A Guide To The Repair of Historic Brickwork
A Guide To The Repair of Historic Brickwork
A Guide To The Repair of Historic Brickwork
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This guide will help you care for your historic brickwork by
giving advice on:
detecting problems in brick walls
repairing damaged brickwork
repointing historic brickwork
cleaning brickwork
getting the right advice
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bricks
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DUBLIN
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or through any bookseller
Contents
INTRODUCTION
1. A SHORT HISTORY OF IRISH BRICKWORK
Georgian brickwork
10
13
Types of brick
14
15
16
17
18
21
22
Decorative brickwork
25
Polychromatic brickwork
26
27
Stoneware products
27
28
28
29
30
Brickwork decay
32
4. REPAIRING BRICKWORK
35
35
36
41
43
Cleaning trials
44
Cleaning methods
45
46
6. GLOSSARY
49
Introduction
The character of many of our historic buildings owes
much to the quality of their brickwork. Fired ceramic
brick has been used in Ireland since the sixteenth
century and is a versatile, attractive, and durable
material requiring no surface sealants and minimal
maintenance. Brickwork is well suited to the Irish
climate; it ages well, mellowing in colour over time,
and will last for centuries, provided it has been
properly made, detailed, and laid.
Most brick found in historic Irish buildings is of local
origin. Brickmaking skills were developed in Ireland
during the sixteenth and seventeenth centuries, and
bricks were made from local clays in all parts of the
country until well into the twentieth century and are
still manufactured in some places today. Bricks were
(and still are) also imported, particularly machinemade brick in the latter half of the nineteenth century.
However, historically, transport and cost factors
generally confined the use of imported material to
faades and the parts of buildings that could be seen.
During the eighteenth and nineteenth centuries, brick
became the material of choice for constructing and
facing buildings in Dublin and other coastal cities and
towns. In inland areas, brick was used in combination
with stone for lining walls, forming openings, vaulting,
and in chimney and fireplace construction. Brick is still
manufactured in Ireland and both home-produced
and imported brick remain popular materials for
facing buildings in the twenty-first century.
The beauty and versatility of brick have made it a popular construction material in Ireland, and throughout the
world, for many hundreds of years
KILNS
Moulding
Drying
Georgian brickwork
The use of brick as a material suitable for buildings of
high architectural quality was considerably enhanced
in the early eighteenth century by the work of Edward
Lovett Pearce (1699-1733), Surveyor General, and
Irelands most important architect of the period. His
confident use of brick was influenced by his travels
and knowledge of brick buildings in Italy and the
Netherlands. He was also author, in 1730, of the first
Irish Act of Parliament (3 Geo.II. c.14) that incorporated
quality control measures for brickmaking. It also
specified a size for bricks made for commercial
purposes in Ireland, although interestingly, the bricks
found in Irish buildings of this time are not generally
of the specified dimensions.
Ruined garden house of brick at Newbridge House
Demesne, Co. Dublin
10
Conservation principles
In a sense, we look after our historic buildings for those who come after us. Many
of these buildings have been around for generations before us and it is our
responsibility to hand them on in good condition to allow future generations to
enjoy them too. In order that the works you undertake do not damage the special
qualities of a historic building, it is important to understand some of the basic
principles of good building conservation. Many of these are common-sense and all
are based on an understanding of how old buildings work and how, with sensitive
treatment, they can stay special.
Before you start, learn as much as you can about your particular building. What is
its history? How has it changed over time? Remember that later alterations may be
important too and evidence that the building has been cared for and adapted over
the years with each generation adding its own layer to a unique history.
> Do use the acknowledged experts - get independent and objective advice from
the right people and only employ skilled craft workers with proven experience
in the type of work required
> Do repair the parts of the building that need it - do not replace them unless
they can no longer do the job they were designed to do
> Do make sure the right materials and repair techniques are used and that even
the smallest changes you make to the building are done well
> Do use techniques that can be easily reversed or undone. This allows for any
unforeseen problems to be corrected in future without damage to the special
qualities of the building
> Do establish and understand the reasons for failure before undertaking repairs
> Do record all repair works for the benefit of future owners
> Dont overdo it only do as much work to the building as is necessary, and as
little as possible
> Dont look at problems in isolation consider them in the context of the
building as a whole
> Dont use architectural salvage from elsewhere unless you are certain that the
taking of the materials hasnt caused the destruction of other old buildings or
been the result of theft
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12
13
Brick terminology 1
Types of brick
The types of brick found in Irish buildings fall into two
main categories: they are either handmade or
machine-made.
Handmade bricks were, as the name suggests,
moulded in individual boxes by hand, dried, and then
fired either in temporary clamp kilns or permanent
kiln structures. All traditionally made bricks were
graded, according to their suitability for use, into three
main types. The best bricks were selected for facing
work. In Ireland, these were generally described as
stock or facing bricks. General brick suitable for
building work but not for facing brickwork was called
place brick or common brick. The rest of the bricks
from the kiln were either over-burnt and misshapen
(clinkers) or under-burnt and were generally unusable
for anything other than rough or non-structural work.
Machine-made bricks are those made by a
mechanised process, such as an extruded wirecut,
pressed and simulated handmade. Machine-made
bricks can be solid, perforated, or panelled and are
often stamped with the makers name.
14
These are special, high quality bricks made from topmost silica-bearing brick earth or clay. They are
low-fired, or baked, to a point just short of chemical
change or vitrification. This creates a soft textured
brick, yet one that is strong enough to be cut and
rubbed for some types of highly-skilled ornate work,
such as moulded cornices and string courses,
architraves, columns and arches; and capable of good
weathering provided the work is properly detailed.
Since the late nineteenth century, rubbers were often
made oversized to allow for cutting to shape in a
shaped box using a bow saw fitted with a twisted wire
blade. As far as present research suggests, these were
never produced in Ireland.
ENGINEERING BRICKS
These bricks are manufactured from a natural deposit
of a clay type that, when fully fired, naturally creates a
strong, dense, non-porous and generally smooth, blue
or red coloured, face. Their popular use developed in
the nineteenth century for civil engineering
applications such as bridges, viaducts, platforms, and
tunnels. They were also used in domestic and smallscale buildings for aesthetic reasons where their
colour gave a visual contrast with the general bricks
used.
GLAZED BRICKS
The early glazing of bricks came about as a direct
result of the combination of wood fires and high
temperatures against the face of the bricks in the
firing tunnels. These bricks were then used to create
decorative patterns within a brick wall, including
diaper work. Later glazed bricks were machine-made,
usually with one glazed surface. The earliest were
termed salt-glazed and were generally brown in
colour. Later developments in the mid nineteenth
century led to the fired brick being dipped into a
prepared solution of liquid clay. This was usually white,
but could be pigmented to create a wide range of
colours and then re-fired at a higher temperature.
Glazed bricks were often used, because of their lightreflecting and self-cleansing qualities, on shop fronts,
toilets, dairies, and light wells in the nineteenth and
early twentieth century buildings.
15
16
17
COLOUR WASHING
Colour washing of the brickwork of the principal
faades was common practice in Ireland, and was used
from the seventeenth century onwards. This practice
was also known as raddling or ruddling. It was
primarily used to regularise the varying tones of
clamp-fired and early kiln-fired bricks. It also gave a
small degree of protection to soft handmade bricks
and slow-setting lime mortars.
Colour washes were made using natural ochres,
combined with glue size and a fixative such as alum or
copperas. Generally colour washing was also
historically combined with white painted lines, termed
pencilling, made of distemper (a mix of crushed chalk
and glue size) applied over part of the ochred joints in
order to re-define them, but to a lesser scale. This can
be seen in the fine eighteenth-century brickwork ruins
of The Hellfire Club at Desmonds Castle, Askeaton,
County Limerick.
18
(i)
Flush joints
(ii)
(i)
(ii)
Ruled joints
Wigged joints
Struck joints
This pointing
technique is carried
out in a number of
stages. A coloured
stopping mortar is
applied and then
grooved to receive a
later application of
the tuck
Weather-struck
and cut joints
19
FLUSH POINTING
These joints are generally plain and finished flush
and flat to the wall face with a trowel as the walling
is constructed. From the early seventeenth century
onwards, the joints could also be lightly grooved, or
ruled using a thin-bladed instrument called a jointer
to the centre of the horizontal and vertical joints,
guided level and plumb, by the timber pointing-rule
or feather edge.
RULED POINTING
Ruled joints are flush joints which are then cut by
running a thin-bladed instrument called a jointer
along the centre of the joints, guided level and plumb
by the use of a pointing rule, to ensure a level and
plumb profile. This finish is also called by the later
terms penny-round or joints-jointed. On some historic
brickwork, after the faade was colour washed, the
groove was highlighted with a painted white line of
distemper in a process termed pencilling.
i)
20
TUCK POINTING
STRUCK
RECESSED
The use of slightly recessed flush joints can be found
in buildings built with machine-made brick in the
twentieth century.
WINDOW OPENINGS
CHIMNEYS
One of the earliest uses of brick in Ireland was for
ovens, fireplaces, and chimneys. As an already fired
product with heat absorbing properties, brick was
suitable for any location subject to extremes of
heating and cooling. Using similarly shaped masonry
units to construct a chimney was also undoubtedly
easier than using irregular-shaped quarried stone. For
these reasons, on many buildings of stone or mud-wall
construction, the only externally visible brickwork
feature will be the chimney. Chimneys are generally
the most exposed parts of any building and have to
cope with persistent wetting and drying, and heating
and cooling cycles, as well as years of wind and frost
action that all take their toll on the brickwork. In
addition, the brickwork can suffer the chemical effects
of the sulphurous by-products of coal fires.
22
BRICK VAULTING
In Ireland the vaulting-off of basement floors in brick
became an accepted form of construction from early
in the seventeenth century. This is a very strong
building form and can support heavy upper floor
finishes, such as stone, marble slabs, bricks or thick clay
tiles. The use of vaulting eliminated the need for
timber construction at ground floor level. This was
particularly advantageous for fire protection, as it
separated potential sources of fire, such as kitchens
and service areas in the basement, from the upper
floors. In addition the qualities of the arched shape,
combined with the overall thickness of the brick
construction of the vaulting, provided useful sound
proofing between floors.
Skilfully built (or turned) over a carefully positioned
temporary timber framework (or centre) of suitable
size, one of the earliest examples of ribbed vaulting, or
cross vaulting in brick, is found in the undercroft of
Jigginstown House. This general method of
construction became more widely adopted during the
eighteenth century; when most buildings with
23
INTERNAL BRICKWORK
Internal walls of brick, timber-framed walls infilled with
brick (known as nogging), and brick wall linings are
frequently seen in Irish buildings of the eighteenth
and nineteenth centuries. In nearly all cases, this
brickwork was plastered over and never intended to
be seen. The stripping of plasterwork to expose
internal brickwork is generally unsatisfactory because
of the inferior quality of the brick selected for that
specific purpose, the condition and appearance of the
mortar joints and a frequently lower standard of
overall workmanship. Sometimes however, brick vaults
in basements and internal brickwork in garden
buildings, stables, and out buildings were intended to
be seen and were not rendered but simply limewashed. This is an attractive finish that is practical and
easy to maintain. Wherever possible, limewash finishes
should be maintained or renewed.
GARDEN WALLS
24
BRICK PAVING
Bricks, of appropriate hardness and durability, have a
long history of use for internal flooring, external
paving, and roads. Floor paving with brick is not
uncommon in eighteenth-century cellars, outhouses,
and washhouses.
Decorative brickwork
The term decorative brickwork covers a range of nonstandard brickwork, deliberately detailed to display
colour, light and shade, or textural contrast of all, or
specific parts of, a faade. It was often combined with
raised or recessed configuration of the brickwork
through the skilful use of plain or specifically-shaped
bricks called specials.
Seventeenth and eighteenth-century examples of
decorative brickwork consist of cut-moulded (cut-andrubbed to shape) or purpose-moulded (cast to the
required shape) brick. These special brick shapes are to
be seen in brick plinths, plat bands, cornices, dentil and
string courses, and surrounds to openings. Evidence of
the early use of decorative brickwork can be gleaned
from a study of Jigginstown House where there is use of
cut-and-rubbed features of a buff coloured brick in
25
Polychromatic brickwork
Although the use of multi-coloured brick for
decorative patterning has a long history in England
and continental Europe, most polychromatic
brickwork in Ireland dates from the nineteenth
century as imported coloured bricks became more
widely available. However, Jigginstown House provides
an early example of different coloured bricks, reds and
buffs, used decoratively. In the twentieth century there
was a minor fashion, particularly in the 1940s and 50s,
to use over-burnt and misshapen bricks for decorative
purposes in faades.
26
Stoneware products
Stoneware is a term used to describe a highly vitrified
ceramic that looks superficially like stone. Its unique
appearance derives from its composition of kaolinitic
clay and other minerals. Coade Stone, and other
stoneware products such as those made by Van
Spangen & Powell of London, are essentially forms of
terracotta made from patented recipes. Coade Stone is
made of a proprietary off-white vitreous material, cast
in moulds and fired at high temperatures. From 1767
until around 1840, the Coade factory (initially at Lyme
Regis, but later Lambeth, London) under Eleanor
Coade and her daughter, supplied architectural
ornamentation to builders and architects all over
Britain and Ireland, and further afield. The Coade Stone
factory produced sculpted figures, column cappings,
plaques, medallions, fountains and garden furniture.
There are many surviving examples of Coade Stone
features in Ireland. The ceramic body is quite durable
but, as with terracotta, it can be damaged by the
expansive action of the rusting of iron fixings.
27
28
29
BULGES IN BRICKWORK
There is a range of reasons why bulges may occur in
brick walls, the following is a list of some of the more
typical causes:
> poor original workmanship and defects such as
inadequate cross bonding (can be identified when
the outer wall face is bulging and the inner wall
face remains straight)
> decay of the structure in a variety of ways due to
water penetration, e.g. leading to delamination of
the wall
> rotting bonding timbers
> problems with changing ground conditions
> changes in loading on the wall
> previous inappropriate interventions, such as the
enlargement of openings and the formation of
new openings in a wall without sufficient support
Bulging of a brick wall may be of minor or more
serious concern. Often, the minor movements which
occur throughout the life of structures lead to gentle
bowing which is part of the historic character and
charm of the structure and, in such cases where there
is no concern regarding structural integrity, then the
principle of minimum intervention should be
observed. However, where bulging is found it is
recommended to seek the advice of a structural
engineer with a knowledge and experience of
traditional buildings choosing the right engineer can
often result in less radical, more sensitive and often
cheaper solutions.
Rear extensions, returns, and bay windows, often
built with slender and poorly-bonded piers between
openings, were commonly erected after the main
construction of the building was complete. They were
often built upon shallower foundations, and
consequently the tying-in between later and earlier
brickwork can be compromised and cracks may
appear at the junction.
In chimney construction, the practice of using lime
mortar to line or parge the inner face of flues can
conceal poor bonding of the masonry separating
individual flues on multi-flued chimneys. Expansion
and contraction as a result of years of intermittent
heating and cooling cycles, as well as the aggressive
chemical action of condensing hot gases, leave soluble
sulphates that attack and remove these flue linings,
exposing the bonding problems.
30
REPAIRING CRACKS
Minor cracks can be repaired by carefully cutting out
the affected areas of brick, replacing fractured bricks,
and repointing using a mortar appropriate to the
existing brickwork. Where major cracking has
occurred, or where bricks are displaced or out of
alignment due to structural movement, specific repair
works will need to be planned and directed by a
structural engineer experienced in the repair of
traditional structures.
REPAIR OF CHIMNEYSTACKS
The exposed parts of buildings, such as chimneystacks,
are particularly vulnerable to the effects of severe
weathering and structural failure.
The chimneys found in old buildings are usually
unlined, tall and heavy in construction, and now often
redundant. They may present different problems to
chimneys in modern buildings including leaning,
fractured or loose brickwork caused by movement,
excessive water ingress contributing to frost and
sulphate attack, plant growth, failure of protective
mortar cappings, flaunching and fillets and the loss of
mortar parging to the inner faces of flues.
Erosion of both bricks and mortar joints by the action
of wind, rain (and accompanying frost and sulphate
attack) can seriously weaken a chimneystack. If the
brickwork of the chimney is quarter-bonded, onebrick-thick, reasonably plumb and otherwise
structurally sound, there will usually be enough
support for individual badly-eroded bricks to be
carefully cut out and replaced and the joints
repointed. This may not be possible with a chimney
stack of a single, half-brick width laid in stretcher
bond.
In some instances, a chimneystack may be so out of
plumb, extensively fractured, and with eroding mortar
and loosened masonry that it presents a public safety
issue. It also has the potential to damage other parts
of the building should it collapse. In such
circumstances careful recording, disassembly, and
accurate reconstruction may be the only practical
solution.
31
Brickwork decay
WATER SATURATION
The gutters behind parapet walls are difficult to
access and therefore are often poorly maintained.
Many parapet walls show evidence of having been
reconstructed over the lifetime of the building. This
illustration shows the use of inappropriate
replacement bricks in the repair of the wall
32
ATMOSPHERIC POLLUTION
Brickwork can be affected by chemical attack from
atmospheric pollutants on surfaces that are not
regularly washed clean by rain. These include areas
directly under windowsills and projecting dressings
where there is an accumulation of encrusted dirt.
Where deposits remain on the surface of brick they
can, in time, lead to the formation of destructive salts.
FROST DAMAGE
Different brick types will vary in their ability to
withstand frost damage. Porous bricks will absorb more
water and some may have poorer frost resistance than
denser bricks. It should be noted, however, that there is
no dependable correlation between strength or water
absorption and frost resistance. Frost resistance relates
to the pore structure of the brick. Frost damage results
when the water absorbed by the brick expands on
freezing, breaking the brick apart. Where this occurs it
may be necessary to replace damaged bricks. It is also
essential to discover and remedy the source of the
water that has saturated the bricks and to make good
such defects as leaking rainwater pipes or overflowing
gutters.
SALT CRYSTALLISATION
In historic brickwork, soluble salts present in the
adjacent sub-soil may be carried up a wall by rising
damp. Salts may also be present in the bricks
themselves. The saturation of brickwork can cause the
movement of salts through the wall to the surface of
the brick. If these salts crystallise within the body of
the brick wall they cause sub-florescence. Because the
crystals of salt expand in size, this can result in the
spalling of the faces of the bricks. The white powder
caused by salts crystallising on the surface of the brick
or mortar is known as efflorescence. Efflorescence is
normally harmless, though while it lasts it can be
aesthetically disfiguring. Where it appears, it should be
brushed off and collected as otherwise the salts will
continue to attract moisture and prevent the brick
surface from drying.
SULPHATE ATTACK
Historic brickwork on chimneystacks is subject to
soluble sulphates in condensing gases. These areas are
most susceptible to the harmful effect of sulphate
attack. Sulphate attack can also occur with mortars
based solely on Ordinary Portland Cement (which
contain alite) when they come in contact with soluble
sulphates, such as those that occur in the groundwater
of clay soils. The resultant expansive action can be
seen as a thin linear crack through the bed joints.
WORKING AT A HEIGHT
Carrying out maintenance inspections at a height is hazardous. If you do not feel safe, or are nervous working
at a height, then get professional help with the work.
Using ladders is a major safety issue. Avoid working on roofs or on ladders in windy, wet, or icy weather
conditions. It is always safest not to work alone. You should have someone competent with you to hold the
ladder. Take care of people below when working at a height to avoid injuries caused by falling or thrown
objects. Always use a ladder that is in good condition and of the correct height. Make sure it is secure, angled
correctly with the top resting against a solid surface (not a gutter or a fascia). When climbing ladders make
sure you have both hands free. Always work so you can have one hand on the ladder at all times, have a good
handhold, and do not overreach.
With many buildings that are larger or higher than an average dwelling, it may not be safe for an untrained
person to carry out even the simplest maintenance or repair tasks. In fact, it is not advisable for any untrained
person to work from ladders above one-storey high. If you have a building that is too tall for safe working from
a ladder, you should consider installing a permanent, properly-designed means of access to roof level. Some
works may require planning permission and you should consult your planning authority first. If it is not
possible to provide a permanent means of access to a roof, you could consider hiring, or investing in, a
properly-designed mobile scaffold tower or a mobile elevated working platform.
For further information on the safety issues of inspecting or working on roofs, see the Health & Safety
Authoritys publication: Code of Practice for Safety in Roofwork.
34
4. Repairing Brickwork
This section deals with the options available for the
localised repair of damaged or decayed bricks and the
mortar joints between them. Individual bricks can be
repaired using a specialised technique of mortar or
plastic repair or can be reversed or replaced. The
mortar in the joints between bricks plays an essential
role in the overall performance of the brickwork and in
the visual appearance of a wall. The use of inappropriate
repair materials or repointing techniques is a common
cause of problems with historic brickwork.
35
REVERSING BRICKS
For certain repair works it may be an option to reverse
individual decayed or damaged bricks. In this process,
a damaged brick is carefully cut out and turned
through 180 and re-laid into its original position. The
effectiveness of this repair technique depends on the
soundness of the overall brick. There is little point in
reversing a brick if the new face will deteriorate in the
same way as the original face once exposed to the
weather. Bricks with minor defects may not warrant
being cut out and reversed and, providing there is no
damp ingress or structural concerns, can be left alone.
Reversing bricks requires skill and can be a timeconsuming task. There may also be difficulties in
successfully cleaning mortar off the new face of the
brick.
36
BRICK SLIPS
Brick repair using brick slips (thin tiles of brick) is only
used in very limited situations when it is not possible
to remove the whole brick without causing greater
damage. This repair method is also mainly used for
individual brick repairs and is not recommended for
large sections of repair. The brick slips should match
the existing brick and be a minimum of 25mm (and
preferably 50mm) thick, applied to the clean, even and
pre-wetted surface with a bed of lime mortar to finish
flush with the adjacent brickwork to avoid loosing
historic detail and profile. Brick slip repairs should not
be used on exposed locations such as parapets and
chimney stacks. Thinner, proprietary brick slips which
are intended for use in modern construction (and
frequently seen on brickmakers sample boards) and
are applied with epoxy resins should never be used in
historic building repair.
37
38
39
21/2 x w = d
Step 1
Rake out mortar in joint to 21/2 x width of joint.
Brush out all loose material. Raking out to be
done using manual tools to avoid damage to
the brick arrises
40
Step 2
Pre-wet all surfaces of joint prior to applying mortar
to desired profile (flush profile illustrated)
GAUGED BRICKWORK
Gauged brickwork was and remains a highly
specialised craft that raised the practitioner to the
status of a mason. The special soft-textured rubbing
bricks, or rubbers, which are characteristic of this work
are handcut and shaped to very precise dimensions
and laid with narrow joints in a mortar of lime putty
and fine silica sand.
Specialist advice should be sought on the causes of
failure and appropriate methods of repair from an
acknowledged authority. The repair of gauged
brickwork requires the input of a highly-skilled,
knowledgeable and experienced craftsperson. It is all
too easy to destroy the beauty and accuracy of this
type of brickwork by inappropriate materials and
techniques.
41
Grant aid
Conservation grants are available for the conservation and repair of protected
structures and are administered by the planning authorities. You should contact
the relevant one for guidance on whether the works you are planning are eligible
for a grant and, if so, how to apply. These grants are not available for routine
maintenance works, alterations, or improvements. The type of works must fit within
the schedule of priorities set out by the planning authority. In order for works to
qualify for these grants, they must be carried out in line with good conservation
practice. Repair work following the guidance set out in this booklet should be
considered as satisfying this requirement.
Other bodies also provide grants for building conservation projects. These include
the Heritage Council and the Irish Georgian Society. Their contact details are
included elsewhere in this guide.
Tax incentives are available under Section 482 of the Taxes Consolidation Act 1997
for expenditure incurred on the repair, maintenance, or restoration of certain
buildings or gardens determined to be of significant horticultural, scientific,
historical, architectural, or aesthetic interest. The building or garden must receive a
determination from the Revenue Commissioners who must be satisfied that there
is reasonable public access to the property. Application forms can be obtained
from the Heritage Policy Unit, Department of the Environment, Heritage, and Local
Government.
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43
Cleaning trials
A cleaning trial is essential. This trial will test the
cleaning product and/or technique to determine the
following:
44
Cleaning methods
The cleaning method chosen will depend on several
different factors including the type and condition of
the brickwork, and the type and extent of soiling.
There are three basic cleaning methods for brickwork:
1. Cleaning with water
2. Chemical systems (including poulticing techniques)
3. Abrasive cleaning
CHEMICAL WASHING
When dirt deposits are resistant to water cleaning, it
may be acceptable to use mild detergents and other
surfactants, with or without certain very dilute acids.
Proprietary products containing hydrofluoric acid are
highly corrosive and must always be used with extreme
care, observing all of the manufacturers health and
safety advice. They are often much stronger than
necessary and may be diluted with water several times
below the recommended minimum. Only solutions
with concentrations of below 1% should be used, with
minimum periods of contact with the historic
brickwork. Brick surfaces must be pre-wetted and after
the cleaning material has been on the face of the
brickwork (for typically 2 to 5 minutes) it must be very
thoroughly washed off. Pre-wetting and washing off
should be carried out with a pressure not exceeding
2760 kPa (400-psi).
Test, or trial, patches should always be approved and
judged on their clean and fully dry appearance. Dangers
associated with chemical systems include the formation
of a white bloom on the bricks, resulting from too long
a contact period with hydrofluoric acid, and damage
caused by the careless use of the water lance. Glass,
polished, and painted surfaces in the vicinity should be
carefully protected from damage during cleaning, and
operatives should have full face and hand/skin
protection.
POULTICE CLEANING
Poulticing can be useful for treating specific types of
heavy soiling or stains, especially complex forms such
as oil, grease, or paint. Surfactants, or solvents, are
placed against the face of the brickwork by means of a
proprietary poultice following the manufacturers
instructions. The body of the poultice will usually be
based on either clay or cellulose. After application it is
normally covered with a thin plastic film to prevent it
drying out. Poultice systems can make use of very
dilute cleaning agents without the need to saturate or
abrade the surface. They are normally removed by
hand and by low-pressure water lance. In most cases it
is advisable to approach a specialist to provide a
purpose-made poultice to suit the individual cleaning
requirements for maximum safety and economy.
45
This brickwork shows evidence of damage by overheavy abrasive cleaning which has removed the
fireskin from the bricks making them vulnerable to
accelerated decay exacerbated by the cementitious
pointing
46
ABRASIVE SYSTEMS
SURFACE TREATMENTS
Properly detailed and laid brickwork does not require
any surface coating to improve its weather resistance.
The use of proprietary surface treatments such as
water repellents should be avoided, including those
marketed as being breathable and those promoted as
necessary to repel rainwater from the surface of
external brickwork, to help keep brickwork clean, or as
graffiti barriers. Many such surface treatments can
cause irreversible damage to historic brickwork. The
application of such coatings can actually encourage
problems they can reduce the evaporation of water
from the masonry, trapping water and salts against or
behind the wall surface where they can cause decay.
All proprietary coating materials will ultimately break
down and this is unlikely to occur evenly across a
brickwork faade. The result will be a patchy
appearance and the possibility of the additional
expense, and risk, of having to clean the brickwork to
remove the remainder of the coating.
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48
6. Glossary
AGGREGATE
DIAPER WORK
ANCHOR PLATE
DRESSINGS
ARRIS
EFFLORESCENCE
BED
The underside of a brick
FACING BRICKS
BED JOINT
The horizontal mortar joint between brick courses
BRICK BOND/BONDING
The arrangement of bricks in a pattern so that each
brick binds and bears upon two or more other bricks
below to give strength and stability
CEMENT
A binding material mixed with aggregate and water to
form a mortar or concrete. The term is usually taken to
mean an artificial cement such as Ordinary Portland
Cement
FAENCE
A type of relatively thin terracotta slab, sometimes
glazed, used as a decorative cladding and usually fixed
to the interior or exterior of a building in flat or
moulded panels
FIRESKIN
The vitrified, protective outer layer, formed during the
firing process, on the surface of bricks or terracotta
units
CLAMP
A temporary stack of unfired bricks and fuel, fired to
produce finished bricks
FLAUNCHING
A sloping mortar fillet around the base of a chimney
pot to hold it in place and to throw off rainwater
COPING
A capping or covering to the top of a wall to prevent
water entering the core of the wall
FROG
An indentation in one or both bed faces of a brick
making it easier to handle and to bed in mortar
COURSE
A horizontal layer of bricks together with its bedding
material
GAUGED BRICKWORK
Precisely-sized brickwork laid with fine mortar joints of
pure lime putty and silica sand
HEADER
The exposed end face of a brick
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JOINT
RUBBER
RUSTICATION
MORTAR
SIZE/SIZING
A thin liquid mixture made from a natural adhesive
diluted with water and applied as a sealant or filler
SNAPPED HEADERS
NOGGING
SPALLING
PARAPET
PATENT REVEAL
STRETCHER
PARGING
POZZOLAN
TOOTHING
RENDER
VOUSSOIR
POINTING
REPOINTING
The replacement of mortar in the face joints of
brickwork following either the erosion of the original
mortar or its removal through raking out
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TERRACOTTA
WIRECUT BRICKS
Bricks made by the extrusion of a strip of clay which is
then cut by taut wires to the relevant brick size or
gauge before firing
Useful contacts
The conservation officer in the local authority should be the first person to contact with queries regarding a
historic building. Other useful contacts include:
Architectural Heritage Advisory Unit, Department of the Environment, Heritage and Local Government
Telephone: (01) 888 2000 Web: www.environ.ie
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Further reading
Allen, Geoffrey; Allen, Jim; Elton, Nick; Farey, Michael; Holmes, Stafford; Livesey, Paul and Radonjic, Mileva,
Hydraulic Lime Mortar for Stone, Brick and Block Masonry, Shaftsbury: Donhead Publishing Ltd (2003)
Ashurst, John & Nicola, Practical Building Conservation, Volume 2: Brick Terracotta & Earth, Hampshire: Gower
Technical Press (1988)
Department of the Environment, Heritage and Local Government, Architectural Heritage Protection guidelines for planning authorities, Dublin: Stationery Office (2004)
Holmes, Stafford and Wingate, Michael, Building With Lime, Rugby: Intermediate Technology Publications
(1995, revised 2002)
Keohane, Frank (ed), Period Houses A Conservation Guidance Manual, Dublin: Dublin Civic Trust (2001)
Lynch, Gerard, Brickwork: History, Technology and Practice, Shaftsbury: Donhead Publishing, Volumes 1-2 (1994)
Lynch, Gerard, The Colour Washing and Pencilling of Historic English Brickwork, Journal of Architectural
Conservation Volume 12 No.6, pp 63-80
Lynch, Gerard, Gauged Brickwork A Technical Handbook, 2nd edition, Shaftsbury: Donhead Publishing Ltd
(2007)
Lynch, Gerard, The History of Gauged Brickwork, Conservation, Repair and Modern Application, Oxford: Elsevier
Ltd (2007)
Pava, Sara and Bolton, Jason, Stone, Brick and Mortar, Bray: Wordwell Ltd (2000)
Rynne, Colin, Industrial Ireland 1750-1930 an archaeology, Cork: The Collins Press (2006)
Duncannon Fort, Co. Wexford was partly repaired and rebuilt in Flemish bond brickwork during the eighteenth century
52
advice series
iron
advice series
thatch
advice series
bricks
advice series
roofs
advice series
advice series
windows
maintenance
This guide will help you care for your historic brickwork by
giving advice on:
detecting problems in brick walls
repairing damaged brickwork
repointing historic brickwork
cleaning brickwork
getting the right advice
advice series
bricks