air into the house for
cooling. In addition, the vaulted curve of
the roof creates shaded zones of cooler air,
while the sun's path overhead encourages
air movement inside house by gradually
Top: A house con-
structed of corrugated
asphalt, which becomes
unbearably hot in the
Mexican sun.
Above: Prototype of the
three-vault house.
142
1 44
shifting the shaded zone up and over the
vault.
Contrary to my intentions, the people
of Sarmiento were asked to prepare a con-
crete foundation prior to our arrival,
which was the first of many unnecessary
measures in this project. Due to this extra
work, time was lost.
A team of fifteen Yaqui workers had as-
sembled for the project. Some were from
this community, and others came from the
village of Ciudad Obregon, farther south.
They were all to receive standard Mexican
wages, which to us meant that their motive
for working hard would not be primarily
educational. Yet with all this available la-
bor, I could not have foreseen what could
go wrong.
Once the concrete of the footings had
cured, the work began. At first, earthbag
construction seemed very strange to the
Yaquis, and reluctantly, but with great
merriment, they embarked on this adven-
ture with space-age technology. Their first
day of laying bags was very slow, but soon
they gained experience and speed. The
Cal-Earth advisers, who were not them-
selves accustomed to alternative construc-
tion, had insisted on putting 12 percent ce-
ment into the earthen fill, thereby treating
the bags as concrete forms instead of
rammed earth. In six days, the laying of the
earthbags was complete and the structure
was ready for the vault construction. Over
the whole week, the speed of the bag laying
averaged 23 feet per hour per team, with
three people in each team.
At this stage, we faced a huge di-
lemmawhether to build some kind of
timber formwork (the cost of which would
come to more than what was budgeted for
the whole house), or instead to try and
devise a way of constructing the vault us-
ing permanent, built-in formwork. "What
T HE EARTHBAG ADVENTURE 145
is the point of building a house without
any wood if you are going to use vast
amounts of wood for the formwork?" was
the commonsense question. A way of
building a vault using reinforcement rods,
expanded metal mesh, and rigid foam in-
sulation was devised. "What happened to
the idea of natural, alternative construc-
tion?" was my constant question.
Unfortunately, the concept of empow-
erment through use of the simplest tech-
niques and the most available materials
was almost lost, because the local people
were unable to build more of these build-
ings due to the vast cost of the materials
used in the prototype. So what went
wrong? Why did the project's cost escalate
from the four thousand budgeted to ten
thousand dollars? The most expensive
material costs of the project were: cement,
for foundations, walls, and roof; metal, for
the roof structure; and rigid foam, for the
insulation. There were numerous possible
alternatives. For instance, the foundations
could have been inexpensive gravel- or
rubble-filled trenches; or two stabilized
earthbag rows laid directly on undisturbed
ground, since this is not an earthquake
area; or two courses of bags filled with
gravel laid on undisturbed ground (see the
descriptions of earthbag foundations in
chapter 3) .
There was no need to put any cement in
the fill for the walls. The earthbag technol-
ogy has been specifically developed for
building in areas with no clay or wood, and
using unstabilized earth would have been
entirely practical at Sarmiento. For the
roof structure, it would have been better to
use the locally grown, bamboo-like carrizo
reed for vaults (see page 67 ), or corrugated
metal sheeting, which is cheap and easily
T HE EARTHBAG ADVENTURE
available. As for insulation, a straw-clay
mix would have been preferable to expen-
sive rigid foam (see the discussion of roofs
in chapter 5) .
This project underscored the truth that
a thorough understanding of any building
technique is necessary to avoid unneces-
sary cost and complexity. Moreover, when
working with builders who speak different
languages, it is important to acquire the
basics of the local people's language in or-
der to work effectively. Unless your trans-
lator has extensive knowledge of the build-
ing process, it will be difficult to have any
in-depth communication.
Yet in spite of our feeling that we made
several big mistakes, the project in many
ways was a success. The Yaqui workers
from Hermosillo had never worked so
closely with Yaquis from other areas, nor
with foreigners. The process was truly a
communal experience, marked by con-
tinuous problem-solving and endless
laughter. Everybody was learning one or
two of the languages that were being spo-
ken at all times. Yaquis were actively in-
volved in the formulation of the budget
and the purchase of the materials (Kari
1997). Ultimately, the "New House of the
Yaquis" was truly a surprise to everybody.
It was built by the concentrated labor of
the whole community, and because the ef-
fort was demanding of everyone, it left a
deep impression on every person involved.
Top, and top, right: When the reinforcement rods are
fixed in their arched shape, the structure is strong
and resilient.
Above: Expomat mesh fixed under the reinforcement
rods to form a rough surface for the soil-cement
coating layered on top.
Right: View from vault 1 of the proposed entrance
area and the intersection of vaults 1 and 2.
146 147
AFTERWORD
To live in a natural house is a privilege.
Through the process of natural building, we can reconnect with
the basics. We can find simple solutions to seemingly complex
problems, often allowing nature instead of machinery to do the
work. We can create communities that reconnect us with the earth
and with each other, for earth itself is the most wonderful mate-
rial, feeding us and housing us. And to possess knowledge of some
of earth's mysteries is a great gift, allowing enormous freedom.
I hope that all those looking through the pages of this book
draw inspiration to create their own home, and to adapt their
house to its unique, individual, and distinctive environment.
It's your game, it's your joygo and play!
Two of the new owners of the three vault house.
148
BI BLI OGRAP HY
Andr eson, Frank. "Oh Muddy Clay, O Clayish Loam: I nt r oduct i on t o Ger man Clay Building
Techni ques. " Joiners Quarterly: The Journal of Timber Framing and Traditional Building 37
(1997): 18-23.
At Home with Mother Earth. Video recordi ng. Los Angeles: Feat of Clay, 1995.
Beale, Kevin. Factsheet on Straw Bale Construction. Machynl l et h, Wales: Cent re for Alternative
Technology, 1997.
Bedford, Paul, Bruce I nduni , Liz I nduni , and Larry Keefe. Appropriate Plasters, Renders and Finishes
for Cob and Random Stone Walls in Devon. Exeter, U.K.: Devon Eart h Building Association,
1993.
Bee, Becky. The Cob Builders Handbook: You Can Hand-Sculpt Your Own Home. Cot t age Grove,
Oreg. : Gr oundwor ks Press, 1997. Di st ri but ed by Chelsea Green.
Billatos, S. B., and N. A. Basaly. Green Technology and Design for the Environment. London: Taylor &
Francis, 1997.
CRATerre, wi t h Hugo Houben and Huber t Gui l l aud. Earth Construction: A Comprehensive Guide.
Villefontaine Cedex, France: Int ermedi at e Technology Cent re, 1994.
Crews, Carol. The Art of Natural Building: Earth Plasters and Aliz. Kingston, N. M. : Net work
Pr oduct i ons, 1999.
Day, Chri st opher. " Huma n St ruct ure and Geometry, " Eco-Design Journal 3, no. 3 (1995).
. Places of the Soul: Architecture as a Healing Art. Glasgow: Collins, 1990.
Denyer, Susan. African Traditional Architecture: A Historical and Geographical Perspective. New
Y ork: Africana, 1978.
Devon Hi st ori c Building Trust. The Cob Buildings of Devon 1: History, Building Methods, and
Conservation. Exeter, UK: Devon Hi st ori c Building Trust, 1992.
Droege, Sam. ' " How t o' book, 1861," archived in 1997 on CREST' s Straw-bale Listerv: <ht t p: / /
solstice. crest. org/efiiciency/strawbale-list-archive/index. html>.
Easton, David. The Rammed Earth House. Whi t e River Junct i on, Vt : Chelsea Green, 1996.
Escott, Carol, and Steve Kembl e. "Eart hbag Const r uct i on in t he Bahamas. " Earth Quarterly 2
(1997): 24-27.
Farrelly, David. The Book of Bamboo. London: Thames & Hudson, 1996.
Fathy, Hassan. Architecture for the Poor: An Experiment in Rural Egypt. Chicago: University of
Chicago Press, 1986.
Frei, Ot t o. Tensile Structures. Cambri dge: M.I.T. Press, 1969.
Hahn, Tom. "Good Shoes: Foundat i ons. " The Last Straw 16 (1996):1-15.
Har t , Kelly, and Rosana Hart . Video recordi ng. A Sampler of Alternative Homes: Approaching
Sustainable Architecture. Crest one, Colo. : Har t wor ks, 1998.
149
Hi dal go, Oscar L. Manual de Construccion con Bambu: Construction rural - 1. Bogota: Universidad
Naci onal de Col ombi a, 1981. [Estudios Techicos Col ombi anos Ltda., Apar t ado Aereo
50085, Bogota, Col ombi a. ]
Hunt er, Kaki and Doni Kiffmeyer. Earthbag Construction. Moab, Ut ah: OK OK OK, Product i ons,
2000.
Kachadori an, James. The Passive Solar House: Using Solar Design to Heat and Cool Your Home.
Whi t e River Junct i on, Vt.: Chelsea Green, 1997.
Kanuka-Fuchs, Fei nhard, and Jennifer Rat enbury. Biological Natural Organic Paints and Surface
Treatments. Auckland, N. Z. : Building Biology and Ecology Institute of New Zealand, 1991.
Keefe, Larry. The Cob Buildings of Devon 2: Repair and Maintenance. Exeter, U.K.: Devon Hi st ori c
Building Trust, 1993.
Kemble, Steve. How to Build Your Elegant Home with Straw Bales: A Guide for the Owner-Builder.
Bisbee, Arizona. : Sustainable Systems Suppor t , 1995.
Kennedy, Joseph F. The Art of Natural Building: Design, Construction, Technology Compiled from
Presentations at The Natural Building Colloquia Southwest. Kingston, N. M. : Net work
Pr oduct i ons, 1999.
. "Expandi ng t he Hor i zons of Eart hbui l di ng: New Research from t he California Institute of
Eart h Art and Architecture. " Adobe Journal 11 (1994): 16-21.
Khalili, Nader. Ceramic Houses and Earth Architecture: How to Build Your Own. London: Har per 8c
Row, 1986; Los Angeles: Bur ni ng Gate Press, 1990; Hesperi a, Calif.: Cal -Eart h Press, 1996.
. "Lunar St ruct ures Generat ed and Shielded wi t h On-Si t e Materials." Journal of Aerospace
Engineering 2, no. 3 (1989).
King, Bruce. Building of Earth and Straw: Structural Design for Rammed Earth and Straw Bale
Architecture. Sausalito, Calif.: Ecological Design Press, 1996. Di st ri but ed by Chelsea Green.
Mi nke, Gemot . Earth Construction Handbook: The Building Material Earth in Modern Architecture.
Sout hhampt on and Boston: WI T Press, 2000.
Mollison, Bill. Permaculture: A Designer's Manual. Tyalgum, Australia: Tagari, 1988.
Muller, R. "Hesperia' s Domes Pass Seismic Tests." The Daily Press, 30 Sept ember 1993.
Myhr man, Mat t s, and S. O. MacDonal d. Build it with Bales: A Step-by-Step Guide to Straw-Bale
Construction Version Two. Tucson: Out on Bale, 1999. Di st ri but ed by Chelsea Green.
Ner bur n, Ken. Neither Wolf nor Dog: On Forgotten Roads with an Indian Elder. San Rafael, Calif.:
New Worl d Library, 1994.
Nor t on, John. Building with Earth: A Handbook Second Edition. London: Int ermedi at e Technol-
ogy, 1996.
Oliver, Paul. Encyclopedia of Vernacular Architecture of the World. Cambri dge: Cambr i dge Univer-
sity Press, 1997.
Out r am, Iliona. "The Best of Ti mes for Eart h Builders: Research at Cal-Earth. " Adobe Journal 12/13
(1996): 52-58.
. "Int ervi ew wi t h Nader Khalili." Adobe Journal 12/13 (1997): 54.
Panza, Giovani, et al. U Vemela Hiakim Kari, The New House of the Yaquis. Tucson: It om Y oemia
Vetchio, 1997.
Pearson, David. The Natural House Catalog. New Y ork.: Si mon Schuster, 1996.
Potts, Michael. The New Independent Home: People and Houses that Harvest the Sun, Wind, and
Water. Whi t e River Junct i on, Vt.: Chelsea Green, 1999.
BI BLI OGRAPHY
151
Rapopor t , Amos. House, Form and Culture. Engl ewood, N.J.: Prentice Hall, 1969.
Ri chardson, T. L., and E. Lokensgard. Industrial Plastics: Theory and Application. Albany: Delmar,
1989.
Rigassi, V. Compressed Earth Blocks, Volume 1: Manual of Production. Eschborn, Germany: GATE,
1995.
Rudofsky, Bernard. Architecture without Architects: A Short Introduction to Nonpedigree Architecture.
Al buquerque: University of New Mexico, 1964.
Schofield, Jane. Lime in Building: A Practical Guide. Credi t on, U.K.: Black Dog Press, 1994.
Smi t h, Michael G. The Cobber's Companion:-How to Build Your Own Earthen Home. Cot t age Grove,
Oreg.: The Cob Cottage Company, 1998.
Solberg, Gor don. "A Col or ado Papercrete Tour." Earth Quarterly 4 (1999): 14-21.
. "Fi brous Cement : A Revol ut i onary Building Material." Earth Quarterly 1 (1997): 2-15.
. "How To Build a Papercrete Mixer." Earth Quarterly! (1998): 12-18.
Spence, R. J. S., and D. J. Cook. Building Materials in Developing Countries. Chichester and New
Y ork: John Wiley and Sons, 1983.
Steen, At hena, and Bill Steen. The Beauty of Straw Bale Homes. Whi t e River Junct i on, Vt.: Chelsea
Green, 2000.
. Earthen Floors. Elgin, Ariz.: Canel o Project, 1997.
. "The Straw Bale Eart hen House. " Adobe Journal 12/13 (1997): 42-45.
Steen, At hena, Bill Steen, and Davi d Bai nbri dge, wi t h Davi d Eisenberg. The Straw Bale House.
Whi t e River Junct i on, Vt.: Chelsea Green, 1994.
Stern, Ephr ai m. Dor: Ruler of The Seas. Jerusalem: Israel Expl orat i on Society, 1994.
The Straw Bale Solution. Video recordi ng. Santa Cruz, N. M. : Net works Pr oduct i on, 1998.
Stulz Rol and, and Kiran Mukerji. Appropriate Building Materials: A Catalogue of Potential Solutions.
St. Gallen, Switzerland: SKAT Publ i cat i ons, and London: IT Publ i cat i ons, 1993.
Swan, l ames, and Robert a Swan. Dialogues with the Living Earth: New Ideas on the Spirit of Place
from Designers, Architects, and Innovators. Wheat on, Ill.: Quest Books, 1996.
Thomas, Lewis. The Lives of a Cell. New Y ork: Viking Press, 1974.
Thomps on, Kim. , et al. Straw Bale Construction: A Manual for Maritime Regions. Ship Har bour ,
Nova Scotia, Canada: Beautiful Sustainable Buildings, 1995.
Tibbets, Joseph M. The Earthbuilders Encyclopedia. Bosque, N. M. : Southwest Sol aradobe School,
1989.
Tibbies, R. "Building wi t h Hemp. " Building for a Future (1997/ 98): 16.
Trimby, Paul. Solar Water Heating: A DIY Guide. Machynl l et h, Wales: Cent re for Alternative
Technology, 1996.
Van der Ryn, Sim. The Toilet Papers: Recycling Waste and Conserving Water. Sausalito, Calif.:
Ecological Design Press, 1994. Di st ri but ed by Chelsea Green.
Vittore, Phillip. " Dome and Vault Engineering. " Adobe Journal 12/13 (1997): 56.
Woodwar d, I. Nature's Little Builders. Thai l and: Sirivanata Palace Press / Electric Paper, 1995.
Zelov, Chri s, and Brian Dani t z. Ecological Design: Inventing the Future. Video recordi ng. Ecological
Design Project, 1996. Di st ri but ed by Chelsea Green.
Zi esemann, Gerd, Mar t i n Krampfer, and Hei nz Kni eri emen. Naturliche Farben: Anstrkhe und
Verputze selber herstellen. Aarau, Switzerland: AT Verlag, 1996.
150
R E S OU R C E S
P E R I O D I C A L S
Adobe Builder. Sout hwest Sol aradobe School, PO Box 153, Bosque NM 87006 USA. Telephone:
+(505) 861-1255. Int ernet : www. adobebui l der. com .
Adobe Journal. Publ i shed by Michael Moqui n, PO Box 7725, Al buquer que NM. 87194 USA.
Telephone: +(505) 243-7801.
Building for a Future. The Association for Envi r onment -Consci ous Builders. Nant -y Garreg, Saron,
Llandysul, Car mar t henshi r e, SA 44 5EJ Engl and. Telephone: +01559 370908.
Building with Nature. PO Box 4417, Santa Rosa CA 95402. USA. Telephone: +(707) 579-2201.
Designer/Builder. 2405 Maclovia Lane, Santa Fe NM 87505 USA. Telephone: +(505) 471-4549.
Earth Quarterly. Box. 23, Radi um Springs NM 88054 USA. Telephone: +(505) 526-1853.
Eco Building Times. Nort hwest Eco Building Guild, 217 Ni nt h Ave., Nor t h Seattle WA 98109 USA.
Eco Design. PO Box 3981, Mai n Post Office, Vancouver BC V6B 3Z4 Canada.
Environmental Building News. 122 Birge Street, Suite 30, Brat t l eboro VT 05301 USA. Telephone:
+(802) 257-7300, i nt ernet : www. ebui l d. com .
Erosion Control: The Journal for Erosion and Sediment Control Professionals. Publ i shed mont hl y by
Forester Communi cat i ons, Inc., 5638 Hollister # 3 01 , Santa Barbara CA 93117 USA.
Telephone: +(805) 681-1300.
Green Building Digest. Queens University of Belfast, 2-4 Lennoxvale, Belfast BT9 5BY Nor t her n
Ireland. Telephone: +01232 335466.
Green Connections. PO Box 793, Cast l emai ne 3450 Australia. Tel ephone: +(03) 5470 5040.
Home Power. The Hands-on Journal of Home-Made Power. PO Box 14230, Scottsdale AZ 85267-
4230 USA. Telephone: +(919) 475-0830.
Joiners Quarterly. The Journal of Timber Framing and Traditional Building.
PO Box 249, Brownfield ME 04010 USA. Tel ephone: +(207) 935-3720.
Permaculture. Per manent Publ i cat i ons, The Sustainability Cent re, East Meon, Hampshi r e GU32
1HR, Engl and. Telephone: 01730 823311, i nt ernet : www. permacul t ure. co. uk .
Positive News. The Six Bells, Bishops Castle, Shropshi re SY9 5 AA. Engl and.
Telephone: + 01588 630 121/122.
The Last Straw: The Grassroots Journal of Straw Bale and Natural Building. HC 66, Box 119,
Hi l l sboro NM. 88042 USA. Telephone: +(505) 895-5400. e-mail:
t hel ast st raw@st rawhomes. com, i nt ernet : www. st rawhomess. com .
153
The Permaculture Activist. PO Box 1209, Black Mount ai n NC 28711 USA Telephone: + (828) 298-
2812.
O R G A N I Z A T I O N S A N D C O M P A N I E S I N T H E U . S . A N D T H E U . K .
Fr ank Andr esen
Construction with light clays and clay plasters; also offers dry clay products as well as workshops
and consulting.
Kiefernstrasse 2, 4000 Dusseldorf, Germany. Telephone: +0211 7333216.
Kevin Beale.
Design, consultation, and construction using earthbag, straw bale, and other methods.
Ty-Capel-Graig, Talsarnau, Gwynedd, Wales. LL47 6UG, Engl and. Telephone: +(0) 1766 770
696, e-mail: Kevinbeale@breathemail. net.
Black Range Lodge
Videos, educational materials, and resources for straw bale, cob, and other alternative building
techniques. Bed & breakfast lodging for educational retreats.
Star Rout e 2, Box 119, Kingston NM 88042 USA. Telephone: +(505) 895-5652,
i nt ernet : www. epsea. org/ st raw. ht ml
Bui l di ng Biology and Ecology Inst i t ut e of New Zeal and
22 Cust oms Street West, PO Box 2764 CPO, Auckl and, New Zeal and. Telephone: +(64-9) 358
2202.
California Inst i t ut e of Ear t h Art and Archi t ect ure (Cal Earth)
Founded by Iranian Architect Nader Khalili to pursue research in sustainable human shelter
principally through earthen materials and an earthbag technique called "Superadobe" for domes
and vaulted structures. Apprenticeship retreats, and weekend visitations to the demonstration site.
Cal -Eart h, 10225 Baldy Lane, Hesperi a CA. 92345. USA. Telephone: +(1) 760 244 0614, e-mail:
CalEarth@aol. com, i nt ernet : www. Cal ear t h. or g.
Canel o Project
Set up by the co-authors of The Straw Bale House. Offering comprehensive straw bale
construction workshops and educational resources, with a focus on traditional materials and
practices including earthen plasters, floors, and bread ovens. Workshops in southern Arizona and
Mexico.
HC1, Box 324, Elgin, Ari zona 85611 USA. Telephone: +(520) 455-5548, e-mail:
abst een@dakot acom. net , i nt ernet : www. canel oproj ect . com
Cent re for Al t ernat i ve Technol ogy
Workshops and educational resources, with a large bookshop for alternative construction and
sustainable living information.
Machynl l et h, Powys SY20 9AZ, Wales, UK. Telephone: +01654 702400, e-mail: cat@gn.apc.org,
i nt ernet ht t p: / / www. cat . org. uk
RESOURCES
The Cob Cot t age Company
Workshops and resources in cob construction and passive solar design.
PO Box 123, Cot t age Grove, OR 97424 USA. Telephone: +(541) 942-2005, internet:
www. deat ech. com/ cobcot t age
Cons t r uct i on Resources
Specializing in ecological construction techniques. Exhibition center, resources, lectures.
16 Great Guildford Street, London SE1 OHS UK. Tel ephone: +020 7450 2211.
Const r uct i ve Indi vi dual s
Architects specialising in alternative construction, self-build projects, and construction workshops.
London, UK. Telephone: +020 7515 9299.
CRATerre-EAG School of Eart h Const r uct i on
Mai son Leurat, Rue du Lac, BP 53, F-38092, Villefontaine Cedex, France.
CRG Desi gn Heal t hy Homes
Supplier of natural building materials. Design and consultation services.
Cedar Rose, PO Box 113, Car bondal e CO 81623 USA. Telephone: +(970) 963-0437,
e-mail: crose@rof. net .
Devel opment Cent r e for Appr opr i at e Technol ogy
Building code information and educational resources.
Davi d Eisenberg, PO Box 27513, Tucson AZ 85726 USA. Telephone: +(520) 624-6628, e-mail:
infb@dcat.net, i nt ernet : www. dcat . net .
Ear t h Hands & Houses, and PWA Archi t ect s
Design, consultation, workshops and construction of sustainable, ecological, 'organic' projects in
developed and developing countries.
Paul i na Wojciechowska, Architect. 18 The Willows, Byfleet, Surrey KT 14 7QY Engl and.
Telephone: + (0) 1932 352129, e-mail: EHaH@excite. co. uk, i nt ernet :
www. Eart hHan. dsAndHouses. org.
Ear t hwood Bui l di ng School
Resources, workshops, and design consultations for cordwood-masonry construction, stone circles,
mortgage-free living, and off-the-grid energy strategies.
Rob and Jaki Roy, 366 Mur t agh Hill Road, West Chazy NY 12992 USA. Tel ephone: +(518) 493-
7744.
Gour met Adobe
Specializing in clay slips with mica and adobe.
Carol e Crews, HC 78, Box 9811, Ranchos de Taos, NM 87557 USA
Har t wor ks, Inc.
Producers of a two-hour video (see the Bibliography) available in U.S. standard NTSC VHS
format. Includes a section on earthbags, as well as covering other natural building techniques.
Another video specifically on earthbag construction is in production.
Kelly and Rosana Hart , Har t wor ks, Inc. , PO Box 632, Crest one, CO 81131, USA. Telephone:
+(719) 256 4278, e-mail: Office@hartworks.com, i nt ernet : www. hart works. com .
154 155
156
Heartwood School
Johnson Hill Road, Washi ngt on MA 01235 USA. Telephone: +(413) 623-6677.
Willbheart@aol. com
Imagination Works
Dominic Howes, builder and consultant of alternative home construction using earthbags and
other alternative methods.
RO. Box 477, Dr agoon, AZ 85609 USA. E-mail: domi ni chowes@mai l ci t y. com, i nt ernet :
www. sfhet . net / i magi nat i on.
Intermediate Technology Centre
Bookshop and educat i onal resources.
103-105 Sout hampt on Row, London WC1B 4HH, UK. Tel ephone +020 7436 2013.
International Institute for Bau-Biologie & Ecology.
PO Box 387, Cl ear wat er , FL 33757 USA. Telephone: +(813) 461-4371, e-mail:
baubi ol ogi e@eart hl i nk. net , i nt ernet : www. bau-bi ol ogi eusaa. com
Joseph Kennedy
Architectural designer, writer, and peripatetic scholar of natural building and ecological design.
Teaches, gives workshops and consultations.
Star Rout e 2, Box 119, Kingston, NM 88042 USA. Telephone: +(505) 895 5652, e-mail:
l i vi ngeart h62@hot mai l . com.
OK OK OK Productions
Providing earthbag construction, training, along with workshops on wild clay and lime plasters,
earthen floors. Design consultations for dome and arch construction.
Kaki Hunt er & Doni Kiffmeyer, 256 East 100 Sout h, Moab UT 84532 USA. Telephone: +(435)
259-8378, e-mail: okokok@l asal . net .
Out on Bale by Mail (un)Ltd.
Straw bale consultation, educational programs, wall raising supervision, and bulk orders of the
book Build It Wi t h Bales (see the bibliography).
2509 N. Campbel l , #292, Tucson, AZ 85719 USA.
Sustainable Systems Support
Design, consultation, workshops. Specializing in earthbag and straw bale construction methods.
Source of printed and video resources.
Carol Escott and Steve Kemble, PO Box 318, Bisbee, AZ 85603 USA. Tel ephone: +(520) 432-
4292, e-mail: sssalive@primenet. com, i nt ernet : www. bi sbeenet . com/ bui l dnat ur al / .
Women Build Houses
Workshops, referrals, and tool library.
1050 S. Verdugo, Tucson AZ 85745 USA. Telephone: +(520) 882-0985, e-mail:
wbhwbhwbh@aol . com .
RESOURCES
157
E Q U I P M E N T A N D S U P P L I E S
Continuous berm machine for filling earthbags
Can extrude a continuous berm at rates of 10 to 50 feet per minute. "No trenching or stacking
required. With weight typically exceeding 100 pounds per foot, the continuous berm conforms
tightly to underlying soil surfaces, will not blow over, and is extremely difficult to dislodge from
original placement location. Additionally the berm can be cut into sections and stacked for stream-
bank stabilization, 'sand bagging,' fluids containment, or used separately for check structures."
(description from Erosion Cont rol journal.)
Available from Innovative Technologies, PO Box 378, 250 Ha r t f or d Road, Slinger, WI 53086-
0378 USA. Tel ephone: +(414) 644-5234.
Auro Products
For casein, natural paints, oil solvents, waxes, and other finishes.
Sian Company, PO Box 857, Davis, CA 95617-3104 USA. Telephone: +(916) 753-3104,
i nt ernet : www. dcn. davi s. ca. us/ go/ si nan/ auroi nfo. ht ml or www. auro. de/
Livos Phytochemistry of America
Natural, nontoxic paints and stains.
13 Steeple Street. PO Box 1740, Mashpee MA 02649, USA.
Tel: 508 477 7955. www.livos.com for nat ural pai nt s and wood finishes.
Livos UK
Uni t 7 Maws Croft Cent re, Jackfield, Ironbri dge, TF8 7LS UK. Tel ephone: +0 1952 883288
INDEX
A
acidic materials, 81, 83, 92, 106
additions, building, 17, 32-33
additives. See stabilizers
adobe, 4-8, 140
bitumin, use of, 89
cracks allowed, 105
earthbag foundation, 38
finishes, 76, 80, 90
floors, 118-19
furniture, 114
roofs, 66
soil mix, 17, 46, 103, 107
Africa, 6, 16, 18, 19, 22, 142
Ahlquist, Allegra, 56, 127
alis, 95-97, 114, 141
alkaline materials, 81, 83, 84, 106
animal product stabilizers, 79, 82, 106
apses, 22, 26
arched openings, 13, 14, 21, 22, 58-60
arches, xvi, 13, 21-24, 138-39. See also
vaults
for additions, 17
buttresses for, 23-24, 57, 60
corbeled, 26
keystone, 23, 24, 59-60
lancet (catenary), 22-23, 44
unbuttressed, 139
Australia, 10
B
bags. See earthbag bags
Bahamas, 16, 131-34
banana leaf juice, 81
barbed wire, 36, 46, 54, 58, 137
beeswax, 119-20
benches. See furniture
bentonite clay, 88-89
binders. See also clay
casein as, 98-99, 100
in limewash, 97
in paint, 95
as sealant, 93
soil mix using, 103, 105-109
bi t umen, 79, 89
bond beams, 15, 18, 46, 60-63, 66, 79,
123, 127, 130-34
Building Biology and Ecology Institute
of New Zealand, 98
building codes, 4, 14, 90, 105
Bunting, Adrian, 142
burlap bags
for earthbags, 18, 43-45, 76
for insulation, 110
buttresses. See also tension rings
for arches, 23-24, 57, 60
domes, 26, 44, 54-57, 126, 136
dry area, construction in, 35
sand-filled earthbags, 49, 136
spring line, 23, 26
straight walls, 127
C
California, 14-15, 24, 34, 105
California Institute of Earth Art and
Architecture (Cal-Earth), xi v-
xviii, 14, 43, 124
Canelo Project, Mexico, 71-72, 100, 116
casein, 82, 97-100
catenary (lancet) arch, 22-23, 44
cement
bond beams, 46, 79
compression rings, 46, 79
environmental impact, 46, 79, 89, 92
finish stabilizer, 46, 66, 75, 78-79,
89-91, 100-101, 136
stucco, 90, 123, 127
cement-stabilized earthbags, 37, 38, 46,
62, 89, 123, 144-45
Center for Appropriate Technology, 15
Ceramic Houses (Khalili), 21-22, 26
clay-based building materials, 5-6, 19,
46. See also adobe; cob construc-
tion; straw-clay blends
as binder, 6, 103, 105-109
bi t umen used with, 89
interior walls, floors, furniture, 103
moisture control and, 76
soil analysis, 80, 103-105
clay finishes
erosion of, 77
interior plaster, 92
as sealant, 93
waterproofing, use for, 88-89
clay in earthbags, 13, 17, 18, 49
cement stabilization of, 89
damp areas, construction in, 35-38,
49
lime stabilizer use and, 83
polypropylene earthbags, use of, 75
clay slip, 95-97, 114, 141
Cobber's Companion, The (Smith), 70,
104
cob construction, 4, 5, 6, 8-9, 141
earthbag foundation, 16
158
I NDEX
159
finishes, 76, 83, 90, 97
furniture, 114, 115
soil mix, 17, 46, 103, 107-108
thatched roofs, 68-70
Cob Cottage Company, 109
cold climates
building orientation for, 31-32
earthen plasters, effect on, 77
finish stabilizers, use of, 79
hybrid house for, 128-29
insulation for, 111
lime plasters, application of, 87
soil mix for, 106
compass, construction, 34, 48-49
compression rings, 26, 46, 54, 57, 79,
123, 125, 136
concrete. See also cement
bond beams, 18, 60-63, 123, 127,
130-34
foundations, 38, 127, 144-45
connectors. See passageways
Constructive Individuals, xiv
corbeling, 16, 26-27, 43-44, 49, 110,
135
cordwood masonry, earthbag founda-
tion for, 38
costs, 13
Ahlquist square house, Arizona, 127
of earthbag bags, 45
Escott-Kemble house, the Bahamas,
134
Hunter-Kiffmeyer house, 141
Njaya backpackers" lodge, Malawi,
142
Tassencourt dome, Arizona, 125
Yaquis vault house, Mexico, 145, 147
CRATerre, 10, 78-79, 81
Crews, Carol, 82, 90, 95-96, 107
D
damp areas, construction in, 13, 35-40,
49, 66. See also flood-prone
areas, building in; waterproof-
ing; water resistance
finishes for, 75
finish stabilizers, use of, 79
roofs for, 65, 71, 80
design considerations, 13, 17, 29-33, 80
Devon Earth Builders, 90, 106-107
Devon Earth Building Association, 97
Devon Historic Building Trust, 108
disaster-relief housing, 13, 16, 43
domes, xvii, 13, 14, 15
brick, 18
buttressing, 26, 44, 54-57, 136
compass for, 34, 48-49
corbeled, 27, 49, 110, 135, 140-41
defined, 22, 26
earthbags, construction using (See
earthbag construction
methods)
earthquake resistance of, 15
examples, 123-26, 135-42
form, use of, 49
openings [See openings)
for roofs, 66
shell, determining thickness of, 27
spanned, 22
on square structures, 27
stability, increasing, 49
thickness of shell, determining, 27
doors. See openings
drainage, 30, 37, 38, 75, 136
earthen floor, 117
gabions, 30, 39-40
gutters, 140
dry areas, construction in, 35-37, 66
dryboard, 109-10
dry-stone foundation, 40
E
earth architecture, xiv, 3-19. See also
specific building methods, e.g.
adobe
clay-based building materials, 5-6
history of, 3, 5, 6, 22
revival of, 4-5
earthbag bags
cost, 45
making, 45
materials for, 13, 38, 43-45
recycled bags, 44, 45
"seconds," 44, 45, 133, 140
small bags, 52, 137
sources of, 19, 44
earthbag buildings, 13-19. See also
damp areas, construction in;
domes; waterproofing
additions, planning for, 17, 32-33
connecting, 13, 24-25, 136, 139
design considerations, 13, 17, 29-33,
80
in dry area, 35-37, 66
examples, 123-47
finishes (See finishes)
labor intensity of, 13
layout of, 13-14
recycling, 17
seismic and structural testing, 14-15
shape of, 32-33 (See also domes)
utilities, 32, 120-21, 139
Earthbag Construction (Hunter and
Kiffmeyer), 141
earthbag construction methods, xiv, 4,
13, 43-63. See also bond beams;
buttresses; earthbag fill;
foundations; hybrid construc-
tion; openings
appropriate use of earthbags, 16-17
cutting into bag, 17
forms, use of, 25, 49, 58-59, 144-46
for furniture, 18, 114
keying, 36, 54, 137
materials, 44-46
simplicity of, 19
structural walls of conventional
house, 128-29
tamping, 52-54
tools, 13, 46-49
tying courses together, 49, 137
earthbag fill, 16-17, 49-50, 131, 140
cement-stabilized (See cement-
stabilized earthbags) ,
filling process, 45-46, 50-52, 137-39
pH of, 81
i 6 o
earthbag fill, continued
procedure, 140
soil analysis, 80, 103
width of filled bag, 45
Earth Building Association, 88
Earth Construction (CRATerre), 78-79,
81
earthen floors, 103, 107, 115-20
alternatives to, 118-19, 127
construction, 118-19
heating in, 127
insulation in, 111, 116, 117
layers, 116-17
maintenance, 119-20
repair, 120
sealants, 93, 117, 119-20
for upper story, 118
Earthen Floors (Steen), 100, 119
earthen plasters, 66, 75-77, 80
advantages/disadvantages, 76-77
application of, 77-78, 91-92
clay slip (alis) finish, 95-97, 114, 141
for furniture, 114
interior finish use, 92
maintenance, 77, 91, 100-101, 109
nonstabilized, cement plaster on, 90
permeability, 76, 80, 90, 93
sealants, 80, 92-94
stabilizers (See stabilizers)
waterproofing, 66, 88-89
earth-filled tires, 39, 111
Earthmother Dwelling Retreat, xvi-xviii
earthquake resistance, 15, 38, 54-55, 62
seismic testing, 14-15
tire foundation, 39
Egypt, 6, 19, 22
electricity, 32, 120-21
emergency relief, earthbags used for,
13-16, 19, 43
environmental building, xiv, 3-4
erosion, 31, 32, 75, 76, 77, 106
Escott, Carol, 16, 131-34
Europe, 9-10, 68. See also United
Kingdom
expomat mesh, 25, 145, 146
extenders (fillers), 93, 95, 103, 105-109,
114. See also sand
extensions, building, 17, 32-33
exterior finishes. See plasters
external features, 18, 30, 32
F
fiber. See also straw; straw-clay blend
in earthen plasters, 77-78
interior finish plaster, 92
in lime plasters, 83-84
in soil mix, 11, 106-109
fiber composite board, 109-10
fill. See earthbag fill
fillers. See extenders (fillers)
finishes. See also plasters; sealants;
stabilizers
casein, 98-100
floor, 93, 117, 119-20
interior, 92-100
keying in, 76, 86, 87, 126, 133
maintenance, 77, 91, 100-101, 109
papercrete, 101
roof, 66, 73
soil mix for, 106-107
spray application of, 76, 92
fire protection
earthen plasters, 76
insulation, 110
thatch, 70
flood-prone areas, building in, 17, 30-
31, 38, 43, 49
floors
alternative, 118-19, 127
earthen (See earthen floors)
Forschungslabor fur Experimentelles
Bauen, 15
foundations, 15-16, 34-41, 75, 76
concrete, 127, 144-45
in damp areas, 35-40
details, 36-37
in dry areas, 35-37
dry-stone, 40
earth-filled tire, 39
examples, 127, 132, 136, 144-45
flood-resistant, 30-31
functions of, 34-35
gabions, 30, 39-40
ground, connection to, 35
level plane provided by, 33, 47
for non-earthbag buildings, 16, 33,
38
pumice-crete, 40-41
rubble or mort ared stone, 39
site preparation for, 33-34
trench, 35-38
walls, attaching to, 38, 39
France, 9-10
furniture, 18, 30, 32, 103, 114-15
finishes for, 75
soil mix for, 106-107
G
gabions, 30, 39-40
geodesic structure, 130
glass, 139
glue, casein, 82, 97, 98-99
Gourmet Adobe, 82, 90, 96
gravel, 13, 30, 35-38, 46, 49, 50
Great Britain. See United Kingdom
Great Wall of China, 9
greenhouse, 63
Guatemala, 15
gypsum, 81, 82, 86, 92, 114
H
Hartworks, Inc. (Kelly and Rosana
Hart ), 12, 16, 130, 135-39
Hermosillo project, 16, 25, 56, 143-47
Hesperia Museum/Nature Center, 14,
24, 34
hot climates, 31-32, 126, 132-33, 142
Howes, Dominic, 16, 125-29
Hunter, Kaki, 16, 52, 131, 140-41
hybrid construction
Ahlquist square house, 127
earth and straw bale, 112-14
Escott-Kemble house, 16, 131-34
foundations, 16, 33, 38-41
greenhouse, 63
I NDEX 161
Hart dome house, 135-39
Howes conventional-style house,
128-29
I
insulation, 142
earthen floor, 110, 111, 116
foundation, 37, 38
roof, 70, 72-73
scoria as, 136
walls, 50, 110, 112-14, 139, 145
interior finishes, 92-100
interior partitions, 103, 109-10, 114-15
J
jar test, 104-105
K
kaolin, 5-6
Kemble, Steve, 16, 131-34
Kennedy, Joseph R, 15, 16, 18
keying
of earthbag walls with barbed wire/
branches, 36, 54, 137
finishes, keying in, 76, 77, 86, 87, 126,
133
keystone, 23, 24, 59-60
Khalili, Nader, xiv, 14, 15, 21-22, 26, 34,
38, 43, 124, 143
Kiffmeyer, Doni, 16, 52, 131, 140-41
L
lancet arch, 22-23, 44
landscaping, 30, 31, 32
lime-based stabilizers, 38, 46, 78-79,
81-83, 86
lime from coral reefs, 142
Lime in Building: A Practical Guide
(Schofield), 87
lime mort ar recipe, 88
lime plasters, 66, 83-88, 136, 139
alkalinity of, 83, 84
application, 86, 87
capping earthen plasters, 46, 77, 80,
92, 93, 100, 114
casein paint on 99
making, 86-87
permeability of, 82-83, 90, 93
pozzolanic additives to, 87-88
recipes for, 88
water resistance of, 75, 90
lime putty, 97
gypsum added to, 92
making (slaking), 84-86
mixing with sand, 86, 87
limewash, 95, 97-98, 100
linseed oil
lime-wash additive, 97-98
in oil-based paints, 100
as sealant, 93, 117, 119
as stabilizer, 81, 89
lintels, 18, 62
living roofs, 65, 70-71, 140,141
love, role in designing of, xvii
M
maintenance
earthen floors, 119-20
finishes, 77, 91, 100-101, 109
Malawi, 142
manure
l i me/ manure render, 88
manure/wheat flour/sand plaster, 82
Mexico
Canelo project, 71-72, 100, 116
Hermosillo project, 16, 25, 56, 143
47
Obregon project, 25
Save the Children project, 108-109
mica, 92
Middle East, 9, 19, 22, 25, 32
mineral stabilizers, 79, 82-83, 106
moisture
barrier, 30
damage caused by, 90-91
earthbag fill, moisture content of, 46
earthbags, moisture wicked into, 17,
30
permeability/evaporation of (See
walls, breathability)
resistance to (See water resistance)
montmorillonite, 5-6
N
nailer boards, 114-15
natural building, xiii, 4
Njaya backpackers' lodge, Malawi, 142
Nubian vault, 26, 59
O
Obregon project, Mexico, 25
off-the-grid, 32, 126
oil, 81, 115, 117, 119. See also linseed oil
oil-based paints, 100
OK OK OK Productions, 16, 140
openings, 26, 54, 57-60, 138-39. See
also compression rings
arched, 13, 14, 21, 22, 58-60
forms used for, 58-59
in hot climates, 110, 126
square, 57, 58, 60
Ot hona Communi t y Retreat, xiv
Out ram, Iliona, xiv, 14
ovens, 30, 75, 103, 114-15
overhangs, 32, 75, 76, 80
P
paints, 94-100
casein, 99-100
clay slip (alis), 95-97, 114, 141
limewash, 95, 97-98, 100
oil-based, 100
papercrete, 75, 135, 136, 138, 139
plaster mix recipe, 12
properties of, 11-12, 101
as roof covering, 65, 66
parapet-tie wall buttresses, 23
passageways, 24-25, 136, 139
connecting, 13
passive solar. See solar energy
pH, 81, 83, 84, 92, 106
plasters, 16, 19, 25, 126, 139. See also
earthen plasters; lime plasters
application of, 91-92
for burlap bag construction, 76
1 62
plasters, continued
fragmentation of render mass, 91
insulative, 111, 136
interior finishes, 92
moisture permeability of, 76, 80, 90-
91, 93
for polypropylene construction, 75-
76
sand/manure/wheat flour, 82
soil mix for, 106-107
plates. See bond beams
plumbing, 32, 120-21
polypropylene earthbags, 43-45
biodegrading, 17
cement stabilization of fill, 89
finishes for, 75-76
porches, 80
Portland cement, 78, 81, 89, 139
potassium silicate, 94
pozzolanic material, 87-88. See also
pumice
prickly pear juice, 81-82
Pueblo De Sarmiento, 16, 25, 56, 143-
47
Pueblo Indians, 4, 5, 7, 90, 108
pumice, 37, 38, 49, 50, 73, 110, 114
pumice-crete, 38, 40-41
Q
quark, 88, 99
R
rammed earth, 5, 6, 9-10, 38, 76
rammed straw, 111
reinforcement rods, 25-26, 38, 54, 142,
145, 146
remote locations, earthbag use in, 13,
43
renders. See plasters
roofs, 65-73, 80
adobe/brick, 66
conventional, 68, 127
earthbag foundation for, 33
insulation, 70, 72-73
living, 70-71, 140, 141
low-cost flat, 71-73
metal, 145
surface finishes, 66
thatched, 68-70
timber poles, use of, 135, 138, 139
vaulted, 22, 66, 67
water-catchment, 68
wind-resistant, 133
S
sand, 19
in earthbags, 13, 35, 46, 49, 89, 136-
37, 140, 142
in plasters, 82, 83, 86-87, 92, 139
in sealant, 93
in soil mix, 103, 105-109, 114
Save the Children Foundation project,
108-109
scoria, 38, 50, 130, 135, 136, 137-38
screed boards, 118
screens, use of, 32, 80
sculpting. See furniture
sealants, 80, 92-94, 115, 117, 119-20
seismic activity. See earthquake
resistance
Serious Straw Bale (Bergeron and
Lacinski), 70
sick building syndrome, 79, 95
site
landscaping, 30, 31, 32
locating building on, 13, 29-32
preparation, 33-34, 47
topography, 30-31, 34
slaking, 84-86
sloping site, 34
Smith, Michael G., 70, 104
sodium silicate, 93-94
soil for building materials, 80, 103-9.
See also clay-based building
materials; earthbag fill; sand
solar energy, 31, 110, 127, 128, 139
solid buttresses, 23
South Africa, 16, 18
southwestern United States, 6-7, 11-12,
14, 19, 90, 123-27, 130, 135-39
spring line, 23, 26
square construction, 127
square openings, 57, 58, 60
squinches, 27
stabilizers, 46, 78-83, 98, 106. See also
cement, finish stabilizer;
cement-stabilized earthbags;
sealants
application of, 91-92
lime-based, 38, 46, 78-79, 81-83, 86
for waterproofing, 88-89
Steen, Athena and Bill, 11, 108-109,
116, 119
stem walls. See foundations
stoves, 30, 75, 103, 114
straw
in earthen plasters, 77-78
for insulation, 110
rammed, 111
soil mix using, 103, 105-109
straw bale construction, 4, 5
earthbag foundation, 16, 33, 38
finishes, 76, 80
of furniture, 114
hybrid earth and bale, 112-14
for insulation, 72-73, 111-14
roofs, 71-73
straw-clay blends, 6, 10-11, 37. See also
cob
for furniture, 114
for insulation, 72, 110, 111
string lines, 34
structural testing, 14-15
stucco, 90, 123, 127
subfloor, 117
sun, location related to, 13, 31, 80
Superadobe, xiv, 16
sustainable building, xiv, 4
Sustainable Systems Support, 16, 131
T
tamping, 47, 52-54, 139, 140
Tanzania, 142
Tassencourt, Shirley, 123-26
tension rings, 26, 36-37, 54-57
I NDEX
163
tests, soil, 104-105
thatched roofs, 68-70
thermal mass, 31, 50, 91, 111, 113
Three-Vault House, 16, 25, 56, 143-47
tie bars, 24
timber, use of, 33, 62, 135, 138, 139, 144
tires, earth-filled, 39, 111
Tlholego Learning Centre, South Africa,
18
tools, 46-49
topography, 30-31, 34
trust in material, value of, xvii-xviii
U
United Kingdom, 8, 68, 76, 107-108
Utah, 140-41
utilities, 32, 120-21, 139
V
Vaughan, Sue, 130
vaults, 14, 22, 24-26
earthquake resistance, 15
forms used for, 25, 59, 144-46
Nubian, 26, 59
openings to, 58-59
for roofs, 22, 66, 67
three-vault house, 16, 25, 56, 143-47
width to length, ratio of, 25, 67
vegetable stabilizers, 79, 81-82, 106
ventilation, 32, 91, 139, 143-44
W
walls. See also thermal mass
breathability (permeability), 46, 76,
79, 80, 82-83, 90-91, 93, 95,
106
fragmenting, preventing, 137
interior partitions, 103, 109-10
retaining, 30, 39
straight, 55-56, 60, 127-29
water added to earthbag fill, 46, 47
water-catchment roofs, 68
water glass, 93-94
waterproofing, 32, 36-37, 60, 75-76, 80,
141. See also drainage; finishes;
flood-prone areas, building in;
overhangs; water resistance
bricks, 66
damp-proof membrane, use of, 38,
60, 70, 136
earthen floor, 117, 119-20
roofs, 66, 68-70, 73
sealants, 93
stabilization for, 88-89
water resistance. See also waterproofing
clay-based soil mix, 106
earthen floor, 119
papercrete, 12, 75, 101, 136
stabilizers for, 78-83
wattle and daub, 4, 6, 10
waxes, 115, 119-20
weatherproofing. See waterproofing;
water resistance; wind activity
wheat flour paste, 81, 82, 96, 97
whitewash. See limewash
wind activity, 32, 54, 62, 80, 132-33
windows. See openings
Wisconsin, 128-29
Y
Y aqui house, Mexico, 16, 25, 56, 143-47