Ferro Manual Draft
Ferro Manual Draft
Ferro Manual Draft
A Design and Construction Manual for Wire-Reinforced, Jar Shaped Water Tanks
Carmelo Gendrano
Christopher Hillbruner
Many people from the U.S. Peace Corps-Philippines have provided valuable as-
sistance in the creation of this manual. We would like to particularly thank Peace Corps
staff members Stella Giondonko, Mary Abalarde and John Borja and the Group 259
Water/Sanitation volunteers Reynaldo Pellos, Karla Acayan and Kristopher Dodge for
their help and support.
We would also like to thank other Philippines RPCVs, including Jeff Kirshberg
and Mike Lilless, whose photographs and reports helped to round out this manual.
Table of Contents
Introduction 5
Who Can Use This Booklet? 5
What is ferrocement? 6
Are there different types of ferrocement tanks? 6
Part V CD-ROM
Construction Video
Tank Volume Estimator Piped Water System
Tank Volume Estimator Rainwater Catchment
Tank Materials Estimator
Form Materials Estimator
6 Building a Jar Shaped Ferrocement Tank
Introduction
What is ferrocement?
Ferrocement consists of metal reinforcement sandwiched between thin layers of cement. Differ-
ent types of reinforcement are used including wire, wire mesh and steel bar. Ferrocement can be used
to construct a wide variety of structures including boats, houses, and grain silos.
One particularly popular use for ferrocement is water tank construction. Ferrocement resists
cracking very well and due to its thinness, ferrocement uses very little cement. This means that ferro-
cement tanks are both lighter and less expensive than traditional poured concrete tanks while still being
comparably strong. Ferrocement tanks are also more durable, more hygienic, need less upkeep and are
often cheaper than metal water tanks.
Yes, there are a variety of different designs. The oldest and most common design is a cylindri-
cal tank. For this method, a framework of steel bar and wire mesh is constructed. A concrete floor is
poured and the framework is plastered with a number of thin layers of cement mortar. The tank is com-
pleted with the construction of a flat or domed lid. Another method for constructing a cylindrical tank
utilizes a removable form, constructed of corrugated G.I. sheets. In this case reinforcement is provided
by a combination of wire mesh and heavy steel wire (2.5mm).
This type of tank is also referred to as a singly curved tank because while it is round horizon-
tally, its vertical walls are straight.
Other ferrocement tank styles include the Thai Jar, the Sri Lankan pumpkin tank, and the
Wire Reinforced Jar. All three of these designs are referred to as doubly curved tanks, because they are
rounded both horizontally and vertically.
Research has shown that doubly curved tanks have a number of benefits. First, they are stronger
than singly curved tanks. Second, doubly curved wall tanks utilize less material and therefore can be
less expensive. (Turner, 2000) Finally, doubly curved walls help to prevent cracking, especially at the
bottom of the tank where the walls meet the base.
The Thai Jar design was developed in the 1980s. This design is typically used for smaller, indi-
vidual household tanks ranging in size from 400l to 3,000l. Rather than using a metal mold or form, the
tank is constructed around a specially sewn cloth or plastic bag that has been filled with sand or rice
husks. Layers of cement are plastered onto the form. Once the cement has dried, the sand is removed
from the sack, the sack is removed from the tank and cement slurry is applied to the inside. Because
Thai Jar tanks are usually small, they dont always need wire or mesh reinforcement between the layers
of mortar. However, some tanks do use metal reinforcement. Technically, tanks without such reinforce-
ment are not ferrocement. This design is often the simplest and most cost effective option for very
small tanks (less than 0.8m3)
The Pumpkin tank was developed in Sri Lanka during the mid 1990s as part of a rainwater
catchment promotion program. Its design and construction technique are in many ways similar to the
cylindrical tank. But, unlike cylindrical tanks, it has doubly curved walls, uses less cement and is con-
structed using a removable iron bar framework. Because the form is removed it can be reused for mul-
tiple tanks, thus lowering the overall cost of tank construction.
Finally, there is the Wire Reinforced Jar design, developed in The Philippines, also in the mid
1990s. Like the pumpkin tank it utilizes curved walls and a removable, reusable steel bar form. How-
ever, it is different from other tank designs because it uses thin wire wrappings for reinforcement and
not wire mesh, iron bar or heavy steel wire. It also uses less cement than other doubly curved tank de-
signs. These differences can result in significant cost savings. In addition, while the Pumpkin Tank
does use a removable form, it must be rebuilt, piece-by-piece, each time a tank is constructed. Not only
is this time consuming, but it makes it more difficult to achieve a proper alignment. The Wire Rein-
forced Jar design uses a welded form that has been cut into manageable pieces. Form setup is faster and
a more consistent tank shape can be easily achieved.
The Wire Reinforced Jar design can be used for a wide range of tank sizes. In the Philippines,
this method has been used for tanks as large as 40,000 liters. Thus, it can be used for a wide range of
applications, from single family home rainwater catchment systems to large piped water systems.
In order to support the ferrocement while you are building the tank, you must construct a form
out of iron bar and wire mesh. This form will be removed once the tank has dried and can be used
again in constructing future tanks.
You will need the following tools and materials to construct the form.
Materials
Steel Bar (8mm or 10mm) Choosing Iron Bar
wire mesh
#18 Tie Wire Forms for Jar shaped tanks can be built
Welding Rod from either 8mm or 10mm iron bar.
Old newspapers Each size has its advantages and disad-
Cassava or laundry starch vantages. 8mm is cheaper and easier to
bend into shape, but forms made of
Tools 8mm are also less durable. On the other
Hacksaw hand 10mm forms will be stronger, but
Tape Measure they are more expensive and more diffi-
Hammer cult to build. Generally, forms for tanks
Pieces of scrap lumber of 5,000 liters or less can be built with
Chalk the 8mm size. Larger forms, or forms
Nail and string that will be used extensively should use
Wire Cutters 10mm iron bar.
Welding machine
Paint brushes
Building a Jar Shaped Ferrocement Tank 11
Once you know the dimensions/shape of your tank and have all the necessary tools and materi-
als, you are ready to begin building the form.
Vertical Pieces
1. You should know the diameter of your tank (D). The circumference of your tank (C), can be found
by multiplying the Diameter (D) by (3.14).
D=2
= 3.14
C = D x = 2 x 3.14 = 6.28m
2. You need one vertical piece every 20cm. You also need extra vertical pieces because you will be
cutting the form into sections. (this could use illustrationFig. 1) To determine the number of ver-
tical pieces needed, multiply your circumference by seven.
C = 6.28
# of verticals = 7C = 6.28 x 7 = 43.96 = 44
3. Cut a piece of iron bar, of the proper length, for each vertical piece you need. Using chalk, draw the
shape of your vertical pieces on a flat concrete or wooden surface. Then, using a hammer and the
pieces of scrap lumber, bend the iron bar into the proper shape.
Horizontal Pieces
H = 2.1
# of horizontals = (H/.45) + 1 = (2.1/.45) + 1 = 5.667 6
2. The horizontal pieces will be ring shaped and most of them will equal the circumference (C) in
length. Keep in mind however, that because the form curves in at the bottom, the iron bar hoops at
the bottom will be slightly smaller than those higher up.
3. Using a nail, the string and the chalk, draw circles that are the same size as the horizontal hoops
you need on a flat concrete or wooden surface. Using the same method used for the vertical pieces,
bend pieces of iron bar into the proper shape.nse
4. Once you have cut and bent all your pieces, take the largest hoop and mark it every 20cm, this will
show you where the vertical pieces go.
Fig. 3.1 and 3.2 Bending Horizontal Pieces and Vertical Iron Bar Location
4. Then, take the pieces to a welding shop and have them welded together.
5. Once the form is welded, cut the frame into pieces. These pieces must be small enough to fit
through the maintenance hatch on the top of your tank. You may want to add some additional sup-
ports on the inside of the frame pieces.
Fig. 5 and 6 Iron Frame Piece: Diagram and Photograph (Note highlighted supports)
6. Finally, cover each piece with 1 wire mesh. Be sure the mesh is stretched tightly across the frame
and tie it to the form with wire.
7. The form can be transported in pieces. Then, at the worksite, cover the wire mesh with pieces of
newspaper dipped in a mixture of cassava starch (or flour) and water. Let the paper dry. This layer
of paper will prevent the cement from sticking to the form.
6. When you are ready to begin construction, assemble the pieces. Climb inside and tie the iron bar
together with wire.
You will need the following tools and materials to build you tank.
Materials
Screened, non-calcareous sand
Gravel
Portland Cement
Sahara waterproofing compound
#18 Tie Wire
6mm Iron Rebar
Pipe fittings of appropriate size (1 inlet, 1 outlet, 1 overflow)
Flat Galvanized Iron Sheet
Tank Form
Tools
Wire Cutters
Hacksaw
Shovels
Buckets
Tin Snips
Screen
Masonry Spoons
Extra Cement Sacks or Newspapers
Sand for ferrocement should be non-calcareous, meaning that it does not come from lime-
stone or broken down coral. These types of sand tend to cause a lot of cracking. Generally, avoid-
ing calcareous sand means using river sand and not beach sand.
If calcareous sand is your only option, use a richer mix of cement for your tank, 1:2 for the
1st layer and 1:2.5 for subsequent layers. To see if you have achieved a usable mix, apply a thin
coat of mortar and let it dry. If it only has a few cracks and does not crack further upon the appli-
cation of a second coat, you should be fine.
Additionally, you can use a pozzolan cement for the final inner layer of mortar or paint the
inside with natural or acrylic latex. Both options will provide additional protection against crack-
ing and leaking.
All sand, regardless of its source should have good size distribution, meaning that your
sand particles have a variety of sizes, some coarse, some fine, some in between. This will mini-
mize the spaces between the sand particles and allow you to use less cement.
Finally, be sure to wash your sand well with clean water before mixing with cement.
Washing will remove salts and organic debris which may compromise your mortar.
16 Building a Jar Shaped Ferrocement Tank
1. The first step in constructing the base is to make sure the area is clean and level.
2. Then, dig a circular hole, 0.1m deep, as large as the bottom of your tank. Around the inner edge of
the hole, dig a trench 0.1m wide and 0.1m deep. Line the bottom of the hole with large gravel.
3. To strengthen the base, form a hoop out of iron bar that is a little smaller than your hole. Then, add
wire reinforcement every 0.1m. Be sure to leave 0.15m of excess wire hanging off on both sides.
Then place the iron bar ring in the hole on top of the gravel.
5. Once the reinforcement is in place, mix a batch of cement (3:2:1) with Sahara and pour the base.
Make sure the excess wires are not covered by cement. Let the base cure overnight.
1. When the base is dry, set the iron bar form on top. Be sure that the wires sticking out from the base
are not caught under the frame. Wrap the form in #18 wire every 10cm. This will help hold the
form together and give the cement something to grab onto.
2. Using wire, attach the hardware for your tank to the frame. You should have a clean-out valve on
the bottom, an intake XXcm from the top and an overflow xxcm from the top.
3. Mix a batch of rich cement with screened sand (no gravel) and Sahara. The ratio of cement to sand
should be 1:2.5. Add just enough water so that the mortar is workable. Too much water will make
the cement weaker and difficult to plaster.
4. Then spread a thin rough layer, about 8mm thick, over the whole tank. This will form the rigid shell
over which the subsequent layers are built.
5. Construct the inner form for the tank lip. This form should be ring
shaped, with an outer diameter of 60cm and a height equal to 5cm
plus the estimated thickness of the roof. Once the first layer has
been applied, center the form over the tank opening.
1. The next day, mix another batch of cement using 1 part cement for every 3 parts sand. Plaster an-
other thin layer (6mm) filling in the unevenness of the first layer. This second layer should cover
the walls and part of the roof (from the edge of the roof to 0.8R from the roof center)
insert pic.
1. Next, attach the vertical wire supports. These wires help strengthen the tank against sway stress,
like the kind caused by earthquakes. They also connect the tank walls to the base.
2. First, count the number of wires you have sticking out of the bottom of your tank (base wires). Di-
vide this number by three to get the spacing for your vertical wires; we will call this number X.
3. Then, attach the end of a spool of wire to one set of the base wires. Run the wire up and over the
tank and attach it to the bottom of the tank on the other side. You should attach it to the set of wires
which is X number of wires from where you started.
4. Continue running the wire up and over the tank and attaching it to the base wires until you have no
attachment points left.
5. NOTE: Finding a value for X that works sometimes requires some trial and error. To avoid wasting
too much time, it is advisable to check on paper first whether your X value will work.
Building a Jar Shaped Ferrocement Tank 19
Example: Your tank has 32 pieces of wire sticking out if the bottom.
However, 10 does not work. Using this number, we would keep hitting the same sets of base
wires repeatedly. Therefore, we will try 11.
In order to help support the walls, horizontal wiring needs to be wrapped around the tank. These
wires should be placed directly over the vertical wires. This presses the verticals as close to the mortar
as possible and maximizes the load transfer between the two sets of wire reinforcement. Placing the
horizontal wires just before the final layer of mortar makes also enhances their effectiveness as well as
minimizing the possibility that water might seep through and undermine the tank by causing the wires
to rust.
However, water in a tank does not exert equal pressure on the sides of the tank. There is less
pressure near the top and more pressure towards the bottom. Therefore, the density of wire wrapping is
highest towards the bottom of the tank and lowest towards the top. Using a series of mathematical
equations one can determine the most cost effective density of wire wrapping. Details regarding this
method can be found in the appendices. An effective, and simpler method is described below.
1. Attach four equally spaced strips of wire mesh to the tank. These will serve as spacing guides.
2. Wrap one end of a roll of 16 gauge around the based of the tank and tie it snugly to itself. Then take
the rest of the roll and wrap it tightly around the tank following the guidelines below.
3. The wire should be continuous. When one roll runs out, tie the end to a new roll and continue.
4. When you reach the top spiral back down and tie off to the original loop.
Building a Jar Shaped Ferrocement Tank 21
3. Once the wrapping is completed, put more mortar on the roof until it has reached its required thick-
ness. (3cm if the roof has a diameter up to 180cm, proportionally thicker if roof diameter is more)
4. Next, plaster the entire tank with a third layer of mortar (1:3) 6mm thick. Note: This final layer
should be even but not completely smooth. A very smooth final layer makes it difficult to patch any
cracks which might develop.
3. Finally, construct the outer form for the lip of the tank. It should be circular with a radius of70cm
and a height of 5cm. Place the form on top of the tank, centered on the inner form. In order to save
cement, put down a layer of medium sized rocks. But be sure to leave enough space between the
stones so that the lip connect to the roof of the tank. Then fill the forms with cement (1:4).
1. The next day, remove the ring form from the top of the tank.
2. Climb inside the tank and cut the wires holding the form pieces together. Remove the form pieces
and as much newspaper as possible. Use a wire brush to remove any paper that will not peel away.
3. Apply a final layer of cement on the inside of the tank (floor and walls) and then let the entire tank
cure for at least 1 week. Remember that using pozzolan cement for this final layer can help reduce
leaking if calcareous sand was used. While the tank cures, keep it wrapped in sacking or plastic. Twice
a day, morning and evening, remove the covering and wet the tank down.
4. After 1 week, begin filling the tank. On the first day fill it to a depth of 30cm. On each subsequent
day, add 15cm of water until the tank is full.
5. If any leaks develop, simply drain the tank and patch the cracks with mortar
Building a Jar Shaped Ferrocement Tank 23
Jar Shaped/Wire
Cylindrical Ferrocement 2 Poured Concrete
Price Reinforced 1
TANK (Php) Quantity Total Quantity Total Quantity Total
Portland Cement (40kg sack) 120 9.20 1104.00 15 1800.00 29.28 3513.00
Sand (cubic meter) 600 0.78 468.00 1 600.00 1.96 1174.50
Gravel (cubic meter) 600 0.05 30.00 0.5 300.00 3.92 2349.00
Sahara Waterproofing Compound 27 9.20 248.40 15 405.00 29.28 790.43
#18 Tie Wire (kg) 35 22.79 797.65 0 0.00 6 210.00
8mm Iron Rebar 75 4.00 300.00 0 0.00 75 5625.00
2"dia x4" GI nipple w end cap 50 1.00 50.00 1 50.00 1 50.00
1/2"x3" GI nipple, coupling and faucet 100 2.00 200.00 2 200.00 2 200.00
3" san PVC elbow 35 1.00 35.00 1 35.00 1 35.00
1"x3"GI nipple w plug 50 1.00 50.00 1 50.00 1 50.00
2"dia x4" GI nipple 40 1.00 40.00 1 40.00 1 40.00
2" gate valve 500 1.00 500.00 1 500.00 1 500.00
3"dia x4" GI overflow pipe with elbow 45 1.00 45.00 1 45.00 1 45.00
3mm screen, m 125 1.00 125.00 1 125.00 1 125.00
2.5mm wire 75 0.00 0.00 5.00 375.00 0 0.00
Chicken Wire 40 0.00 0.00 16 640.00 0 0.00
GI Sheet 176 0.00 0.00 4 704.00 0 0.00
Angle Iron 150 0.00 0.00 2 300.00 0 0.00
3993.05 6169.00 14706.93
5% 199.65 308.45 735.35
Total 4,192.70 6,477.45 15,442.27
FORM
10mm Iron Bar 95 45 4275
1/2" Wire mesh 125 25 3125
Lumber 10 0 200 2000
Angle Iron 150 0 3 450
GI Sheet 176 0 16 2816
Hardware 100 1 100 1 100
Total 7,500.00 3,366.00 2,000.00
Grand Total Tank 1 11,692.70 9,843.45 17,442.27
Tank 2 15,885.41 16,320.90 32,884.54
Tank 3 20,078.11 22,798.35 48,326.81
Tank 4 24,270.81 29,275.80 63,769.09
Tank 5 28,463.51 35,753.25 79,211.36
Tank 6 32,656.22 42,230.70 94,653.63
1
Estimate based on Ferrocement Tank Estimator worksheet
2
Estimate based on a materials list for a 10m3 cylindrical tank with a GI roof in S.B. Watts Ferrocement Water Tanks and
Their Construction
24 Building a Jar Shaped Ferrocement Tank
Fig. 1 Cylinder
2. The ratio of the cylinders height to its diameter (H/D) should be between 0.5 and 2.0. This will en-
sure that you construct a stable tank. First, choose a height and solve for the area of the cylinders
base. (2.1m is a good height for tanks 4,00010,000 liters.)
V = A x h so, A = V / h
Where,
V = Volume
A = area of circle
h = height
3. Once you have determined Area (A), use the following equation to determine the diameter (D).
Where,
A= Area of the circle
D= Diameter of the circle
= Pi (3.14)
4. Then, check to make sure that the ratio of Height to Diameter (H/D) falls between 0.5 and 2.0.
Building a Jar Shaped Ferrocement Tank 25
Example: You are building a 4,000-liter tank (4m3). You choose 1.5m for your height.
V = 4m3
h = 1.5
1. The next step is to calculate the curves that give the tank its jar shape. For the top, draw the top as a
rectangle, leaving a 0.6-0.8m opening for a maintenance hatch.
2. Then, draw the top of the tank; it slopes down 1-2cm for every 10cm of distance (slope = -1/10).
3. Finally, at the edge, it curves downward to meet the vertical wall of the tank. This curve has a ra-
dius of 0.1-.3m (the smaller radii can be used for smaller tanks).
26 Building a Jar Shaped Ferrocement Tank
4. Next, you need to determine the curve of the tank bottom. First, draw the bottom of the tank as a
rectangle and draw a horizontal line at the tanks mid-point. Label the beginning of this line as
Point A. Extend this line past the edges of the tank.
5. Then, draw a line with an angle of 20 from the lower left hand corner of the tank (Point B) and
extend it until it crosses the line you just drew at the tank mid-point. Label the intersection of these
two lines as Point C.
Building a Jar Shaped Ferrocement Tank 27
6. Line AC is the radius of the curve at the bottom of the tank. To find the shape, draw the arc from
Point A to Point B.
7. The 20 degree limit is to assure that the mortar will not fall off while it is being applied by trowel
on this section of the form .
28 Building a Jar Shaped Ferrocement Tank
8. Finally, combine your calculations for the top and bottom to get the complete shape of your tank.
This is also the shape and size of the vertical iron bar pieces youll need to build a form.
Mullins, Dan. How to Build Ferrocement Tanks. Swaziland: Ministry of Education, 1988.
Sharma P.C. and V.S. Gopalaratnam. Ferrocement Water Tank. Bangkok: International Ferrocement
Information Center, Asian Institute of Technology, 1980.
Turner, Stephan. Design of Rainwater Storage Tanks for Use in Developing Countries. Diss. Univer-
sity of Warwick, 2000.
Watt, S.B. Ferrocement Water Tanks and Their Construction. London: Intermediate Technology Publi-
cations, Inc., 1978.
Building a Jar Shaped Ferrocement Tank 37