BS 8102 2009 - ScandiProof.com

BS 8102:2009

Code of practice for protectionof below ground structuresagainst water from the ground

BRITISH STANDARD BS 8102:2009

ContentsForeword iii1 Scope 12 Normative references 13 Terms and def ini t ions 24 Design phi losophy 35 Site evaluat ion 75 Water-resisting design 97 General construct ion issues 198 Type A (barrier) protection 209 Type B (structurally integral) protection 2610 Type C (drained) protect ion 3111 Remedial measures 34

Bib l iography 37

List of figuresFigure 1 - Design f lowchart 5Figure 2 - Schematic il lustrations of Type A, Type B and Type Cwaterproofing protection 72Figure 3 - Sub-surface drainage posit ionin g 18Figure 4 - Effect of structure on appl ied waterproof ing barr ier 21Figure 5 - Pi le to f loor slab junct ion 22Figure 5 - Effect of bonded or part ial ly bonded barr iers 23

List of tablesTable 1 - Use of different protection types based on watertable classi f icat ion 15Table 2 - Grades of waterproof ing protection 15Table 3 - Categories of barr ier mater ials 23

Summary of pagesThis document comprises a front cover, an inside front cover;.

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ForewordPubl ishing i nformation

This Bri t ish Standard is publ ished by BSI and came into effect on30 November 2009. lt was prepared by Technical Committee 81526,Geotechnics. A list of organizations represented on this committeecan be obtained on request to its secretary.

Supersession

This Bri t ish Standard supersedes BS 8102:1990, which is withdrawn.

Information about this document

This Bri t ish Standard was or iginal ly publ ished in 1990, supersedingthe earl ier CP102 (1973). This is a f ul l revision of the standard, andintroduces the fol lowing pr incipal changes:

a) a number of recent developments are addressed, which areimportant when specify ing, designing and construct ing belowground structures, including:

1) more deep construct ion in congested urban areas;

2) an increase in the provision of resident ial basements;

3) development and use of new mater ials for waterproof ing;

b) a more detailed assessment is provided of the risks inherent inbelow ground construction and how these might best be addressed.

In addit ion to the introduct ion of these key changes, the publ icat ion ofthe Eurocodes and the approaching withdrawal of the correspondingBri t ish Standards make this revision t imely.

It is noted that the figures used in this document are only representativeof different installation methods, and should not be translated directlyinto practice without first checking all the parameters specific to theinstal lat ion.

Use of this document

As a code of pract ice, this Bri t ish Standard takes the form of guidanceand recommendations. l t should not be quoted as i f i t were aspecif icat ion and part icular care should be taken to ensure that c laimsof compl iance are not misleading.

Any user claiming compl iance with this standard is expected to be ableto justify any course of action that deviates from its recommendations.

I t has been assumed in the draft ing of this document that theexecut ion of i ts provisions is entrusted to sui tably qual i f ied andexperienced people, for whose guidance i t has been prepared.

Presentational conventions

The provisions in this standard are presented in roman ( i .e. upr ight)type. l ts recommendations are expressed in sentences in which thepr inc ipa l aux i l ia ry verb is "shou ld" .

Commentary explanation and general informative material is presentedin smaller italic type, and does not constitute a normative element.

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BS 8102:2009 BRITISH STANDARD

Contractual and legal considerations

This publ icat ion does not purport to include al l the necessary provisionsof a contract. Users are responsible for its correct application.

Compliance with a British Standard cannot confer immunity fromlegal obligations.

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1 ScopeThis Bri t ish Standard gives recommendations and provides guidanceon methods of dealing with and preventing the entry of water fromsurrounding ground into a structure below ground level.

It covers the use of:

a) waterproof ing barr ier mater ials appl ied to the structure,

b) structural ly integral watert ight construct ion; and

c) drained cavity construct ion.

It also covers the evaluation of groundwater conditions, risk assessmentand opt ions for drainage outside the structure.

I t appl ies to structures which extend below ground level and those onsloping si tes.

This Bri t ish Standard does not give recommendations concerning theuse of embedded heat ing in structures, f loors and wal ls or for thespecial requirements in connect ion with the design and construct ionof cold stores.

NOTE Structures are generally characterized as "deep" if they have morethan one storey below ground level, or "shallow" if they have only asingle storey below ground. This standard is applicable to both.

2 Normative referencesThe fol lowing referenced documents are indispensable for theappl icat ion of this document. For dated references only the edit ioncited applies. For undated references the latest edition of thereferenced document ( including any amendments) appl ies.

BS 743:1970, Specification for materials for damp-proof courses

BS 5930, Code of practice for site investigations

BS 5100-3, Building and civil engineering - Vocabulary - Part 3: Civilengineering - General

BS 8004, Code of practice for foundations

BS 8204-1, Screeds, bases and in situ f loorings - Part 1 : Concrete basesand cement sand levelling screeds to receive floorings - Code of practice

BS 8747, Reinforced bitumen membranes (RBMs) for roofing - Guideto selection and specification

BS EN 1504, Produc$ and systems for the protection and repair ofconcrete structures - Definitions, requirements, quality control andeva I u ati o n of confo rm ity

BS EN 'l 992, Eurocode 2: Design of concrete structures

BS EN 1993, Eurocode 3: Design of steel structures

BS EN 1993-5, Eurocode 3: Design of steel structures - Part 5: Piling

BS EN 1997, Eurocode 7: Geotechnical design

BS EN 10210, Hotfinished structural hollow sections of non-alloy andfine grain steels

BS EN 10219 , Cold formed welded structural hollow sections of non-alloy and fine grain steels

BS EN 10248, Hot rolled sheet piling of non alloy steels

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BS 8'102:2009 BRITISH STANDARD

BS EN 10249, Cold formed sheet piling of non alloy steels

BS EN 12063 , Execution of special geotechnical work - Sheet pile walls

BS EN 12970 , Mastic asphalt for waterproofing - Definitions,requirements and test methods

3 Terms and definitionsFor the purposes of this Bri t ish Standard, the terms and def ini t ionsgiven in BS 6100-3 and the fol lowing apply.

3.1 cavity drain membranedimpled, f lexible, high-density polymer sheet, which can be placedagainst the internal face of a structure after construction and isdesigned to intercept water penetrating the structure and direct it toa drainage system

3.2 cut-off wallembedded retaining wal l (see 3.4) designed to surround and seal-offan area, to inhibi t water inf low from the surrounding area

3.3 damp areaarea which, when touched, might leave a l ight f i lm of moisture on thehand but no droplets of water ( i .e. beading)

NOTE This definition has been taken from the ICE publication,Specification for piling and embedded retaining walls [1].

3.4 embedded retaining wallwall used to support the sides of an excavation, installed in advance andpenetrating below the lowest level of the below ground construction

NOTE Within this standard the principal forms considered constitute theprimary permanent wall for the below ground construction, and are takenas diaphragm walls, contiguous or secant piles (which may be installed indifferent configurations) or steel sheet piles.

3.5 ground barr ierimpermeable barr ier between the structure and the ground intendedto prevent or impede the ingress of water; dampness, radon, methaneand other ground gases and contaminants

3.5 loading coatlayer of mater ial designed to hold a Type A waterproof ing mater ial inplace when resist ing water pressure

3.7 perched water tablereservoir of water in the ground maintained permanently or temporarilyabove the standing water level in the ground below it, and is caused bythe presence of an impervious soil or a stratum of low permeability

3.8 seepageslow transmission of water through discrete pathways of a structure

NOTE This can also be known as weeping, as defined in ICE publication,Specification for piling and embedded retaining walls [1].

3.9 tankingappl icat ion of an appropriate waterproof ing barr ier to the wal ls, thebase slab and, where relevant, the roof of a below ground structure,such that the ent ire envelope of the structure below ground isprotected against water ingress

NOTE A cavity drain membrane is not considered to constitute tanking.

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3.10 Type A (barrier) protectionprotection against water ingress which is dependent on a separatebarrier system applied to the structure

3.11 Type B (structurally integral) protectionprotection against water ingress which is provided by the structure

3.12 Type C (drained) protectionprotection against water ingress into usable spaces which is providedby the incorporation of an appropriate internal water managementsystem

3.13 vapour checkmembrane or other element that restr icts the transmission of watervapour

3.14 waterproofimpervious to waterNOTE This can also be known as "watertight".

3.15 waterproofinga ppl ication of waterproof/water-resisti n g materi a I s

3.15 waterproofingbarriermaterial that does not permit the transmission of free water, butmight al low some water vapour permeabil i ty

3.17 waterproofingsystemmaterials and methods used to protect a structure from water ingressand might also provide resistance to the diffusion of water vapour

3.18 water resistanceabil i ty of a material to resist water penetration

3.19 waterstopmaterial designed to inhibit the transmission of water through jointsin the structure

3.20 water vapourwater in its gaseous state

3.2'l water vapour resistanceabil i ty of a material to resist water vapour penetration

4 Design phi losophy

4.1 GeneralI t is essent ial for the success of any project involving below groundstructures that strategies for dealing with groundwateL soil gasesand contaminants are considered from the very earl iest stages of theplanning and design processes.

For new structures, it is recommended that the structural design,overal l weatherproof ing design, waterproof ing design andconstruction processes are considered together, as they generallyinteract.

In addit ion, i t is recommended that, dur ing the design process andat all stages of the construction process, the designers, specialists,manufacturers/suppliers and i nstal I i ng contractors establ ish and

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maintain effect ive channels of communicat ion. Regular and clearcommunicat ion coupled with good si te supervision al lows variat ionsand amendments to the design to be planned and executed withoutcompromising the performance of the waterproofed structure (seealso 4.2).

4.2 Design teamThe advice of a geotechnical special ist should be sought on thegeology and hydrogeology, the external drainage opt ions andgroundwater condit ions (see Clause 5).

A waterproof ing special ist should be included as part of the designteam so that an integrated waterproof ing solut ion is created. Thewaterproof i ng special ist shou ld:

a) be sui tably experienced;

b) be capable of devising solut ions that accommodate the var iousproject constraints and needs;

c) provide the design team with information and guidance thatassists with and inf luences the design, instal lat ion and futuremaintenance of the waterproofed structure.

NOTE The waterproofing specialist could be the manufacturer ormaterial supplie4 provided that the manufacturerlsupplier has therelevant expertise.

Al l design decisions made by others that might have an impact onthe waterproof ing design should be brought to the attent ion of thewaterproof i ng special isVdesigner and i nsta | | ing contractors. Finaldecisions and any recommendations should be approved by thedesigner.

4.3 Principal considerations

4.3.'l GeneralIn order to develop a robust design for protecting a structure againstgroundwatel the fol lowing factors should be assessed:

a) the l ikely highest level of the water table, the drainagecharacteristics of the soil and other site-specific properties(see Clause 5);

b) the appropriate waterproof ing measures (see Clause 5), i .e.Type A, B or C protection and, where necessary, external drainagebased on:

1) the results of the si te evaluat ion, including the classi f icat ionof the water table; and

2) the intended use of structure, with considerat ion givento any requirement for future f lexibi l i ty. This should beundertaken in consultat ion with the cl ient;

c) the appropriate type of primary waterproofing system (seeClause 8, Clause 9 and Clause 10).

NOTE 1 The general principle 6 to assess the risk of water reaching thestructure and then to se/ecf a waterproofing system capable of achievingthe req u i red i nterna I e nvi ron ment.

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NOTE 2 Mechanical heating and ventilation often play an important rolein creating the internal environment, particularly where higher gradesare required. The design of such sysferns is a specialist activity, outside thescope of this standard.

Condensation may also be controlled by the provision of adequateventilation (assrsted by heating), coupled with the suitable treatment offloor and wall surfaces.

A three-dimensional rev iew of s t ructure and waterproof ing should beundertaken so as to ident i fy any complex geometr ies, which are notreadi ly ident i f ied f rom normal two-dimensional deta i ls .

Serv ice entr ies are par t icu lar ly vu lnerable to water penetrat ion;where they cannot be avoided, they should be carefu l ly deta i led,incorporat ing seal ing, to min imize the r isk of water ingress (see 8.1.3) .

NOTE 3 The three-dimensional review needs to include detailedinformation on the proposed waterproofing system (e.9. the effectthat this has on wall base details, laps in membranes and waterstops).Examples of complex geometries are corner details and where the walladjoins: the base slablfoundation; the superstructure; differing floorlevels; and windows below ground.

4.3.2 Defects and remedial measuresAn idealwaterproofing solution would be defect-free. However,it should be noted that two types of defects might occur in anywaterproofing, where a structure is subjected to water pressure,and this could mean that the required internal environment is notachieved. These defects are as follows:

a) defects owing to poor workmanship or the inappropriate use ofmater ials;

b) defects owing to the specific properties of the materials being used.

NOTE Reference to "defects" does not apply to normal designed flexuralcracks or surface crazing in concrete elements but only to through cracking,which might need to be locally sealed.

I t is essent ial that the construct ion methods and mater ials used toreal ise the design are such that the defects in a) are avoided.

The defects in b), which are general ly minor, should be recognizedand catered for in the design. Cont ingency planning for deal ing withany local ized defects or system fai lure that ar ise should be includedas part of the overall water-resisting design for the structure (see alsoClause 11) .

In ei ther case, the issue of repairabi l i ty should be taken into accountand the feasibi l i tv of remedial measures assessed.

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Figure 'l Design flowchart

COMMENTARY ON FIGURE 1Figure 1 outlines the principalfactors and stages that need to beaddressed in order to produce arobust waterproofing solution fora below ground structure.

It demonstrates that some mattersare interrelated and that adegree of iteration might resultfrom a need fo address buildabilityand repairability. The principalissues (boxes) do not necessarilyneed to be addressed in theorder shown but all need to beu nde rstood a n d eva I uated.

INITIAL INFORMATIONDesign philosophy (see Clause 4)r Design team (4.2)Site evaluation (see Clause 5). Desk study (5.1.1)r Risk assessment (5.1.2)r Water table classification (5.1.3)Review of structure. Type (e.9. new or existing?)o Intended user Foundation form and designe Construction methodology

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STRUCTURAL DESIGN CONSIDERATIONS

SELECTION OF TYPE A, B or CWATERPROOFI NG PROTECTION

IS COMBINED PROTECTION NECESSARY?(See 6.2)

SELECTION OF PRIMARYWATERPROOFING SYSTEM

(See Clause 8, Clause 9 and Clause 10)

HAS BUILDABILIry BEEN CONSIDERED?

HAS REPAIRABILIry BEEN ADDRESSED?

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5 Site evaluationCOMMENTARY ON CLAUSE 5

Attention is drawn to the fact that many of the rssues addressed inthis clause are also relevant to the design of the structure itself. Forfurther guidance, see the relevant Eurocodes, e.g. 85 EN 1992 orBS EN 1997.

5.1 General

5.1.1 Desk studyA desk study should be carr ied out in accordance with BS 5930 andBS EN 1997:

a) to assess the geology and hydrogeology, including soi lpermeabi l i t ies, f lood r isk, radon, methane and other groundgases and contaminants (e.9. chlor ides and acids);

b) to assess the topography of the surrounding ground in relat ion tothe below ground structure;

c) to establ ish the l ikely highest level of the water table and thepotential for the occurrence of a perched water table; and

d) to ident i fy any missing ground and groundwater information,which should then be obtained by undertaking a si teinvest igat ion in accordance with BS 5930 and BS EN 1997.

NOTE Guidance on best practice in ground investigation, laboratory andfield-testing for embedded retaining walls is given in CIRIA publicationcs80 [2].

The drainage character ist ics from analysis of the soi l should bedetermined in accordance with BS 8004.

5.1.2 Risk assessmentNOTE 1 The principal risks with respect to water ingress into structuresare the external environmental conditions.

A r isk assessment should be carr ied out which considers the long-termwater pressures, the effects of surface water infiltration and the useof external drainage and cut-off wal ls.

Risk assessment should also consider:

a) the effects of climate change, burst water mains and sewers,adjacent trees, sulfates, radon, methane and other ground gasesand contaminants; and

b) where external drainage is proposed, the effects of drawdownon adjacent structures, the potent ial s i l t ing of drainage andbiofoul ing issues.

Even when the si te invest igat ion indicates dry condit ions, the r isk ofsome water logging (see Note 2) in the future should be assumed.

NOTE 2 Even in a permeable subsoil, groundwater requires time to drainaway and this can result in limited pressure periodically coming to bearagainst the structure.

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5.1.3 Water table classificationWhere assessment of the water table is undertaken, this should beclassed into the fol lowing three categories, which can then be usedto determine the sui tabi l i ty of di f ferent types of waterproof ingprotection (see 6.2).

. High - where the water table or perched water table is assessedto be permanently above the underside of the base slab.

r Low - where the water table or perched water table is assessed tobe permanently below the underside of the base slab. This onlyappl ies to free-draining strata.

. Variable - where the water table fluctuates.

NOTE ln certain ground conditions, external drainage systems can beused to convert the "high" and "variable" water tables to the "low"condition (see also 6.3).

s.2 Inspection and survey for existing structures

5.2.1 GeneralFol lowing an assessment of the external r isk (see 5.1.2), acomprehensive survey should be undertaken of any exist ingwaterproof i ng arrangements.

The structure should also be examined in order to determine anypotent ial movement that might occur between the wal ls and f loor.

NOTE 1 The base slab of many older structures is likely to abut theexternal walls. This can give rise to movement between wall and floor.Special flexible joint details might be required so that strains in thewaterproofing materials are controlled within acceptable limits wherebonded or surtace-applied barrier materials are used in such situations.Similar details might also be required at other locations where structuralmovement can occur.

NOTE 2 Less movement would be expected rn cases where the floor is setinto the wall although horizontal movement can occur unless the floor isreinforced such as to achieve the necessary fixity.

As the space available in below ground structures is often convertedinto habitable rooms during refurbishments, the survey shouldalso consider the previous use, e.g. this might have been such thatdampness was of less concern than for the proposed use.

NOTE 3 Existing waterproofing might have to be removed completelyand replaced with an entirely new system, although in some instancesit might be possible to apply a Type A barrier or a Type C drained cavitysystem directly. These systems can be considered where there is no existingwaterproofing but the suitability of Type A barrier materials depends onthe characteristics of the surface of the wall or floor.

5.2.2 External wallsAn old external cavity form of waterproofing protection might beencountered that is not immediately obvious. Where an externalcavi ty is found, i t should be inspected to conf irm that:

a) the cavi ty is not br idged by debris;

b) any drainage is st i l l funct ioning and has not been si l ted up; and

c) air br icks are not obstructed by soi l or vegetat ion.

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NOTE 1 An example of an external cavity is where an inner wall,load-bearing or otherwise, has been built with a cavity between it and anearlier retaining wall. This cavity might be closedlcapped with a plinth,and would typically be drained at the base and ventilated by air bricks.

I t should be establ ished whether wal ls are ear th reta in ing or f reestanding as there might be instances where the waterproof ingmeasures have not been cont inued a long internal wal ls abut t ing theexternal reta in ing wal l .

NOTE 2 Where the external wall is of solid construction, there might beno waterproofing or there might have been previous attempts to maskdampness. Many such applications can be incomplete or ineffective. ltis possible that the attempted waterproofing was inappropriate for theprevailing external conditions or the wall surtace to which it had beenapplied.

The survey should inc lude any construct ions which abut the mainstructure, such as garden wal ls and arches under s teps, as these are apotential source of moisture transfer.

5.2.3 FloorWhere drainage t i les have been used to cover the f loor; they shouldbe assessed to confirm that they have sufficient strength to withstandloadings from wal ls, plant, equipment, vehicles, etc. , appropriate tothe intended use.

Where no-fines concrete has been used as a drainage layer, thisshould be simi lar ly assessed to conf irm that i t has suff ic ient strengthto withstand loadings and is st i l l draining effect ively.

NOTE 1 Drainage tiles are typically made from clay or concrete. Both tilesand no-fines concrete have widely been replaced by cavity drain membranes.

The f loor should be thoroughly surveyed for s igns of moisturepenetrat ion.

NOTE 2 Moisture from the ground can move across abutting constructionsat any level and in some conditions running water might be encountered.

Considerat ion should also be given to:

a) the ability of any surface to accept the proposed waterproofing;

b) the effect that any proposed waterproofing system is likelyto have on stresses imposed on the existing structure bygroundwater once the waterproof ing system has been instal led.

6 Water-resisting design

6.1 GroundwaterWaterproof ing measures should be designed on the basis of waterto the ful l height of the retained ground at some t ime during thestructure's life where:

a) no detai led geological or hydrogeological assessment has beenundertaken;

b) the results of the soi l invest igat ions are inconclusive with respectto groundwater;

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c) the ground drainage character ist ics are unrel iable;

d) the drainage measures (ei ther internal or external) are unrel iableor un-maintainable and inf i l t rat ion cannot be control led.

Protection against water ingress from the following three sourcesshould be considered:

1) the inf low of surface wateL ranging from percolat ion of rain toinundat ion of water from burst water mains (see 5.3);

2) the water pressures acting on the external retaining wall system;

3) the water pressures below the base slab.

The water-resist ing design should enable the system to withstand apre-determined head of water or control the water before it reachesthe structure.

One or both of the fol lowing methods may be used, in conjunct ionwith the waterproofing protection (see 6.2), to reduce waterpenetrat ion, depending on the condit ions of the si te and the requiredinternal environment:

i) exclusion of surface water (see 5.3);

i i ) sub-surface drainage (see 5.4).

6.2 Waterproofing protection

6.2.' l GeneralOne, or a combinat ion, of the fol lowing types of waterproof ingprotect ion should be selected:

a) Type A (barrier) protection;

b) Type B (structurally integral) protection;

c) Type C (drained) protection.

When making this select ion, considerat ion should be given to:

1) the need for combined protection (see 5.2.2);

2) the water table classi f icat ion and required performance level(see 6.2.3);

3) the need for continuity in the protection (see 6.2.4).

NOTE Examples of the three types of waterproofing protection are givenin Figure 2.

There is a range of waterproofing systems that can be incorporated ineach type of waterproofing protection and these should be assessedin accordance with Clause 8, Clause 9 and Clause 10, as appropriate,and relevant manufacturers' data sheets to confirm that the systemselected is sui table for the structure to which i t is to be appl ied.

I t is noted that the manufacturer 's recommendations for instal lat ion,including provision of protect ion, should always be fol lowed.Simi lar ly, recommendations for f ix ings where proprietary products areused should be fol lowed.

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In cases where the below ground structure is ful ly bur ied or thesubstructure extends beyond the superstructure, protection should beprovided against water ingress through the roof s lab, for example by:

i) encouraging water to drain away from the structure;

i i ) providing drainage above the roof s lab;

i i i ) using an external barr ier.

For existing structures, the following types of waterproofing systemsshould be considered, subject to their sui tabi l i ty for appl icat ion andtheir abi l i ty to be repaired:

. an internal Type A waterproofing barrier on a structure ofsuitable strength and stiffness, built of concrete or masonry(subject to the condition of the surface) [see Figure 2a)];

. a drained cavity to the wal ls and f loor, using a Type C cavity drainsystem [see Figure 2c)].

In situations where the use of a waterproofing system covered bythis standard is either not achievable or not cost effective, othermethods may be used i f they can be shown to lead to simi lar results.However, the r isks and impl icat ions of such methods should beinvestigated and recorded.

6.2.2 Combined protection

Considerat ion should be given to the use of combined protect ion(i.e. Type A and Type B, Type A and Type C or Type B and Type C)where in a single system:

a) the assessed risks are deemed to be high (see Clause 5);

b) the consequences of fai lure to achieve the required internalenvironment are too high; or

c) additional vapour checks are necessary for a system whereunacceptable water vapour transmission can occur.

Although structures with Type B protection are designed to be waterresistant, addit ional waterproof ing systems may be appl ied internal lyor externally to control water vapour movement, where appropriate.

An in-si tu " l iner" wal l designed to provide Type B protect ion canbe cast inside an embedded retaining wal l to provide combinedprotect ion. In some cases, a ful ly bonded barr ier might also beprovided between the two elements.

Although structures with Type C protection are designed to controland manage seepage into a structure, where this is unacceptably highthe water resistance of the structure should be improved prior tothe instal lat ion of the Type C protect ion, by the appl icat ion of ei therType A or Type B protection.

When combining types of protect ion, the compatibi l i ty of thedifferent protection types should be assessed in order to minimize ther isks and negate the need for remedial measures.

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Figure 2 Schematic il lustrations of Type A, Type B and Type C waterproofing protection

a) Type A (barrier) protection

Key

1 Externalwaterproofing

2 Masonry or concrete wall, as appropriate (see Table 1)

3 Concrete floor slab

4 Sandwichedwaterproofing

5 Loading coat

5 Internalwaterproofing

b) Type B (structurally integral) protection

Key

1 Water-resistant reinforced concrete wall and slab

2 External or internal (within wall) waterstop, as required

3 Waterstop required at junction between wall and slab and at all construction joints

4 Concrete/steel oiled wall

5 Water-resistant reinforced concrete floor slab or slab with added barrier6 Waterstop at junction to follow profi le of wall

7 Piled wall might need to be faced to achieve desired water resistance (see Table 1)

NOTE Seek the manufacturer's advice with respect to waterstops to suit the specific construction.

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Figure 2 Schematic illustrations of Type A, Type B and Type C waterproofing protection (continued)

c) Type C (drained) protection

Key

1 Cavity drain membrane

2 lnner skin (render, dry l ining or wall ing, depending on system)

3 Maintainable drainage channel with pipe connection to suitable discharge point

4 Sump formed in situ or pre-formed

5 Pump

6 Wall cavity

7 Reinforced concrete/steel pile or diaphragm wall

8 Drainage channel

9 Waterstop at junction to follow wall profi le

10 Internal block wall'11 Access point(s) to drainage

12 Floor slab with integral protection and/or added membrane (internal or external)

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6.2.3 Water table classification and grades of waterproofingprotection

When selecting a type of waterproofing protection, Table 1 and Table 2should be taken into account, in conjunction with the following points.

a) During the l i fe of the structure, some degree of groundwaterpressure is l ikely to bui ld up against the chosen waterproof ingsystem.

b) Cracking or defective construction joints can provide a potentialpath for water ingress.

c) Water ingress can occur where there is groundwater pressure. lf thisis not consistent with the required performance level (see Table 2):

1) considerat ion should be given to the form and feasibi l i ty ofremed ia lwork ;

2) i f remedial work is not possible, the design should be al tered.

d) There are a number of risks associated with not carrying out plannedmaintenance for structures with Type C protection, e.g. pump failure(see 10.3).

The designer should discuss these points with the cl ient pr ior todeciding on which typeG) of waterproofing protection to use. Thefol lowing should also be taken into account:

1) in i t ia l capital costs compared with costs for future maintenanceand any necessary upgrades;

2) the scope for test ing during instal lat ion;

3) the r isks associated with aggressive groundwater and otherground contaminants, which might require the use of a specif icprotection barrier;

4) the need or abi l i ty to provide heat ing and/or vent i lat ion and theconsequences ar is ing in terms of water vapour.

NOTE This might call for the adoption of an improved gradeof waterproofing protection (see Table 1 and 6.2.2) or activeenvironmental control in order to manage water vapour (see Table 2).

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BS 8102:2009

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BS 8102:2009

Table 2 Grades of waterproofing protection

BRITISH STANDARD

Grade Example of use of structureA) Performance level

Car parking; plant rooms (excludingelectrical equipment); workshops

Some seepage and damp areas tolerable, dependent onthe intended useB)Local drainage might be necessary to deal with seepage

Plant rooms and workshopsrequir ing a dr ier environment ( thanGrade 1); storage areas

No water penetration acceptableDamp areas tolerable; vent i lat ion might be required

Venti lated resident ial and No water penetrat ion acceptablecommercial areas, including off ices, Vent i lat ion, dehumidif icat ion or air condit ioningrestaurants etc.; leisure centres necessary, appropriate to the intended use

The previous edition of this standard referred to Grade 4 environments. Howeve4 this grade has not beenretained as its only difference from Grade 3 is the performance level related to ventilation, dehumidification orair conditioning (see BS 5454 for recommendations for the storage and exhibit ion of archival documents). Thestructura l form for Grade 4 could be the same or s imi lar to Grade 3.

B) Seepage and damp areas for some forms of construction can be quantif ied by reference to industry standards,such as the ICE's Specification for piling and embedded retaining walls [1].

6.2.4 Continuity of waterproofing protectionThe need for cont inui ty in the waterproof ing protect ion should also beconsidered when selecting a type of protection. In most circumstances,the protect ion should be cont inuous. In certain si tuat ions, e.g. where adrained cavity is combined with an underslab membrane, discont inui tywith respect to waterproofing can be acceptable subject to carefuldetai l ing and an appropriate assessment of r isk (see 5. '1.2 and Note 2).Any bui ld up of water should be permanently control led by a watermanagement system.

The proposed type of foundat ion and i ts sui tabi l i ty for providingcontinuity of waterproofing (where so required) should be assessed.

NOTE 1 Continuity can be provided in situations where the surface orstructure of the wall and foundation provides uninterrupted positioningof the waterproofing measures.

In existing structures, assessment of any direct or potential discontinuityshould be undertaken in order to determine the need for specialwaterproofing details, e.g. to overcome the effects of future movement.

NOTE 2 Discontinuity of waterproofing protection might not beacceptable if there is a need to manage radon, methane and other groundgases and contaminants (see 6.5).

6.3 Exclusion of surface waterWhere pract icable, prov is ion should be made to prevent or reducepercolat ion of ra inwater in to the ground.

NOTE 1 BS EN 752 gives guidance on collecting and disposing of surfaceand sub-surtace water.

NOTE 2 Burst water mains and leaky sewers can provide additionalsources of surface water. These can affect perched water tables. Thedrainage behind the wallneeds to be able to cope with the highestinflow rates, e.g. the burst water main, which might not be practicable incoarse-grained soils.

1 6 o @ B 5 1 2 0 0 9


G.4 Sub-surfacedrainageWhere sub-surface drainage is deemed necessary to lower thepotential for hydrostatic pressure on the waterproofing system andlessen the risk of water ingress through defects, it should be providedby one of the fol lowing methods:

a) permeable granular f i l l ;

b) no-f ines or hol low blockwork;

c) geosynthetic drainage composite;

d) underslab drainage.

NOTE 1 Figure 3 gives examples of the positioning of land drains,drainage channels and sub-surface drainage.

Such provisions should be made maintainable where they are used tocontrol the level of water in a structure that does not in itself provideadequate water resistance.

Where practicable, water should be kept from prolonged contact withperimeter structure wal ls or base slabs by porous or open jointed landdrains, combined with a geosynthet ic drainage composite instal ledto the ful l height of the earth-retaining wal l and laid to proper fal lsaround the perimeter of the structure, adjacent to the wall footingand, where appropriate, beneath the slab i tsel f .

The sub-surface system should be graded to an open outlet below thelevel of the lowest slab, such as to a stormwater drain protected by apumped surcharge device or to a pumped sump, and can also providea suitable outfal l for any sub-f loor drainage.

Perimeter drainage at f loor level is l ikely to lower the groundwatertable to a degree that var ies with the permeabi l i ty of the subsoi l andthe possible consequences of this (such as permanent lowering of thewater table in the surrounding area) should be taken into account.Any existing system of land drains should be tested, checked and onlyretained i f both appropriate and maintainable. Any local diversionsnecessary should retain the exist ing geometry so far as pract icablewith new and easi ly maintainable pipework.

Care should be taken so that no damage is caused in nearby structures.Where deep structures are contemplated in built-up areas, groundwaterlowering should not be undertaken without careful investigation inconjunction with a groundwater specialist (see 4.2). Perimeter wallsproviding a cut-off into an impervious layer or stabilization of granularsubsoils by grout injection or similar alternative treatments may beconsidered instead.

NOTE 2 For structures in coarse-grained soil, with variable and highwater tables (see 5.1.3), the f low rates are likely to make it impracticableto pump for the design life of the structure. ln these caset a hydrauliccut-off wall into fine-grained soils is required to isolate the ground belowthe base slab. This enables an underslab drainage system to relieve thewater pressure below the base slab.

NOTE 3 For structures in fine-grained soil, with variable and high watertables (see 5.1.3), the flow rates are more likely to make it practical topump for the design life of the structure. A drainage system may beprovided outside the retaining wall to control the water pressures. Anunderslab drainage system may also be provided below the base slab tocontrol the water pressures.

@ BSI 2009 . 17


Cut-off wal ls are formed from diaphragm wal ls, secant pi les or steelpi les. Over the excavated wal l depth remedial works can be carr iedout on leaky wal ls. This is not feasible for the length of wal l belowformation. Therefore, specif ied tolerances should be such that there isadequate intersect ion between pi les or provision of cont inuous waterbars at diaphragm wal l panel jo ints and part icular at tent ion should begiven to workmanship.

In interbedded soi ls, rel ief wel ls may be used below formation level.The cut-off wall may also be used to reduce the flow rate and controlthe drawdown outside the si te.

Figure 3 Sub-surface drainage positioning

\vt-€rt,.l

,/

a) Construction without a toe

Key'l Maintainable land

drain (see 6.4) not tobe positioned closerthan a l ine of 45 'from the underside ofthe s lab/b l ind ing orwith an invert abovethe upper surface ofthe floor slab

2 Measures to controlwater vapour mightbe necessary wherethe invert of theland drain is abovethe underside of thefloor slab

3 Incorrect positionof land dra in. whichcan cause hydrostaticpressure on barrierleading to wateringress if defects areoresent

4 Subsoi l dra inagelayer, whereappropriate (see 6.4)

5 Structural wall andfoundation slab

-\<i,\\!r/

\- //- i\a*\- \)'-/ ./,/

b) Construction with a toe

1 8 . @ 8 S 1 2 0 0 9


5.5 Ground gasesThe inser t ion of a ground barr ier for the prevent ion of radon,methane and other ground gases and contaminants f rom enter ing astructure should be considered in the design, choice of the mater ia lsand insta l la t ion of any waterproof ing system.

NOTE 1 Attention is drawn to the Building Regulations [3]. Furtherguidance on the characterization and remediation of ground gases rsgiven in BS 8485.

NOTE 2 The maps of areas where basic or full protection againstradon needs to be provided are contained in the Building ResearchEstablishment (BRE) repofts BR2l1 [4], 8R376 [5], 8R413 [6] and the HealthProtection Agency (HPA) documenf Radon in Dwellings in Scotland: 2008Review and AIlas [7].1)

7 General construction issues

7.1 Site de-wateringWhere appropriate, the si te should be de-watered at least unt i l sucht ime as the below ground structure and waterproof ing is completed(see 6.4 regarding the effects of dewatering on nearby structures).

On open sites, where any adjacent structures are sufficiently remote tobe unaffected by groundwater lowering, de-watering or pumping fromcareful ly arranged sumps with appropriate drainage channels should becont inuous whi le the laying of any waterproof ing barr ier mater ials isin progress and until all loading coats have hardened and the structurehas developed sufficient strength to resist the full water pressure.

7.2 Structural elementsForms of construction to receive below ground waterproofingprotect ion may include the fol lowing.

a) Walls - constructed from:

1) masonry (plain or reinforced br ick or block);

2) precast concrete;

3) in-si tu concrete, ei ther cast in form (plain, reinforced orprestressed) or embedded walls; or

4) steel or concrete pi les in embedded wal ls.

b) Base slab - constructed from concrete cast in situ, plain orreinforced, raft or other form.

c) Roof, where applicable - constructed from reinforced in-situconcrete, precast concrete with an in-situ topping, or a steelcomposite slab, as appropriate.

NOTE 1 For structures cast entirely below ground, or where thesubstructure extends beyond the superstructure, the roof slabrequires protection against water ingress (see 6.2.1).

NOTE 2 Further guidance on construction methods for each type ofwaterproofing protection is given in Clause 8, Clause 9 and Clause 10.

l) Alternatively, a radon report can be obtained online fromhttp://www. ukradon.org.

@ 8 S 1 2 0 0 9 . 1 9


8 Type A (barrier) protection

8.1 Structural aspectsCOMMENTARY ON 8.1Structures using Type A protection are normally constructed of concreteor masonry. Deeper structures are of concrete construction Sfee/ can alsoform part of the construction as temporary sheet piling. Considerationmight be given to employing the sheet pile wall as an element of thewaterproofing system (see Clause 9).

Schematic illustrations of Type A protection are given in Figure 2a).

8.1 .1 Genera l

Barr ier protect ion design should be based on an evaluat ion of:

a) the nature of the substrate(s);

b) the l ikely overal l and local movements that might cause distress inthe waterproofing barrier;

c) the ability of the barrier system to accommodate these movements;

d) the essential characteristics of the waterproofing system,e.9. bonded/unbonded, pre-a ppl ied/post-a ppl ied, l iqu id-appl iedor pre-formed;

e) the need for external or internal appl icat ion;

f) the effects of environmental contaminants.

8.1.2 Differential movement and crackingBarr ier-specif ic propert ies should also be evaluated, al lowing for anypredicted cracking from the structure. The waterproofing barriershould be capable of providing the appropriate protect ion againstwater and water vapour without disrupt ion or decay.

Although some barr ier mater ials accept local strains and canaccommodate a crack opening in the support ing structure, i t shouldbe noted that others might be damaged by differential movement orcracking (see Figure 4).

Care should be taken so that a load-bearing substrate is capable ofsupport ing the barr ier mater ial , even under sustained water pressure,part icular ly around openings or service penetrat ions. A level l ing orsmoothing layer should be appl ied to masonry structures, as required.

NOTE There are two issues in regard to the possible influence of crackson barrier pertormance. One relates to cracks pre-existing at the time ofapplication and the ability of the se/ected syste m to initially bridge thecrack. Decisions based on the specific properties of the barrier materialwould be needed before deciding whether any such cracks requirepre-treatment. The second issue rs the ability of the selected system toaccommodate cracks that might form after application.

Remedial measures to f i l l s igni f icant voids or openings should beundertaken as the effect of sustained water pressure forcing thebarr ier mater ial into them might create a r isk of fai lure.

2 0 . @ B 5 1 2 0 0 9


Figure 4 Effect of structure on applied waterproofing barrier

Reinforced (in-situconcrete/mason ry) wal I

{

b) Unreinforced or nominallyreinforced (in-situconcrete/masonry) wal I

Key

1 Stress and crack width reduced by reinforcement

2 Likely to be compatible with most waterproofing barriers3 Stress and crack width increased by lack of reinforcement

4 Might exceed strain capacity of some waterproofing barriers ifwall cracks

8.1.3 Continuity of waterproofing barrierThe waterproof ing barr ier should, in most instances, be cont inuousaround the structure (see 5.2.4). In order to maintain the cont inui tyof the barr ier, penetrat ions through wal ls or f loors that are to beprotected (e.9. openings for services, pipes, cables) should be avoided,wherever possible. Where i t is essent ial to provide such openings,special t reatment around the penetrat ion should be provided andreference should be made to the manufacturer's instructions andspecial ist advice. Simi lar ly, where f ix ings through the barr ier arenecessary, the manufacturer's instructions should be followed.

Movement joints below ground should not be used unless unavoidable;in such cases these should be waterproofed in accordance with thema n ufacturer's instructions.

Where a waterproofing barrier is required for a structure supportedon pi led foundat ions, special considerat ion should be given to thedetai l ing so that structural cont inui ty is not compromised (see Figure 5)and reference should be made to the manufacturer's instructions.

O BSI 2009 . 21


Figure 5 Pi le to f loor slab junct ion

Key'I Floor slab

2 Pile cap, as appropriate

3 P i l e

4 Pile reinforcement

5 Slab/pile/pile cap to have integral protection and/or added internal orexternal membrane (catering for reinforcemenU see 8.1.3)

s.z Waterproofing barrier materials

8.2.1 GeneralThe waterproofing barrier used to provide Type A protection shouldbe instal led in one of the fol lowing locat ions, depending on themater ial(s) f rom which i t is formed:

a) on the exterior face of walls or slabs (external waterproofing);

b) on some external source of support (reverse waterproofing);

c) within the structure (sandwiched waterproofing);

d) on the inter ior face of per imeter wal ls ( internal waterproof ing).

Table 3 should be considered when select ing the appropriatewaterproof ing barr ier for use.

All barriers should be installed strictly in accordance with themanufacturer 's instruct ions, including any recommendations regarding:

1) protect ion from damage, fol lowing appl icat ion and curing, wherethe barr ier is appl ied external ly;

2) penetrat ions through the barr ier;

3) fixings, where these are necessary;

4) appl icat ion over joints in the substrate.

22 . @BS12009

BRITISH STANDARD

Table 3 Categories of barrier materials

BS 8102:2009

Type of barrier Description Relevant ApplicationA)standard(s)

Bonded sheet Bitumen-based, sheet membranes can 85743:1970, Can be appl ied external lymembranes be ei ther: Class A; or sandwiched.(see 8'2'2) a) cold-applied (self-adhesive); or or 858747

b) hot appl ied (" torch-on" or bondedusing a hot melt bi tumen adhesive).

Composite sheet membranes. Can be appl ied external lyor sandwiched.

Liquid appl ied There are many types of l iquid appl ied Can be appl ied external lymembranes membranes, which include one or two or sandwiched.(see 8.2.3) part systems.

Geosynthet ic These comprise bentonite with a single Can be appl ied external ly(bentonite) c lay or dual 'carr ier ' mater ial , typical ly of or sandwiched.liners (see 8.2.4) geotextile or high-density polyethylene.

Ihere are two pr incipal forms: drybentonite and pre-hydrated bentonite.

Mast ic asphalt These are appl ied in three coats as a BS EN 12970 Can be appl ied external lymembranes hot l iquid. or sandwiched.(see 8.2.5)

Cementi t ious These are appl ied as coat ings to surfaces Can be appl ied internal lycrystal l izat ion of concrete wal ls and slabs or a solut ion or external ly.slurr ies and or powder added to concrete.powders (see 8.2.6)

Cementi t ious These are general ly appl ied in mult i -mult i -coat renders, coats or slurr ies and are resistant totoppings and l iquid water but al low some watercoat ings (see 8.2.7) vapour penetrat ion.

Can be appl ied internal lyor externally.

A) See Figure 2a) and Figure 6.

Figure 6 Effect of bonded or partially bonded barriers

Key'1 Bonded barrier preventing water

from tracking from a defect in themembrane to a crack/joint in thesu pporti ng concrete wal I

NOTE lf the defect is coincidentwith a crack, the crack can berepaired with crack injection.

2 Part ia l ly bonded barr ier a l lowingwater to track from a defect

3 Defect in barrier

@ BSI 2009 . 23


8.2.2 Bonded sheet membranesCOMMENTARY ON 8.2.2Bonded sheet membranes may be pre- or post-applied to the structure.Pre-applied membranes are initially attached to enabling works in areverse waterproofing application; they subsequently become bonded topoured concrete walls and slabs.

A bonded sheet membrane should be f i rmly supported by aload-bearing structure so that external ground and water pressuresare adequately resisted.

It is important that the substructure provides a satisfactory base onwhich to apply the membrane, and therefore concrete should be freefrom r idges and indent ions and f inished to a true and even surface,preferably with a wood f loat f in ish. Br ickwork and blockwork shouldhave f lush joints.

8.2.3 Liquid applied membranes

8.2.3.1 GeneralDetai ls on the preparat ion of the substrate, appl icat ion rate, methodand curing requirements should be sought from the manufacturer.

8.2.3.2 Sandwichappl icat ions

When appl ied to the internal face of the structure, the membranemight need to be restrained against the effects of water pressure; insuch cases, the restraining element should be f i rm against the appl iedl iqu id membrane.

Suitable protect ion to the membrane should be provided.

8.2.4 Geosynthetic clay l inersCOMMENTARY ON 8.2.4Bentonite is a natural clay mineral, which has the capacity to expandwhen in contact with water forming a barrier to the transmission of waterand other liquids. Bentonite is held between two geosynthetic layers. Thebentonite forms an impervious seal and bonds to the concrete surface.

Geosynthetic clay liners are available in two forms. Dry bentonite liners relyon activation taking place on site from the absorption of the groundwateronce installed. Pre-hydrated bentonite liners are manufactured by vacuumextrusion and do not need to be hvdrated on site.

8.2.4.1 General

Bentonite-based waterproof ing should only be used where the l inerremains confined between two surfaces and cannot be left exposed.

NOTE The materials are suitable for new-build and refurbishmentapplications.

8.2.4.2 Horizontalappl icat ions

Geosynthet ic clay l iners can be laid onto compacted sub-base orbl inding concrete. The surface can be damp, but the l iner should notbe laid into standing water. The manufacturer 's advice should besought on surface preparat ion requirements.

2 4 . @ B S 1 2 0 0 9


8.2.4.3

The manufacturer should also be consulted regarding the cont inui tyof the horizontal l iner with the vert ical l iner as di f ferent opt ionsexist depending on the type of vert ical appl icat ion, i .e. pre-appl ied(see 8.2.4.3) or post-applied (see 8.2.4.4).

Vertical applications (pre-applied)

When pre-appl ied, the l iner should be f ixed to formwork or to secant,cont iguous or steel pi les or diaphragm wal ls and the concrete shouldbe poured direct ly, conf ining the l iner.

Vertical applications (post-applied)

When post-appl ied, the l iner should be nai led to the reinforcedconcrete structure. Minimal substrate preparat ion is required. As soonas possible after the vert ical bentonite sheet ing has been appl iedto the wal ls, backf i l l ing should take place in accordance with themanufacturer's instructions.

8.2.4.4

8.2.5 Mastic asphalt membranesCOMMENTARY ON 8.2.5Mastic asphalt is composed of graded mineral matter and asphalticcement in such proportions as to form a coherent, voidless, impermeablemass, solid or semi-solid under normal conditions but sufficiently fluidwhen brought to a suitable temperature to be spread by means of a handfloat or by mechanical means.

Mast ic asphalt should always be appl ied in three coats. Horizontalsurfaces to which mast ic asphalt is to be appl ied should be level andfree from irregular i t ies.

Brickwork and concrete surfaces formed using t imber shutter ingare usual ly suff ic ient ly rough to provide a key for vert ical asphalt ;however, smooth surfaces do not give an adequate key so, if thesecannot be avoided, technical advice should be sought on theappropriate treatment.

When mast ic asphalt is not ful ly conf ined, the maximum design loadshould not exceed that stated by the manufacturer to prevent extrusion.

8.2.6 Cementit ious crystall ization slurries and powdersCOMMENTARY ON 8.2.6Cementitious crystallization barriers are blends of Portland cement,treated quartz sands and active chemicals. They are supplied in powderform and are mixed with water to form a slurry, which is then applieddirectly to the prepared concrete surface.

The active chemicals combine with free lime and moisture present in thecapillary tracts to form insoluble crystalline complexes which preventwater ingress.

8.2.5.1 General

Cementi t ious crystal l izat ion barr iers should be appl ied to ei therinternal or external surfaces of the concrete structure by brush orspray. They are suitable for use on both new and existing structures,and do not require a loading coat.

O BSI 2009 . 25


Surfaces should be prepared ( in accordance with the manufacturer 'sinstruct ions) so as to have a capi l lary open structure pr ior to theappl icat ion of the barr ier.

NOTE A capillary open structure refers to the intrinsic fine capillary tracts(pore structure) of a concrete matrix.

8.2.6.2 Horizontalappl icat ions

Cementi t ious crystal l izat ion barr iers can be appl ied as a single coatslurry to hardened concrete or dry spr inkle and trowel-appl ied tofresh concrete.

They can also be appl ied to concrete bl inding immediately pr ior to theplacing of overlaying concrete.

8.2.6.3 Vert icalappl icat ions

The barr ier should be appl ied in a two-coat appl icat ion to al l vert icalsurfaces. Vertical surfaces should be prepared in accordance with thema nufacturer's instructions.

8.2.7 Cementit ious multi-coat renders, mortars and coatingsThe installation of cementitious multi-coat renders, mortars and coatingsshould, unless otherwise advised by the manufacturer, be left until asmuch as practicable of the structure's dead load has been applied.

The substrate should be prepared in accordance with the manufacturer'sinstructions prior to the application of the system.

Detai ls on the appl icat ion method and rate, mixing, number oflayers/coats and curing requirements should be sought from themanufacturer.

Existing substrates and structural elements should be assessed forsuitability to withstand any increase in applied loads from water pressure.

9 Type B (structurally integral) protection

9.1 GeneralNOTE For water and water vapour resistance, Type B protection reliesupon the design and the materials incorporated into the external shell ofthe structure itself.

Schematic illustrations of Type B protection are given in Figure 2b).

Structures providing Type B protection should be constructed ofreinforced concrete or structural steel and designed in accordancewith the relevant part of BS EN 1992 or BS EN 1993 respect ively.

Concrete structures containing a waterproof admixture should beconsidered as having a lower degree of water/vapour transmission whenthe design of the concrete mix and casting of the structure is adequatelysupervised and the admixture is assessed and certif ied (see 9.2.1.3).

Service entr ies are part icular ly vulnerable to water penetrat ion;where they cannot be avoided, they should be careful ly detai led,incorporat ing seal ing, to minimize the r isk of water ingress.

2 6 . @ B S 1 2 0 0 9


9.2 Materials for structurally integral protection

9.2.1 Concrete

9.2.1.1 GeneralNOTE 1 Reinforced concrete structures may be designed and detailedspecifically to minimize water ingress with no additional protectivemeasures. Concretes meeting minimum design requirements for structuraluse and durability in the ground, and properly placed and compacted,are likely to have good resistance to the transmission of water in liquidform. .A degree of resistance to water vapour transmission is also achieveddependent on section thickness.

The pattern of any seepage encountered is often associated with poorjoints, cracks or other discontinuities such as service penetrations.

The fol lowing factors are considered as being of part icular importancein achieving a water-resistant concrete structure and thus should betaken into account:

a) the design of the structure (general and detai led), and thespecif icat ion of mater ials;

b) the qual i ty of workmanship in preparing and placing concrete;

c) cur ing;

d) si te organizat ion;

e) the condit ion of the formation, i .e. the formation should be cleanwith no running water;

f) material storage;

g) the close-fitting of formwork, the fixing of reinforcement(s) andthe preparat ion of jo ints.

Crack widths in concrete should be control led by using the appropriatedesign, mix specif icat ion, detai l ing, construct ion supervision and curing(especial ly in relat ion to temperature).

NOTE 2 For guidance on limiting crack widths, see 8S EN 1992 and CIRIApublication C660 [8].

The effects of residual moisture ingress (water or water vapour) maybe minimized by the provision of appropriate internal environmentaldesign and control mechanisms.

When select ing appl ied internalf in ishes, advice should be soughtfrom the manufacturer. Moisture content and relat ive humidi tyshould also be considered in accordance with BS 8204-1.

9.2.1.2 Reinforced and prestressed concrete (in-situ or precast)

Structures in reinforced or prestressed concrete should be designedand constructed in accordance with BS EN 1992.

9.2.1.3 Concrete containing waterproofing admixtures

COMMENTARY ON 9.2.1.3There is a range of products, generally categorized as waterproofingadmixtures, which seek different ways to increase the inherent resistanceof concrete to water and water vapour. As the mechanisms used by eachproduct to achieve these aims are quite diverse, it is not possible in thisBritish Standard to give specific auidance on their use.

Waterproofing admixtures are specified in BS EN 934.

@ B5l 2009 . 27


Manufacturers should be consulted as to the performance of a specif icwaterproofing admixture in reducing the risk of water penetrationthrough a crack, possibly under considerable hydrostat ic pressure.Potent ial seepage locat ions, such as penetrat ions and joints, wouldtypically be addressed by design (e.9. waterstops; see 9.2.1.4').

Where the waterproofing admixture has been assessed and certifiedby a UKAS-accredited body or a European Technical Approval body,certification information should be referred to for guidance on useand the extent or l imitat ion of technical benef i t .

Waterproof ing admixtures should be used in conjunct ion with otherwaterproofing components supplied by the same manufacturer,e.g. waterstops, sealants.

9.2.'1.4 Waterstops

COMMENTARY ON 9.2.1.4The principal types of waterstops can be classified as the following.

a) Passive sections;

1) rubber or flexible polyvinyl chloride (PVC) extruded profilescast into the concrete on both sides of the joint, either at theconcrete surface or mid-depth of the concrete section, to form aphysical obstruction to water transmission;

2) steel water bar strips placed mid-depth of the concrete section toform a physical obstruction to water transmission.

b) Active or hydrophilic strips or crystallization slurries:

1) preformed profiles of materials or sealant composition appliedto the concrete joint at depth in the section. The materials swellor give rise to crystal growth on contact with water providing anenhanced obstruction. They can used as a sole material or in acomposite product with passive waterstop sections;

2) post-injected systems.

c) Permeable hose or other sections that are fixed to the constructionjoint surface before casting the second poun to facilitate the injectionof a specialist sealing resin into the joint, when required.

Waterstops should be used to provide enhanced resistance to watertransmission at jo ints in the concrete structure, e.g. at construct ionor day-work joints, services or other penetrations (see Figure 2). Theposit ioning of the waterstop(s) (external and/or internal) should beappropriate for the method of construction and the level of risk.Particular attention should be given to the use of waterstops atmovement joints (see 8.1.3).

The specifier should be satisfied that waterstops have been testedand cert i f ied for the appl icat ion, service condit ions and groundwaterchemistry proposed.

Where centre-bulb waterstops are used, robust methods of fixingshould be used to keep the components in place during concret ingoperations. Correct orientation should be provided to facilitateadequate compaction of the concrete around any internal componentsand to avoid creating paths for subsequent water ingress.

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9.2.2 Steel

Steel piles in either sheet or tubular form may be used as the permanentstructural wall in cases where the pile clutch interlock system betweenindividual sections can be adequately sealed. Soldier piles formed fromH or I sections may also be used with suitable lagging.

Steel structures should be designed and constructed in accordancewith BS EN 1993-5.

Sect ions should be formed of structural steel of a weldable gradeconforming to the fol lowing standards, as relevant:

a) BS EN 10248for hot rolled steel sheet piles;

b) BS EN 1 0249 for cold formed steel sheet piles;

c) BS EN 10210 for hot f in ished hol low sect ions; or

d) BS EN 10219 for cold f in ished hol low sect ions.

NOTE BS EN 10248 also covers special interlock sections, which areproduced to allow hollow sections to be connected together or toi ntermed i ate sheet piles.

e.3 Embedded retaining walls

9.3.1 GeneralConstruction for deep structures may be either top down or bottomup, or a combinat ion thereof. The construct ion method should, asdictated by the ground condit ions and si te constraints ( including theproximity of bui ldings on adjacent si tes), determine the use and typeof embedded pi led wal ls, which may be of concrete or steel pi le, ord iaphragm wal ls .

For al l types of embedded retaining wal l , the requirements forwater resistance should be clear ly specif ied, e.g. by using thef CE's Specification for piling and embedded retaining walls lll orequivalent guidance. ln part icular, the acceptabi l i ty of running ordr ipping water (seepage) and the extent to which any damp areas aretolerable should be considered and specif ied, as appropriate for therequired grade of waterproofing protection (see 6.2.3).

NOTE 1 Embedded retaining walls provide a degree of integralprotection, although the number of joints and difficulties controlling theirconstruction can lead to a risk of a greater quantity of water penetration,compared with a cast in form wall, and this needs to be allowed for in theovera ll desig n strategy.

For al l embedded retaining wal ls, whether concrete or steel, the jointbetween the base slab and the wal l should be precisely detai led toachieve structural cont inui ty consistent with the design. This junct ionshould be viewed as a three-dimensional arrangement (see also 4.3.1),such that al l potent ial water paths can be ident i f ied and detai led.The joint should be careful ly detai led and waterstops should beattached to, and fol low, the prof i le of the wal l in accordance with themanufacturer's i nstructions.

NOTE 2 Grouting tubes may also be installed within a clean flush joint sothat remedial grouting can be undertaken, if necessary. Attempts to installgrout tubes that maintain intimate contact with convoluted joints mightbe unsuccessful; in this situation, a hydrophilic strip bonded to the jointwith adhesive might be more suitable (see a/so Clause 11).

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9.3.2 Concrete retaining wallsPi led and d iaphragm reta in ing wal ls should conform to the generalrequi rements of BS EN 1992.

NOTE 1 The water penetration through well-formed walls using thesetechniques is normally limited to, and controlled by, the vertical jointsrather than the flow through the concrete elements and there is thus littlebenefit in designing concrete piled and diaphragm walls in accordancewith the higher tightness c/asses specified in BS EN 1992-3.

Where secant p i le reta in ing wal ls are used, specia l is t advice should beobtained as to the appropriate system and construction method forthe project.

NOTE 2 The joints between diaphragm wall panels can be enhanced bythe incorporation of water bars, where the performance requirementsjustify it. Such water bars can be effective at restricting water ingress viatransverse flow through the wall section but further attention might benecessary to deal with water flowing up the wall joints inboard of thewater bar location.

9.3.3 Steel retaining wallsThe performance level of water tightness should be specified.This may be achieved by the appl icat ion of an appropriate seal ingsystem(s) to the clutch interlocks, using one of the following systems:

a) act ive (hydrophi l ic) systems, pre-appl ied or; i f essent ial , appl iedunder shelter and t ight ly control led condit ions on si te; or

b) passive (hot-installed bituminous product) systems; or

c) welded clutches.

The system selected should be able to provide the specifiedperformance and be consistent with the method of instal l ing the pi les.

The manufacturer 's instruct ions should be fol lowed to achieve thenecessary resistance to seepage.

NOTE 1 ln some instances, welded clutches might be used in addition tothe systems specified in a) and b).

For integral protect ion, sheet pi le inter locks should be welded orsealed with a hydrophi l ic mater ial in accordance with BS EN 12053.Seal ing welds along the inter lock should be capable of accommodatingany movement that might take place. The welding process should beselected to suit the environment to which the welds are exposed andthe si te condit ions in which welding occurs.

NOTE 2 Sfee/ sheef p ile interlocks can be seal-welded after installation toprovide watertight structural walls.

The connect ion to the base slab should cater for any upl i f t forces inaddit ion to providing a robust barr ier to water ingress. Horizontalsealants should be provided at the junct ion between the base slab andthe perimeter wal l using act ive or passive methods.

Where possible, sheet pi les should be shop-welded and subsequent lydriven in sets of two or three, thus reducing the extent of site weldingrequired. l f welding is undertaken on si te, only the exposed length ofthe sheet pi les is treated. Appropriate working condit ions need to beprovided and the pi les should be dr iven within acceptable deviat ionsto form the joint .

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NOTE 3 Failure to prepare the surfaces appropriately increases the riskof porosity in the welds, with reduction in the degree of water resistanceover time.

NOTE 4 Guidance on welding is given in BS EN 101 1 andBS EN ISO 1 561 4-1 . Further guidance is also given in the ICE's Specif icationfor p i l ing and embedded reta in ing wal ls /7 / and BS EN 1993-5.

10 Type C (drained) protectionCOMMENTARY ON CLAUSE 1OType C waterproofing protection manages water that penetrates theexternal shell of a structure, by collecting it in a cavity formed betweenthe erternal wall and an internal lininglwall. There is permanent relianceon this cavity to collect groundwater seepage and direct it to a suitabledischarge point, e.g. drains or a sump for removal by gravity drainage ormechanical pumping.

New construction generally incorporates a cavity drain membrane.Howeve4 the use of other products and techniques, such as drained voidsconstructed in masonry, can also be considered. Traditionally, the cavity infloor construction has been formed by the use of either no-fines concreteor ceramic tile systems. These are rarely used in new construction, butmight be encountered when refurbishing existing structures (see 5.2.3).

Schematic illustrations of Type C protection are given in Figure 2c).

10.1 Structural aspectsThe outer leaf of the exter ior wal l should be capable of control l ingthe quantity of water that can pass through it, in order not to exceedthe drainage capacity of the system. Water enter ing a drained cavitysystem is regulated by the structure, so defects that might result inunacceptable leaks should be remedied before the system is instal led.

10.2 Cavity drain systemsNOTE Cavity drain systems do not change the loadings due to water onan existing structure, other than where remedial measures are taken tocontrol water inqress.

10.2.1 Cavity drain systems with membranes

10.2.1.'l Cavity drain membranesNOTE Where cavity drain membranes are used, the membrane forms apermanent cavity between the external elements of the structure and theinternal walllfloor finishes. Such cavities vary in width, depending on thestud height or profile of the membrane, but are usually up to 20 mm.

Cavity drain membranes should be used in accordance with themanufacturer 's instruct ions. In part icular, the stud height or prof i leof the membrane should be selected in conjunct ion with themanufacturer's data and after considering the external hydrostaticpressure, the porosity of the structure and the predicted rates ofwater ingress though the structure's external fabr ic.

Cavity drain membranes can be used on surfaces that have beencontaminated with impurities. Howeve4 in these situations, consultationshould be undertaken with the local environmental agency regardingdischarge from the system.

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Before a cavi ty drain membrane is laid or f i t ted on wal ls and f loorsconstructed of new concrete, the concrete surface should be treatedto reduce the r isk of leaching of f ree l ime or mineral sal ts and to avoidthe obstruct ion of the drainage system.

'10.2.1.2 Floorcavit ies

Where the f loor cavi ty incorporates perimeter channels that dischargeinto a sump(s), both the channels and the sump(s) should be cleanedbefore, dur ing and after instal lat ion of the membrane to al lowuninterrupted drainage (see also 10.3).

Before the cavi ty drain membrane is laid:

a) the f loor should be f lood tested to conf irm that al l water runsfreely to the points of col lect ion; and

b) the base slab should be cleaned to remove al l debris that mightcause blockages.

Sect ions of the membrane(s) laid across the f loor should be jointedand sealeo.

Once laid, the membrane should be protected against damage causedby fol lowing trades.

The membrane should be inspected for damage and any defectsshould be remedied before f loor f in ishes are appl ied.

NOTE The cavity drain membrane may be covered with a variety of floorfinishes dependent on the design requirements of the structure.

10.2.1.3 Wal lcavi t ies

The wal l cavi ty should be constructed so that i t remains free drainingat a l l t imes.

Where the wal l cavi ty incorporates perimeter channels that work inconjunct ion with a drained f loor cavi ty, the drainage, which is commonto wal ls and f loors, should conform to 10.2.1.2.

Before the cavity drain membrane is fitted, in situations where the cavityis to be constructed or installed over existing walls, all wall coveringsthat might decay, or become loose or friable, should be removed.

NOTE I lf they are not removed, such wall coverings can cause theblockage of the cavity or drainage channels and impede free drainage.

Sect ions of the membrane(s) f i t ted to the wal ls should be jointed andsealed ensuring adequate laps.

NOTE 2 The cavity drain membrane may be covered with a variety ofwall finishes dependent on the design requirements of the structure.

10.2.2 Cavity drain systems without membranesWhere a drained cavity is formed by a masonry cavity wall, theinner leaf should be ei ther bui l t of f a concrete upstand, constructedintegral ly with the slab, or bui l t of engineering br icks to a minimumof 150 mm above channel level.

Mater ials should be selected which are appropriate to theenvironment on both faces.

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Where the cavi ty is constructed against an embedded retaining wal l ,al lowance should be made for the permit ted construct ion tolerances,in order to maintain the necessary channel width.

Care should be taken during construct ion to keep the cavi ty clear ofdebris and mortar droppings.

In order to al low free drainage from the channel and access formaintenance, i t is recommended that this channel is la id nominal lylevel but with adequate access points for maintenance through theinner leaf of the cavi ty wal l . Where possible, the drainage channelshould be formed within the depth of the slab. Where this cannotbe achieved, the detai l ing should be such that water cannot migratefrom the cavity across the slab.

A drained cavity to the roof should be considered either as part of thebase construction or, where necessary, as part of the remedial measures.

'10.2.3 Cavity ventilationIt is not usually advisable to ventilate the cavity; however, it might benecessary in certain circumstances, such as where there is a potentialfor radon, methane or other ground gases and contaminants to bepresent. In these circumstances, special ist advice should be soughtduring the design phase.

10.3 Maintenanceand commissioning

'10.3.1 DesignIn order to maximize the long-term integrity and effectivenessof a waterproofing system incorporating Type C protection, thewaterproof ing system should be designed to be maintainable.

Access points that al low rout ine maintenance of channels and out letsshould be incorporated into the design of the waterproof ing system.

10.3.2 Installation and inspectionlmmediately after the instal lat ion of a cavi ty drain system, drainagechannels and sumps should be cleared out and tested. Pumping devicesshould be checked, tested and ful ly commissioned in accordance withthe manufacturer's instructions.

NOTE ln circumstances where pumps are running for long periods oftime, or where the system is subject to silting or the deposition of freelime, more frequent servicing might be necessary.

The servicing requirements for the waterproof ing system should beclearly set out in the documentat ion suppl ied by the designer to thecl ient, including the need for regular planned maintenance of thedrainage and/or pumping systems not less than once a year.

The cl ient should be informed that any fai lure to adhere to themaintenance schedule could result in a fai lure of the waterproof ingsystem.

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11 Remedial measures

11.' l GeneralNOTE There are many causes of seepage in new and existing structures,principally poor design andlor specification, defective materials, defectiveworkmanship, deterioration of the structure, or a change in the externalenvironment (e.9. rising groundwater or locally leaking sewers or watermains). Adjacent construction works can also affect the pattern ofgroundwater flow and surface water run-off. ,A number of these factorscan also combine fo cause problems.

Before any remedial act ion is taken, defects should be diagnosed todetermine the cause and extent of fai lure. The correct diagnosis of thefault is of vital importance, to establish whether faults exist with thesystem as a whole, or whether faul ts are local ized (see also 5.2).

Where remedialwork is required, the fol lowing measures shouldbe considered:

a) the instal lat ion of a tanking system or a drained cavity;

b) the instal lat ion of external drainage; or

c) local ized works to the fabr ic of the structure. such as:

1) pressure or vacuum grout ing (see 11.2);

2) crack seal ing with resin or cementi t ious mortar (see 11.3);

3) crack f i l l ing by pressure or vacuum inject ion (see 11.4);

4) the replacement of local ly defect ive mater ial (see 11.5).

These should be considered irrespect ive of whether planned remedialtreatment has been included as a cont ingency measure in newconstruct ion or for maintaining or improving the internal environmentof an exist ing structure.

Repairs to concrete should be carr ied out in accordance with therelevant part(s) of BS EN 1504.

COMMENTARY ON 11.1lf the location of a defect in an existing external membrane can beestablished, it is possible in some instances, where access rs not a problem,fo expose the membrane and carry out repairs by excavating locally,adjacent to the walls of the structure.

Where the internal membrane is fully bonded to the substrate, the defectis generally located at the position where dampness or seepage occurs.Once the internal finish has been removed to reveal the defect, themembrane can be locally repaired using compatible materials.

Where the internal membrane is only partially bonded to the substrate,the defect might be more difficult to locate. Even if the defect can befound, further migration to other defects can follow. ln such cases,consideration needs to be given to removing and replacing the entiremembrane with a new bonded system.

Locating defects in a sandwich system can be particularly problematic andlocalized repair is seldom viable.

Where access rs not feasible, grouting in accordance with 11.2 and 11.4ought to be considered.

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11.2 Pressure or vacuum groutingGrouting to cut off seepage might repair isolated defects. Howeve4it should be noted that, where a large number of defects occur, it ismore effective to prevent water ingress by other methods.

There are a number of grout ing mater ials avai lable for use based on:

a) cement;

b) bentonite;

c) chemical (e.9. acryl ic) ;

d) resin (e.9. epoxide, polyester and non-expansive polyurethane);

e) expansivepolyurethane;

f) modified rubber latex.

Holes should be dr i l led through the wal ls and f loor of the structureadjacent to the defect (sometimes inclined to intersect seepage paths)and the pressure or vacuum grout should be dr iven into the mater ialbehind to gel and seal the leak. As grout select ion and appl icat ion arespecial ized techniques, advice should be sought from manufacturersand experienced appl icators pr ior to use.

NOTE Often more than one phase of grouting is needed as theseepage might be moved to defects elsewhere in the structure or higherup in the walls.

Care should be taken when grout ing larger areas to avoid blockingany external drainage systems.

11.3 Crack sealing with resin or cementitious mortarWhere structural cont inui ty is not required and there is no hydrostat icpressure against the adhesion of the repair ; cement grout, neatcement grout or low viscosity latex emulsion should be brushed intocracks and porous areas to seal them against water ingress.

Suitable mater ials include:

a) cementi t iousslurry;

b) cemenVsi l ica-fume slurry;

c) polymer-modif ied cementi t ious slurry;

d) polymer resin;

e) cementitious crystallization systems;

f) epoxide putty.

1't.4 Crack fil l ing by pressure or vacuum injectionPressure or vacuum in ject ion can be used to f i l l and seal cracks andjo ints , par t icu lar ly at k ickers where a waterstop has become displacedand cut t ing out and replacement is not pract ica l .

NOTE 1 Porous areas of concrete can sometimes be injected successfully,but severe honeycombing might require the defect to be cut out andreplaced.

NOTE 2 lnjection techniques have been used to seal very fine cracks.

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The selection of grout systems should take into account:

a) the l ikel ihood of structural movement;

b) the nature and size of the defect;

c) the moisture content of the substrate;

d) the temperature of the structure;

e) the injection method to be used.

Where the wall or floor is expected to remain damp, a water-tolerantgrout should be used. Suitable mater ials include:

1) epoxy resin;

2) polyurethane resin;

3) acryl ic resin;

4) polyester resin;

5) styrene-butadiene rubber (SBR) and acryl ic emulsions;

6) polymer-modified cementitious grouts.

11.s Replacement of locally defective materialNOTE 1 Where a relatively small number of well-separated defects inthe walls or floors result in seepage (e.9. poorly compacted concrete),adequate repairs can be achieved by cutting out and replacing thedefective area. Achieving a water-resistant joint between the substrateconcrete and the repair material is the most critical feature of thismethod. The installation of temporary drainage points, in the area to berepaired, might be necessary in some situations to control the seepage.However, some repair materials are formulated for application whererunning water is present.

NOTE 2 Surface preparation and the compatibility of the physical andchemical properties of the repair material are important. Many types ofrepair materials are available, including:

a) concrete compatible with that used in the original construction;

b) polymer-modified cementitious mortars and concrete;

c) polymer-basedmortars;

d) sprayed concrete.

The propert ies of the repai r mater ia l should be selected to matchthe substrate as c losely as possib le, par t icu lar ly the shr inkage andthermal behaviour . Specia l is t advice should be obta ined to selectthe most suitable concrete repair system and to specify the requiredperformance of the mater ia l to sui t the s ize, depth and locat ion of thearea to be repai red.

Where proprietary mortars or concretes are used, they should beappl ied in accordance wi th the manufacturer 's inst ruct ions, and anyrepair should be undertaken by exper ienced contractors.

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BRlTISH STANDARD BS 8102:2009

Bibl iography

Standards publ icationsFor dated references, only the edition cited applies. For undatedreferences, the latest edi t ion of the referenced document ( includingany amendments) appl ies.

BS 5454, Recommendations for the storage and exhibition of archivaldocuments

BS 8485, Code of practice for the characterization and remediationfrom ground gas in affected developments

BS EN 934, Admixtures for concrete, mortar and grout

BS EN 752, Drain and sewer systems outside buildings

BS EN 101 1, Welding - Recommendations for welding of metallicmaterials

BS EN 1 992-3, Eurocode 2: Design of concrete structures - Part 3:Liquid retaining and containment structures

BS EN ISO 15614-1, Specification and qualif ication of weldingprocedures for metallic materials - Welding procedure test - Part 1: Arcand gas welding of stee/s and arc welding of nickel and nickel alloys

Other publications

t1l INSTITUTE OF CIVIL ENGINEERS. Specification for piling andembedded retaining wal/s. Second edition. London: ThomasTelford Publ ishing, 2007.

T21 GABA, A.R., SIMPSON, 8., POWRIE, R. AND BEADMAN, D.R.Embedded retaining walls - Guidance for economic desrgn. C580.London:C lR lA, 2003.

t31 GREAT BRITAIN. Bui lding Regulat ions 2000 and subsequentamendments. London: The Stat ionery Off ice.

GREAT BRITAIN. Bui lding (Scot land) Regulat ions 2004, asamended. Edinburgh: The Stat ionery Off ice.

GREAT BRITAIN. Bui lding Regulat ions (Northern l reland) 2000, asamended. London: The Stat ionery Off ice.

l4l BUILDING RESEARCH ESTABLISHMENT. Radon - Guidance onprotective measures for new buildings. BR21 1. Watford: BREPress, 2007.

tsl BUILDING RESEARCH ESTABLISHMENT. Radon - Guidance onprotective measures for new dwellings in Scotland.8R376.Watford: BRE Press, 1999.

t5l BUILDING RESEARCH ESTABLISHMENT. Radon -Guidance onprotective measures for new dwellings in Northern Ireland.BR413. Watford: BRE Press, 2001.

O B5l 2009 . 37


l7 l GREEN, B.M.R., MILES, J.C.H. AND REES, D.M. Radon in Dwel l ingsin Scotland: 2008 Review and Atlas. HPA-RPD-051. Didcot: HealthProtection Agency, 2009. 2)

t8l BAMFORTH, P.B. Early-age thermal crack control in concrete.C660. London: ClRlA, 2007.

Further readingBS EN 1991, Eurocode 1 : Actions on structures

BS EN 1996, Eurocode 6: Design of masonry structures

BS EN 13252, Geotextiles and geotextile-related products -Characteristics required for use in drainage systems

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2) Avai lable f rom www.hpa.org.uk.

Documents

BS 8102 2009 - ScandiProof.com