Resisting Rain Penetration with Masonry

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CONTENTS PAGE ... 3

INTRODUCTION SCOPE

3

DESIGN PROCEDURE · ASSESS AND SELECT

4

ASSESSING EXPOSURE FOR SPECIFIC LOCATIONS

.... 4

SELECTION OFMATERIALS AND CONSTRUCTION TO RESIST WIND·DRIVEN RAIN 1

TYpe of brick

2 3

Mortar composition

4

5 6 7 8 9 10

.

.

6

7

.

................................ ........................ 7

Thickness of leaf Cavity walls Width of air space within any cavity Mortar joint, profile and finish .

..

.

8 8 8 9

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Cavity insulation "'

Architect ural feature s and local practice Applied external surface finishe s Quality of workmanship to be achieved on site

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10

.. 12 ...... ......... ........................... .. 13

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DAMP PROOF COURSES AND CAVITY TRAYS ...............14

General

Perfonnance [unctions

.......... 14

.

... 15 ... 15

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Continu ity and support Resisting rising damp Immediately above ground level Below ground level

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................................................................ 15 .. 15

.......

.

Controlling downward movement of wat er

Cavity walls Over openings Arches Stop ends Weepholes

.... 16 . 16 .. .. ..

16

.... 17 ..

17

Requirements for damp proof cou rses and cavity trays for specific parts of buildings

At jambs to openings .. Sills .. Requiremen ts for additional cavity trayswith cavity insulation External wall becoming an internal wall .. Parapets Copings a nd ca ppings Chimneys Structural frames

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Flashings and weat herings

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19 19 20 .. 20 21 22 22

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23

CONCLUSION

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REFERENCES

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ACKNOWLEDGEMENTS TABLES Table 1 Table 2 Table 3 Table 4

Classification of exposureto local wind·driven rain ,

.

Minimum thickness of solid brickwork walls, with and without rendering, to resistrain penetration in various categories of exposure.. Thermalinsulation materials forusein cavity insulated walls Summary of materialsusedfordamp proofcourses and cavity trays

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5 7 10

.......... 15

INTRODUCTION

Brickwork has bee n a dependable form of construction for weather resistant walls for

hundreds of years, but conventional bricks and mortars are not themselves waterproof. Moisture may penetrate brickwork by diffusing through microscopic voids in the materials, or by

percolating or flowing into and through hairline or more noticeable cracks in the fabric. The effectiveness of a solid brick wall in resisting penetration by wind-driven rain is in direct

proportion to wall thickness. Traditio nally, for buildings in locationswhere greater severity of

exposureto wind-driven rain is experienced. thicker walls are used compared with those for buildings in more sheltered situations. In the mid-nineteenth century there was

considerableinterest in the construction of low-cost housingforworkers. Economy of material was sought, but thinner walls equated with reduced

resistance to rain penetration. This shortcoming of solid walls led to expe rime ntation with hollow wall construction by the use of part icular bo nding arrangements such as rat-trap bond, Silverlock bond and Dearne's bond and also by the development of patent hollow bricks. However, the most significant development was the introduction of double-leaf cavity walling. By the twent ieth century this technique had becom e esta blished and by th e' 930's it was widely used in housing. The design of the cavity wall accepts that solid masonry subjected to wind-driven rain will not be absol ute ly waterproof but is capab le of providing substantial resistance to penetration. To divert the passage of any moisture that may pass throug h the externa lleaf of the wall the cavity is introduced to drain it down and out again to the exterior. This ensures that water willnot penetrateto the intern al leaf of the wall causing dam p cond itions within the building.

SCOPE The resistance of masonry to wind-dnven rain involves assess ing performance relative to anticipated exposure, as opposed to achieving an absolute condition of its being waterproof. This publication examines and comments on the relative significance of the various factors that need to be consideredwhen assessing exposure and then specifying an appropriate wall construction for any pa rticular application. Solid brick wallconstruction is considered and also the protection offered by rendered finishes is acknowledged, but the publication concentrates on the deta il design and s pecificat ion of cavtty walling

with an outer-leaf of fairface brickwork. The effects of incorporating thermal insulating materials within the cavity are also examined.

As damp proof courses and cavity trays are essential components in correctly detailed cavity wall design, guidance is included on their specification and installation. With an und erstan ding of the constra ints a nd opportunities that attend differences in severityof exposure and in the performance of diverse construction features, a designer can exploit the great choice offered by brickwork to provide effective protection and attractive appearance.

DESIGN PROCEDURE - ASSESS AND SELECT

Because the performa nce of a specific form of wall constructionhasbeen satisfactory in a particular locality it must not be assumed that it will be equally suitable in other regions. Design and specification assuming worst caseconditionsmay

be considered to provide notionaluniversal applications, but for the majority of buildings on the majority of sites such a basis for the cho ice of construction would be un justifiably restricted and

lead to unwarranted expense. The acknow ledged procedure is to assess the

severity of exposure that is experienced at the location of the proposed building and then select and specify a construction to provide the appropriate resistance to rainpenetration. folloWing this meth odical approach a

construction that has relatively low resistance to rain penetration may be quiteacceptable in a

Location. site factorsandbuildingdesign can increase the anticipatedseverity01

sheltered locatio n, but be who lly inappropriate where more severe conditions areanticipated.

exposure, but even so, well considered

cavitywall construction can be effective

ASSESSING EXPOSURE FOR SPECIFIC LOCATIONS

Assessmentof exposure to wind-driven rain should be regarded as a necessary and worthwhile

windspeeds recorded at various meteorological

first step in the des ign proced ure. When determining the likely expos ure of a building, the most exposed part shou ld be given particular

used in calculationsto determine driving rain

attention and this may affect decisions concerning

the widevariation of exposureto wind-driven rain

the choice of design and materials for the whole of the building.

experienced nationally, but it was of limited

Having determined the level of risk likely to be experienced the designer, using the guidance on

resistance to rain penetrationof differe nt formsof construction and the factors affecting rain resistance described in this Design Note, should select the materials and form of construction that together will provide adequate performance, paying due regard to the importance of correct detailing and appropriate standards of workma nship .

stations throug hout the United Kingdom could be indices relative to the geogra phical locatio ns of proposed building sites. This meth od demonstra ted

practical value because of the rather generalised nature of the dataand the assessment method. Collection of data continued in the 1970's and1980's and with the benefit of computer analysts the Meteorological Office was able to produce improved data, based on the ob serva tion that prolonged rainfall was usually associated with

stronger thanaverage winds.

In 1976 the Building Research Establishment Report Driving Rain Indez.' 1proposed a method of assessing the quantity of rain falling on a vertical

A more refined and rea listic method of prediction was eventually develop ed and published by the British Stan da rds Institution as BS8104 Bri tish Standard Code of practice for Assessing exposure of walls to wind-driven rairP I. lt allows

surface such as a wall. Annualrainfall and average

calculationsof driving rainfall for different

orientations. It alsoallows annualaverage values to

be calculated as well as quantities forthe worst likely spellin any three year penod. Rainfall varies considerably across the country but is largely unaffected by local features. Conversely, the general wind speed does not change much across the country but It is affected

Table 1 gives exposure categories defined in

terms of woll spell indices calculated using the locol spell index method specified in BS 8104. The indices, denved as they are from inherently variable meteorological data, should not be regarded as precise. Where assessment produces an index near

the borderlinethe designer should decide which is the most appropliate category forthe particular

significantly by local features such as the spacing and height of neighbouling trees and buildings and whether the ground is flat or rises steeply.

case, using local knowledge and experience.

BS B104 permits corrections to be made for ground terrain, topography,local shelter, and the

Table 1 is based on the 4 exposure zone series

form of the building concerned. These factorscan

defined in BRE Report BR 262 Thermal insulation: avoiding risksl31, which simplifies the 6 category series specified in Table 10 of BS 5628 : Part 3

have a major effect on the calculations and it is

British Standard Code of practice for the use of

important to recognise that , because of their influence,within any geographical locality

masonry : Materials and components, design and workmanship4J. As can be seen in Table 1

considerable variation of exposure can be expected

there are no overlaps in the definition of the 4

from site to site.

categories. Considerable overlaps in the definitions

BS 8104 gives recommendations for two methods of assessing exposure of walls in buildings to wind-driven rain, namely the local spell index

method and the locol onnuol index method. The locol spell Index method should be used when assessing the resistance of a wall to rain penetration. The locol onnuol index is intended for usewhen considering the average moisture content of exposed building material or when assessing durability, weathering and likely growth of mosses and lichens.

of the 6 category series caused some confusion and uncertainty of interpretation. TheBR 262 series is thereforegenerally considered to be an

improvement on the BS 5628 : Part 3 selies. BR 262 provides a simple procedure for assessing exposure to wind-driven rain forwalls up

to 12 m high. It is plimalily intended for low rise domestic buildings but may also be considered suitable forother categories of buildings of similar scale.

The simplified guidance is based on a map which defines zones in which similar exposure

conditions are predicted. The predictions are based on calculations in accordance with BS 8104. The

Categoryof Exposure »

Colculated quantity of wind·

zones are numbered 1 to 4 and correspond with

driven rain·

categolies Sheltered to Very Severe as noted in Table 1.

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The calculations defining the mapped zones in Sheltered

Less than 33

BR 262 assume "worst case" conditions and so

2

Moderate

33 to less than 56.5

provide very conservative guidance. Using the BR 262 map to predict exposure restlicts the choice of

3

5evere

56.5 to less than 100

construction becauseit is not able to identify sites

4

Very severe

More than 100

within each zone which may benefitfrom shelter that considerably reduces exposure to wind-driven rain. Greater choice of construction is justified by

• Based an exposure zones defined in BRE Report BR 262

the more specific assessment possibleby fcllowing the B5 8104 method.

• Maximum wall spell indexcalculated usIng the /oca/ spell Index methodspecifiedinBS 8104

Tolile

Classification of exposure to localwind-driven rain

SELECTION OF MATERIALS AND CONSTRUCTION TO RESIST WIND-DRIVEN RAIN

The following factors affect the resista nce of b rickwor k walls to wind·driven rain. The order of th e listing does not indicate relative importance. Each

driving rai n will be ab sorbed into th e bricks . If the duration of the rainfall is short this behaviour may

factor must also be considered in relation to other

the water reaching the mortar joints. However, when the surface of the mate rial approaches

funct ions of the wa ll such as st rength, dura bility,

be conside red beneficial because it prevents mo st of

sound and thermal insulation:

saturation point water tendsto run more readily

• type of brick

down the surface and, as in wallsof dense units,

may penetrate via paths at the mortar joints. In

• mortar composition

very severeand prolonged conditions of driving rain

• thicknessof leaf • presenceof a cavity • width of airspace within any cavity

ceases long before such complete saturation and

• mortar jointprofile and finish • presence, type and thickness of any cavity insulation • architectural features and local practice

• presence of applied external surface finishes • quality of workmanship to be achieved on site

Detailed considerations 1 7'fpe of brick Brick ty pes vary considerably in their physical properties, bu t when specifying brickwork with

regard to resistance to wind-driven rain no distinctionis made between them. In a wa ll constructed of dense bricks, with low

water absorption characteristics (for example those of the Enginee ring Classes), on ly a relatively sm all qu a ntity of water will be absorbed into the bricks. The greater proportion of a ny rainwa te r falling on to th e wa ll will ru n down its face a nd may be blow n into a nd th rough it via paths in the mortar joints,

particularly at the interfaces between the mortar and the bricks (see 6 below). In contrast, in a wa ll of bricks havi ng relativel y

high water absorption characteristics, such as many han dmade and stock bricks, much of th e water runningoverthe wall surface in conditions of

ABSORBENT

water may be abs orbed further into t he brick s and eventually reach their inner surface, first as dampness and then as free water. Generally rain

DENSE

water is evaporated from the wall by the drying

effect of wind and air movement. These two modes of action are sometimes

referred to as the raincoat effect, in the case of dense, low absorption units, and the overcoat effect, in th e case of high a bso rption units . Solid wa lling can ultim ately be pen etrated by pro longed exposureto wind-drive n rain regardless of the water absorption characteristics of the bricks . Altho ugh water a bso rpti on va ries greatly between different bricks, this property has only a relatively small influe nce on the resistance of the

finished wall to wind-driven rain. In persistent conditions of wind-driven rain waterwill penetrate masonry leafs th rou gh the m ort ar joints regardl ess of the b rick type.

Nodifference is detectable between the rain resista nce of brickwork built of the va rious forms of brick unit, ie. so lid, frogged or perfo rated . There

have been anxieties expressed that walls built of perforated bricks m ight be less resist an t to wind· drive n rain tha n those built with solid or frogged ones, bu t such fea rs a re unfou nded.

A report on UK experience in the use of pe rforated bricks, BRE Digest 273 Perforated clay bricks'S), points out th a t mo st of them a re m ad e with bodies of low water abs orbe ncy an d th at , with

regard to rain penetration, there is no evidence of any significant difference in performance between solid a nd perfo rated br icks with equiv alent low

porosity bodies. It also comments that there is no evide nce to support the suggestion th a t

perforations may act as reservoirs in which rainwa te r collects dun ng rainy pe riod s, subsequently giving rise to pro blems such as

efflorescence or frost attack. the "OVERCOAT" effect

the " RAINCOAT" effect

Designation ( i ) and ( ii It e.g. 1:0-1J.. a nd 1 :'4 : 41/; ceme nt : lime: san d respectively, being the least perm eabl e. These m ortar Designati ons are often used in conjunctio n with den se, low wa ter abso rption fired clay b ricks. This combination is satisfacto ry but sho uld not be regarded as providing

Of th e various mixes s pecified for the mortars of each Design ation those incorpor ating lime in th eir composi tion show a n improvement in bond development an d, as a consequ en ce, a bett er resistance to rain penetration th an those morta rs based on air entrainme nt a nd /or mineral m aterials other tha n lime. Howeve r, althoug h this advantage is detectable, it is no t significa nt enough to justify limiting the application of any particular type of mix.

a waterp roof. or near waterproof, co nstruc tion (see 6 below).

3 Thickness of leaf

2 M ortar composition Mortars vary in water permeability relative to their cem ent content, high strength mortars of

.

Solid wall construction of brickwork, in commo n with ot her forms of ma sonry, gets wet when subjected to ra in and absorbs so me of the wa ter, but when the rain sto ps it dries out again losing the moisture to the air by eva poration, an action which

Strong den se Design ation ( i ) mort ar is no t

suitable for use with calc ium silicate bricks and se lection is governed by other facto rs such as accom mo dati on of movem en t, durab ility and stre ngth. Design ation ( iii ) an d ( iv I mo rtars are often mo re appropriate for th ese bricks, eg 1:1:6

is often accelerated by wind .

and' :2:9 cement : lime: sand.

The resista nce to rain pen etrati on of a solid wall is th erefore dep endent upon its thickness a nd this is reflected in tra ditional const ructlcn - th in walls are

For alternative mortar ty pes and mixes of Designations (i) to (iv) see Table 15 of BS 5628 : Part 3. The ta ble lists various mixes for ceme nt, lime and sa nd m ort ars, masonry ceme nt and sa nd mortars, and mort ars of ce me nt and sa nd with the addition of air-entra ining addi tives.

used in very shelte red location s an d th ick ones wh ere exposure is greate r. Table 2 sho ws the recomm en ded minimum thickn esses for both ren dered and unrendered solid wa lls for va rious categories of expos ure.

Maximum recommended category of exposure rsee "'bI' Thickness

Unrendered

Rendered

Extemally insulated

Impervious Cladding

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of brickwork(mm)

90 2'5

not recommended _"-51

not recommended

61

328

440

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2

betwee n the internal surface of the masonry and any intem al lining.

NaTE5: Walls of half-brick thickness are Widely used for do mestic garages and garden sto res, but they may be penetrated by persistent driving rain.

NaTE2: Rendering should comply with BS5262.

NarE 6: Historically 215 mm thick unrendered brick

NaTE 1: A notional cavity should be provided

NarE 3: External insulation should have a Technical

Approval for use on solid walls subjected to Exposure Category 3.

walls are commonly found performing satisfactorily in z-sto rev houses in towns and cities in the UK. Such locations are generally very sheltered where local spel1 indices are of 20 11m 2 or less .

NaTE4: Examples of typical impervious cladding syste ms are noted in 9 below. nib e 2:

Minimum thickness ofsolid brickwork walls, with and without rendering. to resist rain penetration in various categories 01 exposure (Based onTable 11 inBS 5628: Part31

Typical section of cavity wall Typical section of cavity w all at opening

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4 Cavity walls

Table 2 does not apply to cavity construction. In cavitywallsit is accepted that some water will inevitablypenetrate the outer leaf in prolonged periods of wind·driven rain, but proper design and positioning of damp·proofcourses and trays and of any insulation will minimise the risk of penetration

further into the building. Where the cavity is unavoidably bridged, e.g. at window and door openings, correct detailing is essential. Cavity wallswith a half-brick thick outer leaf (90mm minimum)can performacceptably in all categories ofexposure listedin table 1. Nevertheless, a designer mayconsider theuse of a thicker outer

leafto reduce the quantityofwaterreaching the cavity. No relia nce should be placedon the inner leafof a cavitywall to resist water penetration.

5 Width of air space within any cavity In cavity walls the space between the two leaves

For all practical purposes brickwork can be effectively jointed with the mortars conventionally used in traditional and modernconstruction, but the jointsshould not be considered waterproof. The brickto mortar interfaces in the wall are the positions most vulnerable to rain penetration. A

microscopiclabyrinth of voids exists at the interface because of the physical nature of mortar bonding. The interface is also a likely location for capillary cracks dueto imperfect adhesionbetween a mortar

and bricks. Good adhesion is difficult to achieve with absolute consistency and the interfacemay be degraded further by crackingdue to moisture and thermal movements subsequent to construction. The toolinginvolved in finishing joints such as those with bucket handled and struckweathered profiles firms the mortar, reducing its permeability at the surface, and pushes it tight to the bricks, thereby improving its adhesion to them. Both

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of masonry is intended to prevent any water from passing from the outerleaf to the inner one. In most

situations a cavitywallwith a half-brick thick outer leaf (90mm minimum), a SOmm cavity and an inner

leaf is satisfactory. In conditions ofmore severe exposure considerationshould begiven to theuse of wider cavities.

6 Mortar joint, profile and finish

Regardless of the type of brick or the mortar composition, it is essential to fill completely all bed joints andcross joints (sometimes referred to as

"perps" or "perpends") to minimise the risk of rain penetration. Workmanship is very importantin this regard , see 10 below.

characteristics improve the joints' resistanceto

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penetration by water. Recessed joint

profiles form ledges which impede the run-off of water and encourage it to enter the walling at the mortarI brick interfaces. Recessed joint profiles formed by rakingout the mortarwithout subsequent tooling to firmits surface further increases the vulnerability of the

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wall to rain penetration. Recessed joints also reduce

the width of the mortar joints. Compared with bucket handled and struck weathered profiles, the risk of rain penetration is greaterwith recessed

joints and so they s hould only be used in Sheltered exposurecategory locationswhen resistance to rain penetration is important.

Bucket Handle

Struck Weathered

Flush

Recess ed

Mortar joint profiles

7 Cavity insulation

Thermal insulation materials may be effectively installed within the cavity of a cavity wall to increase its overall resistance to thermal tra nsmittance, there by redu cing heat loss from the building. But if the insulation is not installed correctly, or without due care, its presencecan constitute an increased risk of rain penetration of

the wall tsee Thermal insulation: avoiding risk9' 11.

Some insulation materials are built-in so that a

Some thermal insulation materials, egoinjected

foamed urea forma lde hyde . are subject to restrictions of their use vis-a-vis severity of

exposure. All thermal insulation materials s hould be specified a nd installed in acco rdance with the relevant British Standa rds, Technical Approvals and the manufacturer's instructions. The inclusion of insulation materials in a cavity wall sometimes requires the installation of

add itional cavity trays (see page 19).

free airspace is retained, Le. a partial'fill system. The

retained air space should be a minimum target width of 50 mm. Inner leafconstruction of face

_Intem.r brick or block

insulated blocks require a retained air space.

In a full·fill system the cavity space between the inner and outer masonry leaves is filled wit h insulation material either

by

building it in as construction proceeds

or by injecting or blowing it into the cavity after the wall has been comp leted . The cavity space s hould be a minimum target width of 50 mm , but the risk of rain penetrationwill be reduced if a wider cavity is used, Thermal insulation materials are provided in a

form specifically inte nded for a particular insta llation method. Products for partial ·fill applications shou ld not be used for full·fill ones, an d vice versa. Only products specifically manufactu red for insulating masonry cavity walls should be used; other forms of insulation material must neverbe

substituted. A su mmary of the ty pes of materials appropriate for use in partial-fill a nd full-fill cavity

Cavity wall with partial-fill cavity insulation

wall insulation systems is given in Table 3.

Cavity wall with full-fill cavity insulation

8 Architecturalfeatures and lacalpractice British Standard

Product ..... ; ..

Partial-Fill Cavity Insulatian

Mineralfibreslabs

Examples of features that cause concentrated wetting are:

Foamedglass slabs Expanded polystyrenebead board Extrudedexpanded polystyrene board

Architectural featu reshavean important affect the risk of rain penetraticn. Thedesigner shauld always cansider whether the destgn details will increase the tendencyfor the masonry to be wetted mare than it wauId be by incident rainfall alone. an

3837 : Part 1 Specification ~

3837 : Port 2 Specification

Rigid polyurethane (PUR) board

4841 ' Part , Specification

Polyisocyanurare (P1R) board

4841 : Part, Specification

a) An area of glazing or imperviouscladding can produce a large amount of surface water run -off and unless there is a gutter to collect it, or a projecting sillto throw it clear, excessivewetting and possible waterpenetration can occurin any masanry below

Futl-Fill CavityInsulation UTTS to U 811U.TIN

Mineralfibre bolts

6676 Part 1 Specification 6676

Part 2 Installation

LOOSEMAnxtAL TOU .. toWN IN

Mineralfibre

Polystyrene beads

Polystyrene granules

tNT£CfU) FOAM£D nASf1C

Ureaformaldehyde (UF) foam

5617 Specification 5618 Installation

Polyurethane (PUR} foam

7456 Instal/ation

(/or stabilization and insulation

7457 Sped{icotion

of Cavity walls)

mble 3

Thennal insulation materials for use in cavity

insulated walls

b}

Because of its profile a recessed bandcoursecan cause local concentration of wetting. Corresponding intrusions intothe cavity dueto the setting back of bricks ar ather masanry units to farm the feature may increase the riskof water crossingthe cavity, The use of reduced width unitsto form the recesswould avoid intrusion inta the cavity Alternatively, the introduction of a cavity tray immediatelyabave the set-back may be considered.

Thedegree af welting of masanry can be reduced by ensuring that rainwater is thrown clear of the walls by adequate averhangs and drips ar by providing drainage to takewater away from the masonry,

Append ix E of BS 8104 contains a deta iled com mentary on the protection afforded by projecting features such as sills, copings, string courses, roof eaves andverges. It explainswhy

small overhangs areso effective in protecting walls. It might be anticipated that water dripping from a projection would quickly be blown onto the wall a short distance below. However, airclose to the wall forms an almost still boundary layer and to the exte nt that it moves at all, it flows parallel to the surface. Because of this drop lets falling from projections tend to fall vertically down to the ground . In general the Appendix corroborates the beneficial effects tra ditionally asc ribed to projecting

features, but it also reports on studies which

indicate that in some conditionsof high winds an overhang at the top of a wall ca n lead to greater welli ng when com pared with a flush topped wall. These findings are embodied in the allowances relating to gable ends and eaves to pitched and flat roofs in the BS 8104 method for assessing exposure to winddriven rain. The Appendix also reports on the effect of surface texture and also the concentration by wind of surface waterrun-offat external and internal corners of buildings. The designer should always take account of local knowledge, experie nce and the evidence of local traditio nal forms of cons tru ction and building detail. The fact that some building design features

are not characteristic of a particular area orregion may indicate their unsuitability for the rigours of

local exposure.

Unsightly patchiness due to differences in wetness caused bythe application 01 water repellent treatmentto brickwork at parapet level

9 Applied external surface finishes Forboth smgle-leafand cavity walls, total resistanceto rain penetration can be achieved only by the use of impervious cladding systems . lYpically such systems are panels, boards or sheeting of metal, plastics or timber with weatherproof joints, and overlapping slates, shingles. or tiles. As indicated in Table 2 rendering can substantially enhance the rain resistance of brickworkwalls. It may be applied to solid walls and to cavity walls. It is essential, however, to select the right type of mortar mix , the thickness and number of coats and to deta ilthe wall correctly in order to minimise shrinkage cracking, which may otherwise reduce the effectiveness of the rendering. The recommendations of BS 5262 British Standard Code of practice for external rendered finisheiJ6} and BCA publication Appearance matters - 2 : External rendering71should be followed . The combination of full-fill insulation and rendering inhibitsthe drying out of any moisture that may enter the outer leaf of masonry. The moisture contentof the outerleafmay consequently rise increasing the risks of frost action of the maso nry and sulfate attack of the jointing and rendering mortars. Claybricks of durability designations ML or MN las specified in BS 3921 British Standard Specification for Clay brickiJ 8I1

arenot recommended for such wallsin locations exposed to Severe or Very Severe categories of exposure to wind-driven rain. FL or FN clay bricks may be used.

In all categories of exposurewhereFN or MN clay bricks are to be used behind rendering the jointing and render undercoat mortars should be made with Sulfate Resisting Portland Cement ISRPCI. The use of masonry paint systems (see BS 6150 British Standard Code of practice for painting of buildingiJ911 and other proprietary external finishes

including colourless treatments, e.g. silicone-based water repellents (see BS 6477 British Standard Specification for water repellents for masonry surfaceg. 10Il, may increasethe resistance to rain

penetration. However. they may also reduce the rate of evaporation of any water from the wall and so the moisture content of the wall can increase if water gets behind the paint or surface treatment eitherby penetrating imperfections in it or entering from adjoining construction. In some cases this has lead to localisedwater penetration and/or saturation of the brickworksufftcient to cause frost damage to clay bricks of ML and MN durability designation in winter conditions. Water repellent surface treatments arenot generally recommended for clay brickwork. Traditionally brickwork that is correctly specified and constructed is durable, withstand s weathering and resists the penetration of wind-driven rain without the needof waterrepellent treatments. They should not be applied to clay brickwork without the approval of the manufacturer of the bricks specified.

"'Tipping andtailing" generall y produces cross

joints with poorreslst ance te fain penetration

severe and Very Severe categories of exposure, most periods of wind-driven rain are interrupted by a drying period beforethe bricks in the wall have become so saturated that the rain passes through . By contrastrain falling on a wallof low water absorption bricks(raincoat effect) will run down overtheirglass-like surfaces to enter immediately any imperfections in the jointing.

10 Quality of workmanship to be achieved on site

The quality of workmanship actually achieved, both when constructing masonry and when installing any insulation material, is the most important factor affecting resistance to rain penetration, All workmanship should be in accordance with BS 8000 : Part 3 British Standard for workmanship on building sites : Code of practice for masonry " l. Detailed guidance on workmanship is also given in BOA Building Note 1 Brickwork " Good site practice ' ' I. Some brickwork requires particular care in its

construction compared with others. For example, considerclay bricks of low waterabsorption and those of high water absorption. It has been stated that allmortar joints should always be filled (see6 above), but from the description of the raincoat effectand the overcoateffect (see 1 above) it will be evident that minor imperfections in the jointing of

high water absorption bricks (overcoat effect) will not always be critical. This is because. except in

The importance of filling all mortar joints to ensure good resistance to rain penetration cannot be overstated, but the cross-joints ("perps") are often not filled properly because they are formed using a poortechnique known as "tipping and tailing". Small dabs of mortar are Wiped on the leading and trailing edges of the end of each brickwhen laying. This bad practice leads to cross-joints that are not adequately filled and therefore do not have the best resistance to rain penetration. Any anticipation that the joints willsubsequently be filled by mortar flowing down into them from the next layer of bedding mortar is fallacious. Filling cross-joints by this means is imposs ible. Stretcherbonded walls have sixty cross-joints per square metre and so if they are poorly filled the shortcoming can be significant. Filling cross-joints properly by applyinga fulllayer of mortar to the end of each brick is not difficult or time consuming. It is regarded as good practice and therefore it is not unreasonableto insist that it is done.

- Buttering- the end of a brickwith mortargives 8 fully fill ed cross joint

DAMP PROOF COURSES AND CAVITY TRAYS Genera l Adamp-proof course(dpc) in a building is intendedto provide a barrierto the passage of water from the exterior of the building to the interior, or from theground to thestructure, or from

one part of the structure to another.

Where the dpc is intendedto prevent the upward movement of water due to capillary action throughmasonrymaterials continuity is important although, in normal circumstances, no hydrostatic pressureis involved. loints shouldbe made in accordance with the instructions of the manufacturer of the dpc material used. Where no specific instructions are given, the dpc shouldbe lapped a minimum 100 mm orthewidth of the masonry leafat comersorintersections. Penetration ofdpc's and cavitytrays by services, reinforcement, fixings, etc. shouldbe avoided as far as possible. Where they have to pass throughcare shouldbe taken to form the necessary holeneatly and carefully seal around the breach. Where water is subjected to hydrostatic pressure, or ismoving in a downwards direction

under the Influence ofgravity, any jointsInthe dpc shouldbe made waterproof by lapping and sealing following the dpc manufacturer's specification for sealant or adhesive. Opc's shouldextend throughthe full thickness ofa wall or leaf, and to the externalface whereit shouldbe clearly visible. Adpc shouldnot be bridged by pointing, rendering, plastering, wall tiling, etc. To prevent penetrationofwater beneath the dpc,whichcan occurIfit Is placed directly on an irregular bed surface, and to producea good bond to resistsubsequentmovement, dpc's shouldbe laid on a smoothbed offresh mortar. The use of coarseaggregates for the mortar shouldbe avoided as they mightdamage the dpc. Sometimes dpc's are Installed to form a slipplane to accommodate differential sliding movements betweenadjacent parts of the building structure; Insuch a case the mortar bed shouldbe trowelled smooth, allowed to set, and then cleaned offbefore the dpc is laid. Alternatively, a doublelayerofappropriate sheet dpc material with no mortar or adhesive between them may be specified.

itoo ve

Ope's should be sandwiched betwee n mortar

Performance To ensure adequate performance, dpc's and cavitytrays should have the following material properties:

an expectedlife at least equal to that of the building (b) resistance to compression without extrusion (c) resistance to sliding wherenecessary (d) adhesionto units and mortar wherenecessary (e) resista nce to accidental damageduring Installation and subsequent building operations 10 workability at temperatures normally encountered duringbuildingoperations, with particular regard to forming and sealing joints, fabricating junctions, steps and stop ends, and the ability to retainshape (a)

table 4 gives Information on performance of Individual materialscurrently used fordpc's. BSB215 British StandardCode of practice for des/gn and installation of damp-proofcourses in masonry construction " )gives guidance on the

basic principles concerning dpc's, their function and their Installation Inmasonry. Itcontains recommendations for the selection, designand Installation ofdpc's Inboth solid and cavity construction.

Material

Limitations or benefitsin use

Resistant to extrusion : Ease ofiointing ..... ~~~~'.~iii~l~ .ad

..:.

Rigid Materials OA r DI'C MICKS complying with as 392 1

.t

SUitable against rising moisture only

SLAn comptying with as 743

.t

Suitableagainst riSing moisture only.

Goodperformance in resisting flexural stress.

Semi-Rigid Materials MASTIC AsnlALT

nf a

X

complying with 85 6925 or 6577

:

..... .. . .. ... .

..... .;

.

Flexible Materials UADSH£ET

Requires protective coatingagainst

comptying with as 1178

corrosion when setIn mortor > 25mm.

Requires protective coatingto avoId staining masonry.

COP1'EJt SHEET

compTying with C 104 or C 106 ofBS2870 MTUMEN SHEET

compTying withas 6398 - withHessian base(class A) - withFibre base(class B) . wtth Hessian base andlead (Class DJ . withFibre baseand lead (class E) LOW DENSlTF 1'OLrETHnENI! SHEET

complying with as6515

Difficult to handleIn cold weather Difftcultto handlein cold weather. Di/flcultto handleIn cold weather Difftcultto handleIn cold weather

~ ~ ~ ~

Poor bond performance. Norrecommended tor use In conditions offlexural stress.

'"

Goodbondingperformance with mortar. rrTCH I"OLYMElI SHUT

laDle 4

Summary of materialsused for damp proof courses and cavity trays

Junct ions

Resisting rising damp

Dpc and cavity tray detailscan be simple and straight forward in straight plainwalls, but at

Immediately abovegroundlevel

corners, junctions, returns, curves, changes in level,

changes in plane, around openings, etc., the need forcontinuity oftenrequires quite complicated installation of dpc material. During the preparation ofdetail design and specification for a building careful consideration should be given to these positions and detailedthree-dtmensto nal drawings made ofall dpc's and trays at junctions, steps, angles and stop ends. Many common details cannot be formed satisfactorily In-situ, unless they are fabricated in lead. If materialsother than lead are to be used in complex situations, then pre-formed cloaks should be specified, so as to restrict the site operation to simple jointing.

Continuity and support Where practicable, dpc's and cavitytrays should be formed Ina continuouslength of material to minimise the need for joints. Cavity trays should be supported at their joint positions to facilitate effective sealing. Continuous support is advantageous as it avoids sagging and deformation.

In everyexternalwall, a dpc shouldbe provided at least 150 mm abovethe finished level of the external groundor paving. To preventthe transfer of moisture from external wallsinto solidfloors, the damp'proof membrane in the floor, and the dpc in the wall, should overlap a minimum of 100 mm or be sealed. In cavity workthe cavity should be filled to ground level with fine concrete, and weepholes should be left In the vertical cross jointsof the outer leaf, at intervals not greater than 1 m, immediately abovethe top of this fill. The purpose of the fill is to prevent the leaves of the cavity wall beingdisplaced into the cavity by pressurefrom the groundduring backfill operations orsubsequent loading ofthe ground.

Belowgroundlevel Horizontal and vertical dpc's are required where the lowestfloor of the buildings is belowground level. Inthis situation it may be necessaryto considertanking (seeas 8102 Bri dsh Standard Code of pracdce for

protection of structur es

against water fr om the groun d 14 ) ).

._--.-_

... .....,."-'r'

Pre-formed cavity tray for anarch

Stop ends fmedto discontinuous cavity tray

Controlling down word movement of woter Cavity walls The design and specification of a cavity wall

should be based on the ass umption that, in conditions of persistent driving rain, water will penetrate the outerleaf and run down its inner

surface within the cavity, Wherethe cavity is bridged, egoby lintels, structural beams, floor slabs, pipes, and ducts, dpc's in the form of cavity trays, with stop ends and weepholes, should be provided

Arches The curved form of an arch makes the use of a normal cavity tray impossible. A conventional cavity

tray can be installed in the bed joint immediately above the crown of an arch and for a minor segmental arch in a relatively sheltered location this may be considered acceptable. The tray should extend beyond the width of the arch and be filled with stop ends. To improvethe construction short

lengths of flexible sheet dpc material can beset around

to divert water out again.

the curve of the arch in an overlapping arrangement.

Over openings

use a pre-formed arch tray (see figure above). Depending on the detail design of the opening the

A simpler and more reliable construction is to

In cavity walls, cavity trays should be provided over all openings(including small openings for

tray may be installed at the intrados or the extrados,

ducts, services, etc), unless they arewell protected

i.e. under or over the arch ring.

by a roof or balcony overhang. The cavity tray should step down or slope across the cavity not less than 150 mm towards the external leaf and, preferably, terminate in a small drip on the face of the wall.

The cavity tray over an opening should overlap the vertical dpc's at the jambs to ensure continuity of damp'proof measures (see figure on page' 8)

A pre-formed tray should incorporate stop ends and, becausethe arch form inevitably drains any penetrating water to its bearings, care

should be taken to ensure effective weepholesare

provided.

In this building there is a cavity tray in the

fifth course above thesoldier course. Note the weepholesatthislevel- open crossjointsat 900mm intervals

'Right

Stopends

A proprietaryplastic wind baffleinsert to form a weephole

Weepholes

Where trays are discontinuous, andin a position

that is not well protected by a roofor balcony overhang, stop ends should be filledat or near the ends of the tray, generallycorresponding to cross joints in the brickwork. They should be bonded to the tray to givea waterproofseal. Stop ends prevent the possibility of water in thecavity running

down onto the tray and being thrown offits ends into the cavity · at the jamb of an openingsuch a concentrated flow of watercould run behind the verticaldpc in that part of the walling, wet the inner leaf and lead to dampness of the internal faceof the wall. Stop ends are particularly desirablewhen cavity insulation is installed. Steel lintels are available which are shaped and finished to act as a cavity tray without the addition of sheet dpc material.These lintels also require stop ends to be filled.

Weepholes are required in the outer leaf immediately above any cavity tray so that water collected on the tray can be diverted out to the exterior of the building. They should be formed in vertical cross joints at intervals not greater than 1m. There shouldbe not lessthan two weepholes over eachopening. It is usual to form weepholes by leaving a nominal 10 mm wide cross joint unmortared. The

height of the weephole is generallydetermined by the height of the brickbut it is not critical. It should be large enough to avoid any tendency to become blocked by debris. Weepholes formed between soldier bricks may be full height, but need only be about 40 mm. In tall buildings subjected to harsh exposure there has beenexperienceof rainpenetration due to high winds blowing into cavity wallsthrough weepholes and moving water up beyond the upstand of dpc trays. Proprietary devices are available to assist the formation of weepholes that allow water to drain from the cavity but restrict the ingressof wind andl or rain.

_

Tray ove, lintel note stop ends

_

Vertical dpc where cavity closed at jamb

Lapping of vertical dpcat jambs to openings in cavrty wall

Requirements for damp proof courses and cavity trays for specific parts of buildings At jambs of openings

Where a cavity wall is closed at the jambs of ope nings by masonry, a vertical dpc should be inserted to prevent moisture passing from the outer

leaf to the inner parts of the wall. The vertical dpc shou ld extend into the cavity at least 25 mm beyond the width of the closer and any cavity tray above shou ld exte nd beyo nd it tsee figure above). Insulation material may also be placed in this

Arrangement ofvertical dpcand insulalion at jambs to openings in a cavity wall

A frame in a n opening should be locat ed an d fixed in such a manner that transmission of water

past the vertical dp c is avoided . Where the frame is to be built in, the dpc should be secured to th e frame first. If the fram e is to be fixed later, the dp c should be left projecting within the opening. Vertical d pc's at openings shou ld be positioned to overlap any horizontal d pc at the sill of the opening and be overlapped by any cavity tray at the head [see figure above).

position to minimize cold bridging.

Proprietary closers are ava ilable which combine the functions of closing the cavityat the jamb, preventingmoisture transfer, stabilizing the masonry leaves, reducing

cold bridging and providing fixing for window or door frames. If these are used follow manufacturer's instructions for installation and linking with

assoc iated dpc's at the head and sill. A proprietary plastic cavity closer I frame fixing

Sills All pervious or jointed sills, or sub -sills, shou ld be provided with a dpc for the full length and width of the sill bed. The dpc should be overlapped by the vertical dpc's at the jambs of the openings [see figure on page 18). Where the sill is in contact with the inner leaf, the dpc should be turned up at the back and ends for the full depth of the sill(see figure on page 8).

Requirements for additional cavity trays with cavity insulation When cavity insulation is present but not installed throughout the fullvertical height of the cavity (eg. stopped at eaves level in gable ends) a cavity tray is required immediately above the insulation to protect from the hazard of mortar droppings or other debris forming a bridging of th e cavity on the top of the insulation . In buildings over 12 m high, with insulated cavity walls, cavity trays are required to subdivide the cavity so as to avoid surcharge by water that may penetrate the outer leaf of ma sonry. They should be insta lled at a maximum of 12 m above ground level and at a maximum spacing of 7 m thereafter. In framed building with brickwork cladding the trays required to subdivide the cavity can be the same as those associated with the cladding support system . In both these cases trays should step down a minimum of 150 mm towards the outer leaf and weepholes should be provided at intervals not greater than 1 m.

Addrtion al cavity tray 10 protect top of cavityinsulation

Additional cavity trays to subdivide tall walls with cavity insulation

Deta il of parapet showing dpc tray

External wall becomingan internal wall

Parapets

If, in its height, an external wallbecomes an internal wall at lower level, as inthe case of a roof abutting a wall (e.g. in a stepped terraceof houses, ora porch, garage orconservatory annex)a cavity tray shouldbe installed to drainthe cavity above the level of the lower roof.

Ina solid parapet wall a dpc shouldbe provided at a heightof not less than 150 mm above the top surface of an abutting roofsystem and lap overthe flashing to the roofing to give continuity,

Ahorizontal abutment requires a level cavity tray withstop ends and weepholes. When a pitched roofabuts such a wall, a cavitytray stepped to correspond with the slopewill be required; alternatively a system ofoverlapping preformed trays may be installed to collect and discharge water from the cavity. Ineithercase stop ends and weepholes are essential. Proprietary systems exist forthese applications.

In a cavity parapet wall a cavity tray shouldbe installed to provide the same function. It should step at least 150 mm within the cavity. When cavity fill insulation is installed the tray shouldstep down to the outer leaf(away from the roof]. When there is no cavityinsulation the designer should consider carefully which way to step the tray in any given case. It is saferto directwater towards the outer face (away from the roof]. Concern that this may cause staining on the face of the wall belowis exaggerated. Ifslopedinwards (towards the roof) experience shows that there is a danger in that rainwater may be driven below the tray and track along its underside and so gain accessto the inner leafof the wall, the underside of the roofcovering and the interior of the building. Itshouldbe noted that dpcs and cavitytrays impairthe structural integrity of the parapet and the wall beneath and also the coping above. Opc materialswith good bonding performanceshould be specified.

stability of the assembly the dpc can be placed in a beddi ng two or three courses below the to pmost one . All materials above the dpc must be frost

resistant. In cavity walls flexible dpc's require support overthe cavity to avoid sagging and deformation and to facilitate effective sealing of lapped joints.

Resistanceto waterpenetration should not prejudice provision for masonry movement. Movement control joints in the masonry should be carried th rough any coping or capping and sea lant applied as in the corresponding joint in the wall below. Consideratio n sho uld be given to copings and cap pings being displaced by lateral loads, and to the possibility of vandalis m. L-sha ped copings and Brickwork withflush capp ings canbe very successful. but requires extracare inthe selection of materials for durabili ~ tv. anundemanding oftheirweathering characteristics. and ofthe implicationsofdesignfeatures on weathering

Copings and coppings A coping is a construction that protects t he top of a wall and sheds rainwater clear of the vertical wall surfaces below, generally by having a weathered top surface and a throa ted overha ng to

clip-over copingsmay be more satisfactory insome situations. Where necessary, cop ings should be SUitably fixed down and may be doweled or jogglejointe d together. Copings a nd ca ppings to the sloping tops of gable end walls present particular problems of sta bility and security. They require careful consideration of the practicality of construction.

one or both edges. A capping is a construction at the top of a wall, but it does not shed rainwater clear of the wall surfaces below. Cappings are genera lly flush, but they may have featu res which, althoug h they overha ng the surface of the wall below, do not adequately protect it by throwing water clear.The traditiona l detail of bricks set onedge with tile creasing below sho uld be regarded as a cappi ng rather tha n a coping. Preferably parapet walls, chimney terminals, freesta nding walls and retaining walls shou ld be provided with copings. The drip edge of a throating should be POSitioned a minimum of 40mm from the face of the wall it is inte nded to protect. Where for

aesthetic or other reasons a cappingis used special care is needed in the choice of materials for durability, both for the capping itself and for the walling beneath. Where the capping or coping is [ointed, a continuou s sheet dpc should be provided in the

bedding mortarjoint.To increase the weight and

Copings givepositive protection against wetting ofwallingbelow

Chimneys Chim neys may be built in solid or cavity wall construction. Wherea chimney stack is incorporated in an outer cavity wall, preferably the outerleaf and cavityshould be continuous around the chimney stack for the full height of the outer wall and then comp letely surround the chimney stac k whe re is projects above the roof. Corbelling from the chimney breast may be necessary below the roof line, to sup port the outer leaf at the sides and back of the chimney stack. If the chimney is set in an internal partition or party wall and the roof is steeply pitched, a reasonable height of chimney willbe exposed in the roof void and a ny dampness in the masonry will be able to dryout in a ventilated roofspace. However, with a low pitched roof, whe n a chimney is located at the eaves, or the roofspace accommodates habitable rooms this beneficial effect will not apply and particular carein the design and construction of the roof/chim ney intersection wtll be necessary to prevent moisture penetrating into the masonry

below. Opc trays should be provided to prevent the

downward passageof water. Horizontal trays shou ld extend through the thickness of the chimney wall and into the flue liner,with an upturn at the inner face of the flue. Externa lly it should be linked with any flashing at the intersection of the chimney with the roof. The figure below illustrates typical arrangements.

It should be noted that a sheet d pc at the point of intersection with the roofreduces the structural integrity of the masonry, and the sta bility of the chimney stack and its resistance to lateral wind loading needs to be considered. Chimney stacks built in cavity work may be provided with a dpc tray of a material stiffenough to form a cavity tray without beingbuilt into the inner leaf and this

provides structural continuity. A horizonta l dpc shou ld always be provided below any coping or capping at the top of the stack unless it is a jointless, waterresistant material, egoa one-piece dense terracotta, slate orreconstructed stone unit, or a sheet metal assembly in one-piece or with waterproof joints.

Structuralframes Maso nry supported by a structural fram e, requires particular attention to be paid to the detai ling of trays and dpc's to ensure their continuity. Where cavity brickwork is supported on a n edge bea m, or floor slab, a cavity tray with a minimum upsta nd of 150 mm should be provided to prevent moisture penetration into the structure. The cavity trayshould be continuous around any column, or other structural member, that obstructs the cavity. When a structural memb er bridges the cavity, a vertical dpc should be included between the structural member and the external leaf, and stop ends fitted to any ad jacent cavity trays. Where complex shapes are needed, prefabricated cloaks should be cons idered to minimise difficulties of construction.

£eft

Opc trays andflashings in masonry chimney at roof penetration

Flashing s and weatherings

The material to be used should be sufficiently malleable to perm it dressing into shape, but sufficiently stiff to maintain its shapeand to resist

lifting by the wind . Meta l flashings ot her tha n lead should, preferably, be pre'formed . Flashings sho uld be bedded into the work a minimum of 25 mm, and be provided with welted ,

or otherwise sealed, joints, or adequate overlaps.

The designer shouldconsider how flashings areto be fixed and at what stage in the construction programme to provide secu re fixing and avoid damage to dpc's. The materials should be selected with due regard to the likelihood of corrosion and given protective treatment asnecessary.

To avoidstaining of masonryfrom the run-off of rain water, consideration should be given to the need for surface treatment of some metals.

CONCLUSION

Most external wallsareexpected to prevent rain penetrating to the interior of buildings .

In masonry cavity walls it is accepted that some water will pass thro ugh the outer leaf in prolonged periods of wind·driven rain, but the design of the wall is intended to dea l with this inevitable eventuality. The risk of furthe r penetration throug h the wa ll a nd into the building is minimized by the pro per des ign and installation of the wall's associated damp-proof systems. Environmental and ecanomic benefits have led to the incorporation of various types of thermal

insulationmaterials into modern cavity walls.

Effectiveinstallation met hods have been deve loped to ensure that this is done without impairing the wall's performance in bad weather.

The incidence of wind and rain experienced in the United Kingdom can be very testing, but walls with facing brickwork can efficiently meet the cha llenge. With care and attentio n to design and workmanship, stra ightforward and well established

construction methods can provide walls that are resistant to rain penetration and also attractive, durable and economical.

REFERENCES 1. Building Research Establishment. Repo rt Driving Rain Index (1976)

9. B5 6150 : 1991. British Stan dard Code of practice for painting of bu ildings .

2. BS8104: 1992. Britis h Standard Code of practice for Assessing exposure ofwalls to wind-driven rain.

10. B5 6477: 1992. British Standard Specification for

3. BRE Report BR 262 : 1994. Thermal insulation:

11. B58000 : Part 3: 1989. British Standard for workma nship on building sites : Code of practice

avoiding risks. 4. B5 5628: Part 3: 1985. British Standard Code of

practice for the use of masonry: Materials and components,design and workmanship. 5. BRE Digest 273 : 1983. Perforated clay bricks 6. B5 5262: 1991. British Standard Code of practice for external rendered finishes. 7 . British Cement Association publication

no.47.1 02. Appearance matters - 2: External renderi ng (1992) W Monks

8. BS 392 1: 1985. British Standard Specification for Clay bricks.

waterrepellents for masonrysurfaces.

for masonry. 12. Brick Development Association Building Note 1. . Brickwork· Good Site Practice. (1991) TLKnight 13. B5 8215: 1991. British Standard Code of practice

for design and installation of damp-proofcourses in masonryconstruction. 14. BS8102: 1990. British Standard Code of practice

for protection of structures against waterfrom the ground.

ISBN

o 900191 OS

8

ACKN OWLE DGEM EN TS All photography by Brick Development Association except as follows: Frankwalter - covers,p.u upper. p.21 lower Cover & p.1IglI :z 1: Houses at Victoria Park. Virginia Water, Surrey

....rchitects: The Howell Smith Partnership Page 4:

Cascades Hotel and flats, Isle of Dogs, London E14 Architects: ClWG

Page 11 upp er :

Flats & maisonettes, Hadrian Estate, Hackney. London E2 Architects: Levitt Bernstein Associates li d

Page 11 lower:

Compass Pomt HouSing. Isleof Dogs. LDndon E14 Archuects:

Page 21 upper:

~~mVD~on

HartlepooJeve Centre, develand Architects: TheCulpm Partnership

All enquiries should be addressed to the a utho r at the Brick Development Assoc iation. The contents of this pubhcatmnare intended for general guidance only and any person intendmg to use these contents for the purpose of design. construction or

repair of bnckworkor any related prcject should first consult a Professional Adviser. TheBrick Development Association. Itsservants. and any persons who contributed to or who were In any way connected With this publicationaccept no babihty arising from negligence or otherwise howsoevercaused for any inluryor damage to any person or property as a result of any use or reliance on any method, product. instruction. idea,or other contents of this publication.