ID PreparationSitesResistanceMoisture4 2000724 SH

8/12/2019 ID PreparationSitesResistanceMoisture4 2000724 SH

1/22

Part 4

Preparation of Sites and Resistance to Moisture

The Building Bye-Laws (Jersey) 1997. Code of Practice

TECHNICAL GUIDANCE DOCUMENT

States of JerseyPlanning and Environment Committee


2/22

PAGE

USE OF GUIDANCE 2

PREPARATION OF SITES ANDRESISTANCE TO MOISTURE

THE REQUIREMENTS 3

GUIDANCEPerformance 4Introduction 4Definitions 4

Section 1: Site preparation andsite drainage 6

Normal site preparation 6Organic material 6Site drainage 6

Section 2: Contaminants 7

Signs of contaminants 7Alternative approach 8Gaseous contaminants 8Radon 8Landfill gas and methane 8General approach 8References 10

Section 3: Floors next to the ground 11

Ground supported floors 11

Suspended timber ground floors 13Suspended concrete ground floors 14

Section 4: Walls 15

Internal and external walls (moisture fromthe ground) 15Additional provision for external walls(moisture from the outside) 16Cavity external walls 16

Section 5: Cladding for external wallsand roofs 18

Standards referred to 20

PAGE

DIAGRAMS1. Floor, resistance to moisture 42. Wall, resistance to moisture 43. Roof, resistance to moisture 4

4. Subsoil drain cut during excavation 65. Ground supported floor principle 116. Ground supported floor construction 117. Suspended timber floor principle 138. Suspended timber floor construction 149. Suspended floor preventing water

collection 1410. Suspended concrete ground floor 1411. Walls principle 1512. Damp-proof courses 1513. Protecting inner leaf 1514. Insulated external walls examples 1715. Cladding principle 1816. Cladding of walls and roofs 18

TABLES1. Sites likely to contain contaminants 72. Possible contaminants and actions 7

Technical Guidance Document Preparation of Sites and Resistance to Moisture

1

Contents


3/22

THE TECHNICAL GUIDANCEDOCUMENTS

The Building Bye-Laws (Jersey) 1997, which comeinto operation on the twentieth day of February1997, replace the Building Bye-Laws (Jersey) 1960and consolidate all subsequent revisions to thoseBye-Laws. This document is one of a series thathas been approved by the Committee as practicalguidance on meeting the requirements of the secondschedule and Bye-Law 7 of the Building Bye-Laws(Jersey) 1997.

At the back of this document is a list of thosedocuments currently published which have beenapproved for the purpose of the Building Bye-Laws.

The detailed provisions contained in the TechnicalGuidance Documents are intended to provideguidance for some of the more common buildingsituations. In other circumstances, alternative waysof demonstrating compliance with the requirementsmay be appropriate.

Evidence supporting compliance

There is no obligation to adopt any particularsolution contained in a Technical GuidanceDocument if you prefer to meet the relevantrequirement in some other way. However, should

a contravention of a requirement be alleged then, ifyou have followed the guidance in the relevantTechnical Guidance Documents, that will beevidence tending to show that you have compliedwith the Bye-Laws. If you have not followed theguidance then that will be evidence tending to showthat you have not complied. It will then be for you todemonstrate by other means that you have satisfiedthe requirement.

Other requirements

The guidance contained in a Technical Guidance

Documents relates only to the particular requirementsof the Bye-Laws which that document addresses.The building work will also have to comply with therequirements of any other relevant paragraphs in thesecond schedule to the Bye-Laws. There areTechnical Guidance Documents which give guidanceon each of the other requirements in the secondschedule and on Bye-Law 7.

LIMITATION ON REQUIREMENTS

In accordance with Bye-Law 8, the requirements inparts 1, 2, 3, 4, 5, 6, 7, 9 and 10 of the second

schedule to the Building Bye-Laws do not requireanything to be done except for the purpose ofsecuring reasonable standards of health and safetyfor persons in or about the building.

MATERIALS AND WORKMANSHIP

Any building work which is subject to requirementsimposed by the second schedule to the BuildingBye-Laws should, in accordance with Bye-Law 7,

be carried out with proper materials and in aworkmanlike manner.

You may show that you have compiled with Bye-Law7 in a number of ways, for example by theappropriate use of a product bearing an EC mark inaccordance with the Construction Products Directive(89/106/EEC), or by following an appropriatetechnical specification (as defined in that Directive),a British Standard, a British Board of AgrmentCertificate, or an alternative national technicalspecification of any member state of the EuropeanCommunity which, in use, is equivalent. You will find

further guidance in the Technical GuidanceDocument supporting Bye-Law 7 on materials andworkmanship.

Technical specificationsBuilding Bye-Laws are made for specific purposes;health and safety, energy conservation and thewelfare and convenience of disabled people.Standards and technical approvals are relevantguidance to the extent that they relate to theseconsiderations. However, they may also address

other aspects of performance such as serviceabilityor aspects which although they relate to health andsafety are not covered by the Bye-Laws.

When a Technical Guidance Document makesreference to a named standard, the relevant versionof the standard is the one listed at the end of thepublication. However, if this version of the standardhas been revised or updated by the issuingstandards body, the new version may be used as asource of guidance provided it continues to addressthe relevant requirements of the Bye-Laws.

Preparation of Sites and Resistance to Moisture Technical Guidance Document

2

Use of GuidanceTHE BUILDING BYE-LAWS (JERSEY) 1997


4/22

This Technical Guidance Document which takes effecton 20 February 1997, deals with the following require-ments from Part 4 of the second schedule to theBuilding Bye-Laws (Jersey) 1997.


3

The Requirements

Requirement Limits on application

SITE PREPARATION AND RESISTANCE TO MOISTURE

Preparation of site.

(10) The ground to be covered by the building shall be reasonably clear

of organic matter.

Dangerous and offensive substances..

(11) Precautions shall be taken to avoid danger to health or safety

caused by substances found on or in the ground to be covered by

the building.

Subsoil drainage.

(12) Subsoil drainage shall be provided if it is needed to avoid

(a) the passage of ground moisture to the interior of the

building; and

(b) damage to the building.

Resistance to weather and ground moisture.

(13) The walls, floors and roof of the building shall resist the passage

of moisture to the interior of the building.

Requirements (10), (12) and (13) do

not apply to a building to be used

wholly for

(a) storing goods or accommodating

plant or machinery, provided that any

persons who are habitually employed

in the building are engaged only in

storing, caring for or moving goods,

plant or machinery; or

a purpose such that

compliance with the provisions of

those requirements would not serve to

increase protection to the health orsafety of any person habitually

employed in the building; or

non-compliance with the provisions of

those requirements would not cause

damage to the fabric of the building.


5/22

Performance

In the view of the Committee the requirements 10,11 and 12 of part 4 will be met by taking precautionsto reduce risks to the health and safety of persons in

buildings by safeguarding them and the buildingsagainst the adverse effects of:

a. vegetable matter, and

b. contaminants on or in the ground to be coveredby the building, and

c. ground water.

In the view of the Committee requirement 13 ofpart 4 will be met by:

a. a floor next to the ground preventing unduemoisture from reaching the upper surface of the floor

(see Diagram 1);

b. a wall preventing undue moisture from theground reaching the inside of the building, and, if it isan outside wall, adequately resisting the penetrationof rain and snow to the inside of the building (seeDiagram 2);

c. a roof resisting the penetration of moisture fromrain or snow to the inside of the building (seeDiagram 3);

d. ensuring that floors next to the ground, wallsand roof are not damaged by moisture from the

ground, rain or snow and do not carry that moistureto any part of the building which it would damage.

Damage can be avoided either by preventingmoisture from getting to materials which would bedamaged or by using materials which will not bedamaged.

This document does not give guidance on preventingdamage resulting from the condensation of watervapour on cold surfaces. Technical GuidanceDocuments for part 5 (Ventilation) and part 11(Conversation of Fuel and Power should be referredto and also the BRE publication. Thermal insulation:avoiding risks.


4

Guidance

Diagram 1 Floor, resistance to moisture

Diagram 2 Wall, resistance to moisture

Diagram 3 Roof, resistance to moisture


6/22

Introduction

0.1 Section 1 of this document deals withpreparation of sites and site drainage. Section 2deals with contaminants.

0.2 Section 3 deals with floors next to the ground;Section 4 deals with walls; Section 5 deals with

cladding for external walls and roofs.0.3 There are several references in this documentto moisture damage. The damage in question isdamage so serious that it would producedeterioration in a material or structure to the pointthat it would present an imminent danger to health orsafety or (if it is an insulating material) itsperformance would be permanently reduced.

Definitions0.4 The following meanings apply to termsthroughout this Technical Guidance document.

Floor Lower surface of any space in a buildingincluding finishes that are laid as part of thepermanent construction.

Wall Vertical construction that includes piers,columns and parapets. It also includes chimneys ifthey are attached to the building. It does not includewindows, doors or similar openings.

Moisture Water in the form of a vapour as well as aliquid.

Contaminant Any material in or on the ground to becovered by the building (including faecal or animal

matter) and any substance which is, or couldbecome: toxic, corrosive, explosive, flammable orradioactive, and so likely to be a danger to healthand safety.


5


7/22

SITE PREPARATION AND SITEDRAINAGE

Normal site preparation1.1 A building will meet the performance ifprovisions are made at least to the extent describedin this Section.

Organic material1.2 Turf and other vegetable matter should beremoved from the ground to be covered by thebuilding at least to a depth sufficient to prevent latergrowth.

1.3 Building services such as below-grounddrainage should be sufficiently robust or flexible toaccommodate the presence of any roots. Jointsshould be made so that roots will not penetrate them.

Site drainage1.4 The provisions which follow assume that thesite of the building is not subject to flooding or, it if is,that appropriate steps are being taken.

1.5 Where the water table can rise to within 0.25mof the lowest floor of the building, or where surfacewater could enter or adversely affect the buildingeither the ground to be covered by the buildingshould be drained by gravity or other effectivemeans of safeguarding the building should be taken.(see alternative Approach para 1.7).

1.6 If an active subsoil drain is cut duringexcavation it should:

a. if it is to pass through the building be re-laid inpipes with sealed joints and have access pointsoutside the building, or

b. be re-routed around the building, or

c. be re-run to another outfall. (see Diagram 4). Alternative approach1.7 The performance will be met if, as analternative to providing or re-routing subsoildrainage, the building is designed and constructed

to prevent the passage of ground and surface waterto the inside or to materials which would beadversely affected by it. (see Sections 3-5Resistance to weather and ground moisture).


6

Section 1

Diagram 4 Subsoil drain cutduring excavation


8/22

CONTAMINANTS

2.1 In addition to solid and liquid contaminantsarising out of a previous use of land, problems canarise due to gases (see paragraph 0.4 for the

meaning of contaminant).

Natural contamination by the radioactive gas radonand its decay products can be a problem (seeparagraph 2.7).

The burial of waste in landfills can give rise tosubstantial quantities of landfill gas (seeparagraph 2.8).

Signs of contaminants2.2 Sites where the ground to be covered by thebuilding is likely to contain contaminants may beidentified at an early stage from planning records orfrom local knowledge of previous uses. Examples ofsuch sites are given in Table 1. However, there maybe occasions when a site has not be identified andthe presence of contaminants is only suspectedlater. Some signs of the possible presence ofcontaminants are given in Table 2.

Note that the ground to be covered by a buildingincludes the ground to be covered by its foundations.

2.3 If any signs of possible contaminants arepresent the Environmental Health Officer should betold at once. If he confirms the presence of any ofthe contaminants listed in Table 2 the relevantactions described will meet the performance. Theseactions assume that the ground to be covered by the

building will have at least 100mm of insitu concretelaid over it. See also Alternative approach,paragraphs 2.5 and 2.6.


7

Section 2

Table 1 Sites likely to containcontaminants

Chemical worksGas works

Industries making or using wood preservativesLandfill and other waste disposal sitesOil storage and distribution sitesPaper and printing worksScrap yardsSewage works, sewage farms and sludge disposal sites

Table 2 Possible contaminants and actions

Signs of possible contaminants Possible contaminant Relevant Action

MetalsMetal compounds* None

Vegetation (absence, poor or unnatural growth)Organic compoundsGases Removal

MetalsMetal compounds* None

Oily and tarry wastes Removal, filling or sealing

Asbestos (loose) Filling or sealing

Other mineral fibres NoneOrganic compoundsincluding phenols Removal or filling

Combustible material includingcoal and coke dust Removal or filling

Refuse and waste Total removal or see guidance

Flammable explosive and asphyxiating gasesincluding methane and carbon dioxide Removal

Corrosive liquids Removal, filling or sealing

Faecal animal and vegetablematter (biologically active) Removal or filling

Drums and Containers Various Removal with all

(whether full or empty) contaminated ground

Note Liquid and gaseous contaminants are mobile and the ground covered by the building can be affected by such contaminants fromelsewhere. Some guidance on landfill gas and radon is given in this document; other liquids and gases should be referred to a specialist.* Special cement may be needed with sulphates

Surface materials (unusual colours andcontours may indicate wastes and residues)

Fumes and odours (may indicate organicchemicals at very low concentrations)


9/22

2.4 Terms used in Table have the followingmeaning:

Removal means that the contaminant itself and anycontaminated ground to be covered by the buildingshould be taken out to a depth of 1m below the levelof the lowest floor and taken away.

Filling means that the ground to be covered by thebuilding is to be covered to a depth of 1m with amaterial which will not react adversely with anycontaminant remaining and will be suitable formaking up levels. The type of filling and the designof the ground floor should be considered together.Combustible material should be adequatelycompacted to avoid combustion.

Sealing means that a suitable imperforate barrier islaid between the contaminant and the building andsealed at the joints, around the edges and at theservice entries. Note that polyethylene may not be

suitable if the contaminant is a liquid such as a tarrywaste of organic solvent.

Alternative approach2.5 In the most hazardous conditions only the totalremoval of contaminants from the ground to becovered by the building can provide a completeremedy. In other cases remedial measures canreduce the risks to acceptable levels. Thesemeasures should only be undertaken with thebenefit of expert advice.

Where the actions described would, for example,

involve the removal and handling of large quantitiesof material, remedial measures which will achievecompliance with the Bye-Laws may be possible, butthey should only be undertaken with the benefit ofexpert advice.

2.6 The BS Draft for Development DD 175: 1988Code of practice for the identification of potentiallycontaminated land and its investigationgivesguidance on site investigation and further informationon sites in general is given in BS 5930: 1981 Codeof practice for site investigations.

Gaseous contaminants

Radon2.7 Radon is a naturally-occurring, radioactive,colourless and odourless gas which is formed insmall quantities by radioactive decay whereveruranium and radium are found. It can move throughthe subsoil and so into buildings. Exposure to highlevels for long periods increases the risk ofdeveloping lung cancer. Where a house is to beerected, guidance contained in the report Radon:

Guidance on Protective Measures for NewDwellings, published by the Building ResearchEstablishment should be followed.

Landfill gas and methane2.8 Landfill gas is generated by the action ofanaerobic micro-organisms on biodegradablematerial and generally consists of methane andcarbon dioxide with small quantities of other gases.It can migrate under pressure through the subsoiland through cracks and fissures into buildings.

Gases similar to landfill gas can also arise naturallyand should be treated in the same way as thosearising from landfills.

Methane is an asphyxiant, will burn, and canexplode in air. Carbon dioxide is non-flammable andtoxic. Many of the other components of landfill gasare flammable and some are toxic.

General approach2.9 Where the ground to be covered by a buildingis on, or within 250m of, landfill, or where there isreason to suspect that there may be gaseous

contamination of the ground or where the buildingwill be within the likely sphere of influence of alandfill where gas production is possible, furtherinvestigation should be made to determine what, ifany, protective measures are necessary.

2.10 Guidance on the construction of some buildingsnear but not on landfill sites has been published bythe Building Research Establishment as a Report.For such buildings the BRE guidance can befollowed. The broad guidelines for dwellings are:

a. Where the level of methane in the ground isunlikely to exceed 1% by volume and the

construction of the ground floor of a house of similarsmall building is of suspended concrete andventilated as described in the BRE publication, nofurther protection needs to be provided.

b. The concentration of carbon dioxide must alsobe considered and should be judged independentlyof the methane concentration. A carbon dioxideconcentration of greater than 11/2% by volume in theground indicates a need to consider possiblemeasures to prevent gas ingress. A 5% by volumelevel in the ground implies that specific designmeasures are required.

c. The use of permanent continuous mechanicalventilation to ensure that methane or carbon dioxidedoes not accumulate at any time in or under a houseis not usually feasible since there is no managementsystem to look after it. Passive protection isgenerally the only viable alternative and is effectiveonly where gas concentrations in the ground are lowand likely to remain so.


8


10/22


9

2.11 In other cases and for non-domestic buildings,expert advice should be sought. If the expert soadvises, there should be a complete investigationinto the nature of any hazardous gases and theirsource and the potential of the landfill site for futuregas generation.

The amount of gas in the ground as well as its

pressure relative to atmosphere also needs to beconsidered. A low level of gas due to the presence ofa small quantity of material or associated withprevious control measures may need no remedialmeasures. High gas concentrations have less impactif the volume of gas is very small such as fromlimited deposits of peat, silt etc.

The investigation together with expert advice shouldbe used to assess the present and future risk posedby the gas and should include extended monitoring,if necessary. Design of protective measures should

be incorporated into the overall design of thebuilding with the detailed assistance of experts in thefield and satisfactory arrangements should be madefor maintenance and monitoring.

Information and guidance on the site investigationare given in the documents listed in paragraph 2.12.


11/22

References2.12

a. Department of Environment (Her MajestysInspectorate of Pollution). The Control of LandfillGas, Waste Management Paper No. 27 (1989),HMSO.

b. British Standards Institution Draft for

Development: Code of Practice for the Identificationof Potentially Contaminated Land and itsInvestigationDD 175: 1988.

c. Crowhurst, D. Measurement of gas emissionsfrom contaminated land. BRE Report 1987. HMSOISBN 0 85125 246 X.

d. ICRCL 17/78 Notes on the development andafter-use of landfill sites. 8th edition December 1990.Interdepartmental Committee on the Redevelopmentof Contaminated Land.*

e. ICRCL 59/83 Guidance on the assessment and

redevelopment of contaminated land. 2nd editionJuly 1987. Interdepartmental Committee on theRedevelopment of Contaminated Land.*

f. Institute of Wastes Management. Monitoring ofLandfill GasSept. 1989.

g. BS 5930: 1981 Code of practice for siteinvestigations.

h. BRE Radon: guidance on protective measuresfor new dwellings.BRE Report. Garston, BRE, 1991. ISBN 0 85125 5116.

j. BRE Construction of new buildings on gas

contaminated land.BRE Report. Garston, BRE, 1991. ISBN 0 85125 5132.

* Obtainable from: Department of EnvironmentPublication Sales Unit, Building 1 Victoria Road,South Ruislip, Middlesex HA4 0NZ.


10


12/22


11

FLOORS NEXT TO THE GROUND

3.1 This Section gives guidance for threetypes of ground floor:

a. ground supported floors (see paragraphs3.3 to 3.8).

b. suspended timber floors (see paragraphs3.9 to 3.11).

c. suspended concrete floors (see paragraphs3.12 to 3.14).

Refer to paragraph 0.4 for the meaning of floor.

3.2 A floor next to the ground should:

a. resist ground moisture from reaching the uppersurface of the floor (see Diagram 5).

b. not be damaged by moisture from the ground.

Ground supported floors

3.3 Any ground supported floor will meet theperformance if the ground is covered with denseconcrete laid on a hardcore bed and a damp-proofmembrane is provided. Insulation may beincorporated.

Section 3

Diagram 5 Ground supported floor principle

Diagram 6 Ground supported floor

construction


13/22

Technical solution3.4 A concrete ground supported floor may be builtas follows (see diagram 6) (unless it is subjected towater pressure, in which case see Alternativeapproach, paragraph 3.8):

a. hardcore bed of clean broken brick or similarinert material, free from materials including

water-soluble sulphates in quantities which coulddamage the concrete, and

b. concrete at least 100mm thick (but thicker if thestructural design requires) and composed of 50kg ofcement to not more than 0.11m3 of fine aggregateand 0.16m3 of coarse aggregate or BS 5328 mixST2. If there is embedded steel, the concrete shouldbe composed of 50kg of cement to not more than0.08m3 of fine aggregate and 0.13m3 of coarseaggregate or BS 5328 mix ST4, and

c. damp-proof membrane above or below theconcrete, and continuous with the damp-proof

courses in walls, piers and the like.

3.5 A membrane laid below the concreteshould be at least 300m (1200 gauge); 250m(1000 gauge) polythene in accordance withappropriate BBA certificate or to the PIFAstandard is also satisfactory.

3.6 A membrane laid above the concrete should beeither polyethylene sheet as described above (butwithout the bedding material) or three coats of coldapplied bitumen solution or similar moisture andwater-vapour resisting material. In each case it

should be protected either by a screed or a floorfinish, unless the membrane is pitchmastic or similarmaterial which will also serve as a floor finish.

3.7 A timber floor finish laid directly on concretemay be bedded in a material which may also serveas a damp-proof membrane. Timber fillets laid in theconcrete as a fixing for a floor finish should betreated with an effective preservative unless they areabove the damp-proof membrane. Somepreservative treatments are described in BS 1282:1975 Guide to the choice, use and application ofwood preservatives.

Alternative approach3.8 The performance (see paragraph 0.4 above)can also be achieved by following the relevantrecommendations of Clause 11 of CP 102: 1973Protection of buildings against water from theground. BS 8102: 1990 Code of practice forprotection of structures against water from thegroundincludes recommendations for floors subject

to water pressure.


12


14/22


13

Suspended timber ground floors

3.9 Any suspended timber floor next to the groundwill meet the performance if:

a. the ground is covered so as to resist moistureand prevent plant growth, and

b. there is a ventilated air space between the

ground covering and the timber, and

c. there are damp-proof courses between thetimber and any material which can carry moisturefrom the ground (see diagram 7).

Technical solution3.10 A suspended timber floor next to the groundmay be built as follows (see Diagram 8), (unless it iscovered with a floor finish which is highly vapourresistant, in which case see alternative approach paragraph 3.11):

(a) ground covering either

i. concrete at least 100mm thick, composed of50kg of cement to not more than 0.13m3 of fineaggregate and 0.18m3 of coarse aggregate orBS 5328 mix ST 1 if there is no embeddedsteel. The concrete should be laid on a hardcore bed of clean broken brick or any otherinert material free from materials includingwater-soluble sulphated in quantities whichcould damage the concrete, or

ii. concrete composed as described above or inert

fine aggregate, in either case at least 50mmthick laid on at least 300m (1200 gauge);

250m (1000 gauge) polythene in accordance

with appropriate BBA certificate or to the PIFAstandard is also satisfactory.

To prevent water collecting on the ground covering,either the top should be entirely above the highestlevel of the adjoining ground or the covering shouldbe laid to fall to a drainage outlet above the lowestlevel of the adjoining ground (see Diagram 9).

b. ventilated air space measuring at least 75mmfrom the ground covering to the underside of anywall plates and at least 150mm to the underside ofthe suspended timber floor (or insulation if provided).

Two opposing external walls should have ventilationopenings placed so that the ventilating air will have afree path between opposite sides and to all parts.

The openings should be large enough to give anactual opening of at least equivalent to 1500mm2 foreach metre run of wall. Any pipes needed to carryventilating air should have a diameter of at least100mm.

c. damp-proof courses of impervious sheetmaterial, engineering brick or slates in cementmortar of other material which will prevent thepassage of moisture.

Alternative approach3.11 The performance (see paragraph 0.3 above)

can also be met by following the relevant recommen-dations of Clause 11 of CP 102: 1973 Protection ofbuildings against water from the ground.

Diagram 7 Suspended timber floor principle


15/22

Suspended concrete ground floors

3.12 Any suspended floor in in-situ or precastconcrete next to the ground will meet theperformance if it will adequately resist moisturefrom reaching the upper surface and if thereinforcement is protected against moisture.

Technical solution3.13 A suspended concrete floor may be built asfollows (see diagram 10):

a. in-situ concrete at least 100mm thick (butthicker if the structural design requires) containing atleast 300kg of cement for each m3 of concrete, or

b. precast concrete construction with or withoutinfilling slabs, and

c. reinforcing steel protected by concrete cover ofat least 40mm if the concrete is in-situ and at leastthe thickness required for a moderate exposure if the

concrete is precast.

3.14 A suspended concrete floor should incorporate:

a. damp-proof membrane (to be provided if theground below the floor has been excavated belowthe lowest level of the surrounding ground and willnot be effectively drained) and

b. in those situations where there is a risk of anaccumulation of gas which might lead to anexplosion, a ventilated air space. This shouldmeasure at least 150mm clear from the ground tothe underside of the floor (or insulation if provided).

c. where the ventilation referred to in b. above isprovided two opposing external walls should haveventilation openings placed so that the ventilating airwill have a free path between opposite sides and toall parts. The openings should be large enough togive an actual opening of at least equivalent to1500mm2 for each metre run of wall.


14

Diagram 8 Suspended timber floor construction

Diagram 9 Suspended floor

preventing water collection

Diagram 10 Suspended concreteground floor


16/22


15

WALLS

4.1 This Section gives guidance for two situations:

a. internal and external walls exposed to moisture

from the ground (see paragraphs 4.3 to 4.6).

b. cavity externals walls exposed to moisture fromoutside (see paragraphs 4.7 to 4.9).

A wall includes piers, columns and parapets. It alsoincludes chimneys if they are attached to thebuilding. A wall does not include windows, doors orsimilar openings.

4.2 Walls should:

a. resist the passage of moisture from the groundto the inside of the building (see Diagram 11), and

b. not be damaged by moisture from the groundand not carry moisture from the ground to any partwhich would be damaged by it

and, if the wall is an external wall:

c. resist the penetration of rain and snow to theinside of the building, and

d. not be damaged by rain and snow and notcarry rain and snow to any part which would bedamaged by it.

Internal and External walls(moisture from the ground)

4.3 Any internal or external wall will meet theperformance if a damp-proof course is provided.

Technical solution4.4 An internal or external wall may be built asfollows (unless it is subject to ground waterpressure, in which case see alternative approach paragraph 4.5):

a. damp-proof course of bituminous material,engineering bricks or slates in cement and mortar orany other material that will prevent the passage ofmoisture. The damp-proof course should becontinuous and with any damp-proof membrane inthe floors, and

b. if the wall is an external wall the damp-proofcourse should be at least 150mm above the level ofthe adjoining ground (see Diagram 12) unless thedesign is such that a part of the building will protectthe wall, and

c. if the wall is an external cavity wall the cavityshould be taken down at least 150mm below thelevel of the lowest damp-proof course of a damp-proof tray should be provided so as to prevent rainand snow passing to the inner leaf (see Diagram 13).

Section 4

Diagram 11 Walls principle

Diagram 12 Damp proof courses

Diagram 13 Protecting inner leaf


17/22

Alternative approach

4.5 The performance can also be met by followingthe relevant recommendations of Clauses 4 & 5 ofBS 8215: 1991 Code of practice for design andinstallation of damp-proof courses in masonryconstruction. BS 8102: 1990 Code of practice forprotection of structures against water from thegroundincludes recommendations for walls subject

to ground water pressure including basement walls.

Additional provisions for external

walls (moisture from the outside)

4.6 As well as giving protection against moisturefrom the ground an external wall should giveprotection against rain and snow. This protection canbe given by a solid wall which has an impervious orweather-resisting cladding (see Section 5) or by acavity wall (see paragraphs 4.7 to 4.10).

Cavity external walls

4.7 Any external cavity wall will meet theperformance if the outer leaf is separated from theinner leaf by a drained air space or in any other waywhich will prevent rain and snow from being carriedto the inner leaf.

Technical solution4.8 A cavity external wall may be built as follows:

a. outer leaf masonry (bricks, blocks, stone or caststone), and

b. cavity at least 50mm wide. The cavity to bebridged only by wall ties or by damp-proof traysprovided to prevent moisture being carried to theinner leaf (see paragraph 4.10 for cavity insulation),and

c. inner leaf masonry or frame with lining.

Where a cavity is to be partially filled, the residualcavity should be not less than 50mm (nominal) wide(see Diagram 14).

Alternative approach4.9 The performance can also be met by followingthe relevant recommendations of BS 5628 Code ofpractice for use of masonry. Part 3: 1985 Materialsand components, design and workmanship. TheCode indicates factors affecting rain penetration ofcavity walls.

Cavity insulation4.10 An insulating material may be placed in thecavity between the outer leaf and an inner leaf ofmasonry construction under the following conditions:

a. a rigid thermal insulating material built into thewall should be the subject of a current British Boardof Agrment Certificate or a European Technical

Approval and the work should be carried out inaccordance with the requirements of that document,and

b. urea-formaldehyde foam inserted into the cavityafter the wall has been constructed should be inaccordance with BS 5617: 1985 Specification forurea-formaldehyde (UF) foam systems suitable forthermal insulation of cavity walls with masonry orconcrete inner and outer leavesand should beinstalled in accordance with BS 5618: 1985 Code ofpractice for thermal insulation of cavity walls (withmasonry or concrete inner and outer leaves by filling

with urea-formaldehyde (UF) foam systems. Thesuitability of the wall for foam filling is to beassessed before the work is carried out and theperson undertaking the work should hold or operateunder a current BSI Certificate of Registration ofAssessed Capability or a similar document issued byan equivalent body.

c. other insulating materials inserted into thecavity after the wall has been constructed should beinstalled in accordance with BS 6232 Thermalinsulation of cavity walls by filling with blownman-made mineral fibrePart 1: 1982 Specification

for the performance of installation systems and Part2: 1982 Code of practice for installation of blownman-made mineral fibre in cavity walls with masonryand/or concrete leaves. The suitability of the wall forfilling is to be assessed before the work is carriedout and the person undertaking the work should holdor operate under a current BSI Certificate ofRegistration of Assessed Capability or a similardocuments issued by an equivalent body.

Alternatively the insulating material should be thesubject of a current British Board of AgrmentCertificate or a European Technical Approval. The

work should be carried out in accordance with theterms of that document by operative either directlyemployed by the holder of the document oremployed by an installer approved to operate underthe document.


16


18/22


17

4.11 The suitability of the wall for filling should beassessed before the work is carried out inaccordance with BS 8208 Guide to assessment ofsuitability of external cavity walls for filling withthermal insulants, Part 1: 1985 existing traditionalcavity construction.

Diagram 14 Insulated external walls:examples


19/22

CLADDING FOR EXTERNALWALLS AND ROOFS

5.1 Cladding should:

a. resist the penetration of rain and snow to theinside of the building, and

b. not be damaged by rain or snow and not carryrain or snow to any part of the building which wouldbe damaged by it. (see Diagram 17).

5.2 Cladding can be designed to protect a buildingfrom rain or snow (often driven by the wind) either byholding it at the face of the building or by stopping it

from penetrating beyond the back of the cladding.(see Diagram 16).

5.3 Any cladding will meet the performance if:

a. it is jointless or has sealed joints, and isimpervious to moisture (so that moisture will notenter the cladding), or

b. it has overlapping dry joints, is impervious orweather-resisting, and is backed by a material whichwill direct rain or snow which enters the claddingtowards the outside face.

5.4 Some materials can deteriorate rapidly withoutspecial care and they should only be used as theweather-resisting part of a wall or roof if certainconditions are met (see Technical GuidanceDocument supporting Bye-Law 7, Materials andWorkmanship).

The weather-resisting part of a wall or roof does notinclude paint nor does it include any coatingsurfacing or rendering which will not itself provideall the weather resistance.

Technical solution5.5 Cladding may be:

a. impervious including metal, plastic, glass andbituminous products, or

b. weather-resisting including natural stone orslate, cement based products, fired clay and wood,or

c. moisture-resisting including bituminous andplastic products lapped at the joints, if used as asheet material, and permeable to water vapourunless there is a ventilated space directly behind thematerial, or

d. jointless materials and sealed joints, whichshould allow for structural and thermal movement.

5.6 Dry joints between cladding units should bedesigned so that rain and snow will not pass throughthem, or the cladding should be designed so thatrain or snow which enters the joints will be directedtowards the exposed face without it penetratingbeyond the back of the cladding.

Note: Whether dry joints are suitable will dependon the design of the joint or the design of thecladding and the severity of the exposure towind and rain.


18

Section 5

Diagram 15 Cladding principle

Diagram 16 Cladding ofwalls and roofs


20/22

5.7 Each sheet, tile and section of cladding shouldbe securely fixed.

5.8 Insulation can be incorporated into theconstruction provided it is either protected frommoisture or is unaffected by it. Problems can arise insuch constructions from condensation and from coldbridges; guidance is given in the Technical Guidance

Document supporting part 5, Ventilation and in theBRE publication Thermal Insulation: avoiding risks.

Alternative approach5.9 The performance can also be met by followingthe relevant recommendations of:

a. (for walls and roofs) BS CP 143: Code ofpractice for sheet roof and wall coverings. The Codeincludes recommendations for:corrugated and troughed aluminium (Part 1: 1958),

zinc (Part 5: 1964),galvanized corrugated steel (Part 10: 1973),copper (Part 12: 1970 (1988))aluminium (Part 15: 1973 (1986))semi-rigid asbestos bitumen sheets (Part 16: 1974).Recommendations for lead are included in BS 6915:1988 Specification for design and construction offully supported lead sheet roof and wall covering.

b. (for walls and roof) BS 5247: Code of practicefor sheet wall and floor coveringsPart 14: 1975Corrugated asbestos-cement, and

c. (for walls and steep roofs) BS8200: 1985 Code

of practice for the design of non load-bearingexternal vertical enclosures of buildings, and

d. (for walls only) BS CP 297: 1972 Precastconcrete cladding (non-loadbearing), and

e. (for walls only) BS 8298: 1989 Code of practicefor design and installation of natural stone claddingand lining.

These documents describe the materials and containdesign considerations including recommendationsfor fixing.


19


21/22

BS 5930: 1981 Code of practice for siteinvestigation.

DD 175: 1988 Code of practice for the identificationof potentially contaminated land and its investigation.

BS 1282: 1975 Guide to the choice, use andapplication of wood preservatives.

BS 5247 Code of practice for sheet roof and wallcoverings:Part 14: 1975 Corrugated asbestos-cementAmendment slips1: AMD 2821,2: AMD 3502.

BS 5262: 1976 Code of practice, External renderedfinishes,Amendment slips

1:AMD 2102: AMD 6246

BS 5328: Concrete:Part 1: 1990 Guide to specifying concrete

Part 2: 1990 Method for specifying concrete mixes.

BS 5390: 1976 (1984) Code of practice for stonemasonryAmendment slip1: AMD 4272.

BS 5617: 1985 Specification for urea-formaldehyde(UF) foam systems suitable for thermal insulation of

cavity walls with masonry or concrete inner andouter leaves.

BS 5618: 1985 Code of practice for thermalinsulation of cavity walls (with masonry or concreteinner and outer leaves) by filling with urea-formaidehyde (UF) foam systems.Amendment slip1: AMD 6262.

BS 5628: Code of practice for use of masonry:Part 3: 1985 Materials and components, design andworkmanship.

BS 6232: Thermal insulation of cavity walls by fillingwith blown man-made mineral fibre:Part 1: 1982 Specification for the performance ofinstallation systems.Amendment slip1: AMD 5428Part 2: 1982 Code of practice for installation ofblown man-made mineral fibre in cavity walls withmasonry and/or concrete leaves.

BS 6915: 1988 Specification for design andconstruction of fully supported lead sheet roof andwall coverings.

BS 8200: 1985 Code of practice for design ofnon-loadbearing external vertical enclosures ofbuildings.

BS 8102: 1990 Code of practice for protection ofstructures against water from the ground.

BS 8208: Guide to assessment of suitability ofexternal cavity walls for filling with thermal insulants:Part 1: 1985 Existing traditional cavity construction.

BS 8215: 1991 Code of practice for design andinstallation of damp-proof courses in masonryconstruction.

BS 8298: Code of practice for design and installationof natural stone cladding and lining.

CP 102: 1973 Code of practice for protection ofbuildings against water from the ground,Amendment slips1: AMD 1151,2: AMD 2196,

3: AMD 2470.CP 143 Code of practice for sheet roof and wallcoverings:Part 1: 1958 Aluminium, corrugated and troughed

Part 5: 1954 Zinc

Part 10: 1973 Galvanised corrugated steelPart 12: 1970 CopperAmendment slips1: AMD 863,2: AMD 5193.Part 15: 1973 (1986) AluminiumAmendment slip

1: AMD 4473,Part 16: 1974 Semi-rigid asbestos bitumen sheet.

CP 297: 1972 Precast concrete cladding (non-loadbearing).

DD 93: 1984 Methods for assessing exposure towind-driven rain.


20

Standards referred to


22/22

List of codes of practice currently issued or approvedby the Planning and Environment Committee for thepurpose of showing compliance with the BuildingBye-Laws (Jersey) 1997.

Technical Guidance Document. Part 1 StructureTechnical Guidance Document. Part 2 Fire Safety

Technical Guidance Document. Part 3 Heat Producing Appliances and Storage of FuelsTechnical Guidance Document. Part 4 Site Preparation and Resistance to MoistureTechnical Guidance Document. Part 5 VentilationTechnical Guidance Document. Part 6 Drainage, Hygiene and Water StorageTechnical Guidance Document. Part 7 Stairs, Ramps and Protective BarriersTechnical Guidance Document. Part 8 Access and Facilities for disabled PeopleTechnical Guidance Document. Part 9 Resistance to the Transmission of SoundTechnical Guidance Document. Part 10 GlazingSafety and ProtectionTechnical Guidance Document. Part 11 Conservation of Fuel and PowerTechnical Guidance Document. Supporting Bye-Law 7. Materials and Workmanship

Date post:	03-Jun-2018
Category:	Documents
Upload:	asafridis
View:	214 times
Download:	0 times