A - Structure Building Regs

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Approved Document A Structure

Contents

PAGE

Use of guidance 3

Loading and Ground MovementThe Requirements A1/2 5

Guidance 6

Introduction 6

Section 1: Codes, standards andreferences for all building types 7

Introduction 7

References 7

Loading 7

Structural work of timber 7

Structural work of masonry 7

Structural work of reinforced,pre-stressed or plain concrete 7

Structural work of steel 7

Structural work of aluminium 7

Foundations 7

Ground movement (Requirement A2b) 8

Existing buildings 8

Section 2: Sizes of structural elementsfor certain residential buildings and other

small buildings of traditional construction 9General 9

Definitions 9

Section 2A: Basic requirements for stability 10

Section 2B: Sizes of certain timbermembers in floors and roofs for dwellings.Areas at risk from house longhorn beetle 11

Sizing of members 11

House longhorn beetle 11

Section 2C: Thickness of walls in certainsmall buildings 12

Application 12

Wall types 12

The use of this section 12

Conditions relating to the building ofwhich the wall forms part 12

Thickness of walls 13

Conditions relating to the wall 16

PAGE

Construction materials and workmanship 17

Loading on walls 23

End restraint 23

Openings, recesses, overhangs and chases 25

Lateral support by roofs and floors 26

Interruption of lateral support 29

Small single-storey non-residential buildingsand annexes 29

Section 2D: Proportions for masonrychimneys above the roof structure 33

Height to width relationship 33

Section 2E: Foundations of plain concrete 34

Conditions relating to the ground 34

Design provisions 34

Minimum width of strip foundations 34

Minimum depth of strip foundations 35

Section 3: Wall cladding 36

General 36

Technical approach 36

Loading 36

Fixings 36Further guidance 37

Section 4: Roof covering 38

Materials 38

Re-covering of roofs 38

Disproportionate CollapseThe Requirement A3 39

Guidance 40

Performance 40

Introduction 40

Section 5: Reducing the sensitivity of thebuilding to disproportionate collapse inthe event of an accident 41

Alternative approach 42

Standards referred to 44

A
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Structure Approved Document A

PAGE

DIAGRAMS

1. Size and proportion of residentialbuildings of not more than three storeys 13

2. Size and proportion of non-residentialbuildings and annexes 14

3. Determination of wall thickness 15

4. Parapet walls: height 16

5. Maximum floor area enclosed bystructural walls 17

6. Map showing wind speed in m/s formaximum height of buildings 18

7. Maximum height of buildings 19

8. Measuring storey and wall heights 20

9. Declared compressive strength ofmasonry units 22

10. Maximum span of floors 23

11. Differences in ground levels 24

12. Openings in a buttressing wall 25

13. Buttressing 26

14. Sizes of openings and recesses 27

15. Lateral support by floors 28

16. Lateral support at roof level 29

17. Size and location of openings 30

18. Wall thickness 31

19. Lateral restraint at roof level 32

20. Proportions for masonry chimneys 33

21. Elevation of stepped foundation 34

22. Piers and chimneys 34

23. Foundation dimensions 34

24. Area at risk of collapse in the event ofan accident 43

PAGE

TABLES

1. Areas at risk from houselonghorn beetle 11

2. Wall types considered in this section 12

3. Minimum thickness of certainexternal walls, compartment wallsand separating walls 15

4. Imposed loads 17

5. Cavity wall ties 21

6. Declared compressive strength ofmasonry units complying withBS EN 771-1 to -5 21

7. Normalised compressive strength ofmasonry units of clay and calciumsilicate blocks complying withBS EN 771-1 and -2 23

8. Value of Factor X 27

9. Lateral support for walls 27

10. Minimum width of strip footings 35

11. Building classes 41

A CONTENTS


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THE APPROVED DOCUMENTS

This document is one of a series that has beenapproved by the First Secretary of State for thepurpose of providing practical guidance withrespect to the requirements of Schedule 1 to and

Regulation 7 of the Building Regulations 2000 (SI2000/2531) for England and Wales. SI 2000/2531has been amended by the Building (Amendment)Regulations 2001 (SI 2001/3335), by the Building(Amendment) Regulations 2002 (SI 2002/440), bythe Building (Amendment) (No. 2) Regulations2002 (SI 2001/2871), by the Building (Amendment)Regulations 2003 (SI 2003/2692) and by the Building(Amendment) Regulations 2004 (SI 2004/1465).

At the back of this document is a list of all thedocuments that have been approved and issuedby the Secretary of State for this purpose.

Approved Documents are intended to provideguidance for some of the more commonbuilding situations. However, there may well bealternative ways of achieving compliance withthe requirements. Thus there is no obligation toadopt any particular solution contained in anApproved Document if you prefer to meet therelevant requirement in some other way.

Other requirements

The guidance contained in an ApprovedDocument relates only to the particularrequirements of the Regulations which that

document addresses. The building work willalso have to comply with the requirements ofany other relevant paragraphs in Schedule 1to the Regulations.

There are Approved Documents which giveguidance on each of the parts of Schedule 1and on Regulation 7.

LIMITATION ON REQUIREMENTS

In accordance with regulation 8, the requirementsin Parts A to K and N of Schedule 1 to theBuilding Regulations do not require anything

to be done except for the purpose of securingreasonable standards of health and safety forpersons in or about the buildings.

MATERIALS AND WORKMANSHIP

Any building work which is subject torequirements imposed by Schedule 1 to theBuilding Regulations should, in accordancewith Regulation 7, be carried out with propermaterials and in a workmanlike manner.

You may show that you have complied withregulation 7 in a number of ways. These include

the appropriate use of a product bearing CEmarking in accordance with the ConstructionProducts Directive (89/106/EEC)1 as amendedby the CE Marking Directive (93/68/EEC)2, or a

product complying with an appropriate technicalspecification (as defined in those Directives),a British Standard, or an alternative nationaltechnical specification of any state which is acontracting party to the European Economic Areawhich, in use, is equivalent, or a product coveredby a national or European certificate issued bya European Technical Approval Issuing body,and the conditions of use are in accordance withthe terms of the certificate. You will find furtherguidance in the Approved Document supportingRegulation 7 on materials and workmanship.

Independent certification schemes

There are many UK product certificationschemes. Such schemes certify compliancewith the requirements of a recognised documentwhich is appropriate to the purpose for which thematerial is to be used. Materials which are not socertified may still conform to a relevant standard.

Many certification bodies which approve suchschemes are accredited by UKAS.

Technical specifications

Building Regulations are made for specificpurposes: health and safety, energy conservationand the welfare and convenience of disabledpeople. Standards and technical approvals arerelevant guidance to the extent that they relateto these considerations. However, they may alsoaddress other aspects of performance such as

serviceability, or aspects which although theyrelate to health and safety are not covered bythe Regulations.

When an Approved Document makes referenceto a named standard, the relevant version ofthe standard is the one listed at the end of thepublication. However, if this version has beenrevised or updated by the issuing standardsbody, the new version may be used as a sourceof guidance provided it continues to address therelevant requirements of the Regulations.

The appropriate use of a product which complies

with a European Technical Approval as defined inthe Construction Products Directive will meet therelevant requirements.

The Department intends to issue periodicamendments to its Approved Documents toreflect emerging harmonised European Standards.Where a national standard is to be replaced by aEuropean harmonised Standard, there will be aco-existence period during which either standardmay be referred to. At the end of the co-existenceperiod the national standard will be withdrawn.

Use of guidance A

1 As implemented by the Construction Products Regulations 1991

(SI 1991/1620).

2 As implemented by the Construction Products (Amendment) Regulations

1994 (SI 1994/3051).


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THE WORKPLACE (HEALTH,

SAFETY AND WELFARE)

REGULATIONS 1992

The Workplace (Health, Safety and Welfare)Regulations 1992 contain some requirementswhich affect building design. The main

requirements are now covered by the BuildingRegulations, but for further information see:Workplace health, safety and welfare, TheWorkplace (Health, Safety and Welfare)Regulations 1992, Approved Code of Practiceand Guidance;The Health and SafetyCommission, L24; Published by HMSO 1992;ISBN 0 11886 333 9.

The Workplace (Health, Safety and Welfare)Regulations 1992 apply to the common partsof flats and similar buildings if people such ascleaners and caretakers are employed to workin these common parts. Where the requirements

of the Building Regulations that are covered bythis Part do not apply to dwellings, the provisionsmay still be required in the situations describedabove in order to satisfy the Workplace Regulations.

OTHER FORMS OF HOUSE

CONSTRUCTION

This Approved Document includes guidance onstructural elements of residential buildings oftraditional masonry construction. It is recognised,however, that there are other suitable forms ofconstruction in use in the housing sector some of

which (e.g. timber framed) have been in commonuse for a number of years and have demonstratedan adequate performance in compliance with theA1 requirement. Such alternative forms includeprefabricated timber, light steel and precastconcrete framed construction.

A number of guidance documents relating tothese alternative forms are presently beingdeveloped by industry. The intention is toreference these in this Approved Documentas soon as they become available and areapproved by the Secretary of State.

EUROCODESThe British Standards Institution will shortlybe publishing a series of Structural Eurocodes,together with their National Annexes. TheseEurocodes are CEN Standards comprising manyParts which, when used in conjunction with theirNational Annexes and when approved by theSecretary of State, are intended to be referencedin this Approved Document as practical guidanceon meeting the Part A Requirements.

A USE OF GUIDANCE


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The Requirements

This Approved Document deals with the followingRequirements which are contained in the BuildingRegulations 2000 (as amended by SI 2001/3335,SI 2002/440, SI 2002/2871 and SI 2003/2692).

Requirement Limits on application

Loading

A1. (1) The building shall be constructed so that the combined dead,

imposed and wind loads are sustained and transmitted by it to the

ground:

(a) safely; and

(b) without causing such deflection or deformation of any

part of the building, or such movement of the ground, as will impair

the stability of any part of another building.

(2) In assessing whether a building complies with sub paragraph

(1) regard shall be had to the imposed and wind loads to which it is

likely to be subjected in the ordinary course of its use for the purpose

for which it is intended.

Ground movement

A2. The building shall be constructed so that ground movement

caused by:

(a) swelling, shrinkage or freezing of the subsoil; or

(b) land-slip or subsidence (other than subsidence arising from

shrinkage, in so far as the risk can be reasonably foreseen), will not

impair the stability of any part of the building.

LOADING AND GROUND MOVEMENT A1/2


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Introduction

0.1 In the Secretary of States view therequirements of A1 and A2 will be met byfollowing the recommendations given in thedocuments listed in Section 1 or by adopting

the guidance in Sections 2-4:

a. Section 1is relevant to all building typesand lists Codes, Standards and otherreferences for structural design andconstruction but, where they do not giveprecise guidance, consideration shouldbe given to paragraph 0.2.

b. Section 2give sizes of structural elementsfor certain residential buildings and othersmall buildings of traditional construction.

c. Section 3gives guidance on the supportand fixing of wall cladding.

d. Section 4gives guidance where roofs areto be re-covered as a material alteration asdefined in the Regulations.

0.2 The safety of a structure depends on thesuccessful combination of design and completedconstruction, particularly:

a. The design should be based on identificationof the hazards to which the structure is likelyto be subjected and assessment of the risks.The selection of relevant critical situationsfor design should be made reflecting theconditions that can reasonably be foreseen

during future use.

b. Loading. Dead load, imposed load and windload should be in accordance with the currentCodes of Practice referred to in Section 1 ofthis document.

c. Properties of materials.

d. Detailed design and assembly ofthe structure.

e. Safety factors.

f. Workmanship.

The numeric values of safety factors, whetherexpressed explicitly or implicitly in designequations, or design values, should be derivedfrom considerations of the above aspects ofdesign and construction as a whole. A change inany one of these aspects may disturb the safetyof the structure.

Loads used in calculations should allow forpossible dynamic, concentrated and peak loadeffects that may occur.

0.3 Grandstands and structures erected inplaces of public assembly may need to sustain thesynchronous or rhythmic movement of numbers

of people. It is important to ensure that the designof the structure takes these factors into accountso as to avoid the structure being impaired orcausing alarm to people using the structure.

Interim guidance on the design of grandstandsmay be found in Dynamic performancerequirements for permanent grandstands subjectto crowd action, Interim Guidance on assessmentand design published by the Institution ofStructural Engineers, November 2001.

Supplementary advice on the dynamic testingof grandstands and seating decking has beenpublished in an Advisory Note by the Institutionof Structural Engineers, June 2002.

GuidanceA1/2


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Introduction

1.1 This section is relevant to all building typesand lists codes, standards and other referencesfor structural design and construction.

References

1.2 Loading:

a. Dead and imposed loads

BS 6399-1:1996 Loading for buildings. Code ofpractice for dead and imposed loads.

b. Wind loads

BS 6399-2:1997 Loading for buildings. Codeof practice for wind loads

BRE digest 436 Parts 1, 2 and 3 (Brief guidancefor using BS 6399-2:1996).

c. Imposed roof loads

BS 6399-3:1998 Loading for buildings. Code ofpractice for imposed roof loads.

1.3 Structural work of timber:

BS 5268-2:2002 Structural use of timber. Code ofpractice for permissible stress design, materialsand workmanship.

BS 5268-3:1998 Structural use of timber. Code ofpractice for trussed rafter roofs.

BS 8103-3:1996 Structural design of low-risebuildings. Code of practice for timber floors androofs for housing.

1.4 Structural work of masonry:

BS 5628-1:1992 Code of practice for use ofmasonry. Structural use of unreinforced masonry.

BS 5628-2:2000 Code of practice for use ofmasonry. Structural use of reinforced andpre-stressed masonry.

BS 5628-3:2001 Code of practice for use of

masonry. Materials and components, designand workmanship.

BS 8103-1:1995 Structural design of low-risebuildings. Code of practice for stability, siteinvestigation, foundations and ground floorslabs for housing.

BS 8103-2:1996 Structural design of low-risebuildings. Code of practice for masonry wallsfor housing.

1.5 Structural work of reinforced,pre-stressed or plain concrete:

BS 8110-1:1997 Structural use of concrete.Code of practice for design and construction.

BS 8110-2:1985 Structural use of concrete.Code of practice for special circumstances.

BS 8110-3:1985 Structural use of concrete.Design charts for singly reinforced beams, doublyreinforced beams and rectangular columns.

BS 8103-4:1995 Structural design of low-risebuildings. Code of practice for suspendedconcrete floors for housing.

1.6 Structural work of steel:

BS 5950-1:2000 Structural use of steelwork inbuilding. Code of practice for design in simpleand continuous construction: hot rolled andwelded sections.

BS 5950-2:2001 Structural use of steelwork inbuilding. Specification for materials, fabricationand erection, hot rolled sections.

BS 5950-3-1:1990 Structural use of steelwork inbuilding. Design in composite construction. Codeof practice for design of simple and continuouscomposite beams.

BS 5950-4:1994 Structural use of steelworkin building. Code of practice for design ofcomposite slabs with profiled steel sheeting.

BS 5950-5:1998 Code of practice for designof cold formed thin gauge sections.

BRE Digest 437 Industrial platform floors:mezzanine and raised storage.

1.7 Structural work of aluminium:BS 8118-1:1991 Structural use of aluminium.Code of practice for design.

BS 8118-2:1991 Structural use of aluminium.Specification for materials, workmanshipand protection.

1.8 Foundations:

BS 8002:1994 Code of practice for earthretaining structures.

BS 8004:1986 Code of practice for foundations.

Section 1: Codes, standards and referencesfor all building types

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Ground movement

(Requirement A2b)

1.9 There may be known or recordedconditions of ground instability, such as thatarising from landslides, disused mines orunstable strata which, if ignored, can have adevastating effect on the safety of a building

and its environs. Such conditions should betaken into account in the design of the buildingand its foundations. Attention is drawn to DOEPlanning Policy Guidance Note 14 Developmenton unstable land (obtainable from The StationeryOffice), which sets out the broad planning andtechnical issues relating to development onunstable land.

The Department has also sponsored a seriesof reviews aimed at determining the scale andnature of problems arising from mining instability,natural underground cavities and adversefoundation conditions. Databases of both

subsidence incidents and subsidence potentialproduced from these reviews are available fromthe following licence holders:

British Geological Survey, Sir Kingsley DunhamCentre, Keyworth, Nottingham NG12 5GG.

Landmark, 7 Abbey Court, Eagle Way, Exeter,Devon EX2 7HY.

Peter Brett Associates, 16 Westcote Road,Reading, Berkshire RG20 2DE.

Catalytic Data Ltd, The Spinney, 19 WoodlandsRoad, Bickley, Kent BRI 2AD.

The reports from these reviews, which include1:250,000 scale maps showing the distributionof the physical constraints, are available from thefollowing organisations:

Arup Geotechnics, 1991. Review of mininginstability in Great Britain.

Obtainable from Arup Geotechnics, Bede House,All Saints, Newcastle-upon-Tyne NE1 2EB.

Applied Geology Ltd, 1994. Review of instabilitydue to natural underground cavities in GreatBritain.

Obtainable from Kennedy & Donkin Ltd,14 Calthorpe Road, Edgbaston, BirminghamB15 1TH.

Wimpey Environmental Ltd, and National HouseBuilding Council, 1995. Foundation conditionsin Great Britain, a guide for planners anddevelopers. Obtainable from ESNR InternationalLtd, 16 Frogmore Road, Hemel Hempstead,Hertfordshire HP3 9RW.

Existing buildings

1.10 Compliance with Part A (Structure) isrequired in certain classes of change of use of abuilding, subject to the control of Regulations 5and 6. Guidance relevant to structural appraisalsrelated to change of use is given in the followingdocuments:

a. BRE Digest 366: Structural Appraisal ofExisting Buildings for Change of Use.

b. The Institution of Structural Engineers ReportAppraisal of Existing Structures, 1996.

Note: With reference to the item design checksin the above mentioned Institution of StructuralEngineers report the choice of various partialfactors should be made to suit the individualcircumstances of each case.

A1/2 CODES, STANDARDS AND REFERENCES FOR ALL BUILDING TYPES


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Section 2: Sizes of structural elements forcertain residential buildings and other smallbuildings of traditional construction

General

2.1 This section is presented as follows:

Section 2A

Basic requirements for stability.

Section 2B

Sizes of certain timber members in floors androofs for dwellings.

Areas at risk from house longhorn beetle.

Section 2C

Thickness of masonry walls in certain residentialbuildings of not more than three storeys, smallsingle-storey non-residential buildings and annexes.

Section 2D

Proportions for masonry chimneys.

Section 2E

Foundations of plain concrete.

2.2 Section 2A gives general rules which mustbe observed in following Sections 2B and 2C.Sections 2B to 2E may be used independentlyof each other.

Throughout this section the diagrams are onlyillustrative and do not show all the details ofconstruction.

Definitions

2.3 The following meanings apply to termsthroughout this section:

Buttressing wallA wall designed andconstructed to afford lateral support to anotherwall perpendicular to it, support being providedfrom the base to the top of the wall.

Cavity widthThe horizontal distance betweenthe two leaves of a cavity wall.

Compartment wallA wall constructed as acompartment wall to meet the requirements ofregulation B3(2).

Dead loadThe load due to the weight ofall walls, permanent partitions, floors, roofsand finishes including services, and all otherpermanent construction.

Imposed loadThe load assumed to be producedby the intended occupancy or use, includingthe weight of movable partitions, distributed,concentrated, impact, inertia and snow loads,but excluding wind loads.

PierA member which forms an integral part

of a wall, in the form of a thickened section atintervals along the wall, so as to afford lateralsupport to the wall to which it is bonded orsecurely tied.

Separating wallA wall or part of a wall which iscommon to adjoining buildings, and constructedto meet the requirements of regulation B3(2).

SpacingThe distance between the longitudinalcentres of any two adjacent timber members ofthe same type, measured in the plane of floor,ceiling or roof structure.

SpanThe distance measured along the centre

line of a member between the centres of any twoadjacent bearings or supports.

Supported wallA wall to which lateral support isafforded by a combination of buttressing walls,piers or chimneys acting in conjunction withfloor(s) or roof.

Wind loadThe load due to the effect of windpressure or suction.

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Section 2A: Basic requirements for stability

2A1 This section must be used in conjunctionwith sections 2B and 2C and its principles relateto all forms of low-rise residential buildings.

2A2 Adequate provision shall be made toensure that the building is stable under the likely

imposed and wind loading conditions. This willcommonly necessitate meeting the followingrequirements:

a. That the overall size and proportioningof the building are limited in accordancewith the specific guidance for each form ofconstruction.

b. That a suitable layout of walls (both internaland external) forming a robust 3 dimensionalbox structure in plan is constructed withrestriction on the maximum size of cellsmeasured in accordance with the specificguidance for each form of construction.

c. That the internal and external walls areadequately connected either by masonrybonding or by using mechanical connections.

d. That the intermediate floors and roof are ofsuch construction and interconnection withthe walls that they provide local supportto the walls and also act as horizontaldiaphragms capable of transferring the windforces to buttressing elements of the building.

Note: A traditional cut timber roof (i.e. usingrafters, purlins and ceiling joists) generally hassufficient built in resistance to instability andwind forces (e.g. from hipped ends, tiling battens,rigid sarking or the like). However, the needfor diagonal rafter bracing equivalent to thatrecommended in BS 5268-3:1998 or Annex H ofBS 8103-3:1996 for trussed rafter roofs shouldbe considered especially for single-hipped andnon-hipped roofs of greater than 40 pitch todetached houses.

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Sizing of members

2B1 Guidance on the sizing of certain membersin floors and roofs is given in Span tables forsolid timber members in floors, ceilings and roofs(excluding trussed rafter roofs) for dwellings,published by TRADA, available from ChilternHouse, Stocking Lane, Hughenden Valley, HighWycombe, Bucks HP14 4ND.

Alternative guidance is available in BS 5268-2:2002Code of practice for permissible stress design,materials and workmanship, BS 5268-3:1998,Code of practice for trussed rafter roofs andBS 8103-3:1996 Structural design of low-rise

buildings, Code of Practice for timber floors androofs for dwellings.

Table 1 Areas at risk from house longhorn beetle

Geographical area

In the Borough of Bracknell Forest the parishes of Sandhurst and Crowthorne.

The Borough of Elmbridge

In the District of Hart, the parishes of Hawley and Yateley

The District of Runnymede

The Borough of Spelthorne

The Borough of Surrey Heath

In the Borough of Rushmoor, the area of the former district of Farnborough

The Borough of Woking

House longhorn beetle

2B2 In the geographical areas specified inTable 1, softwood timber for roof constructionor fixed in the roof space, including ceiling joistswithin the void spaces of the roof, should beadequately treated to prevent infestation by thehouse longhorn beetle (Hylotrupes bajulusL.).

Guidance on suitable preservative treatmentsis given within the British Wood Preserving andDamp-Proofing Associations Manual (2000revision), available from 1 Gleneagles House,Vernongate, South Street, Derby DE1 1UP.

Section 2B: Sizes of certain timber membersin floors and roofs for dwellings. Areas atrisk from house longhorn beetle

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Section 2C: Thickness of walls in certainsmall buildings

Application

2C1 This section applies to the followingbuilding types:

a. residential buildings of not more thanthree storeys;

b. small single-storey non-residentialbuildings;

c. small buildings forming annexes toresidential buildings (including garagesand outbuildings).

Wall types

2C2 Only the types of wall given in Table 2,which must extend to the full storey height, and

parapet walls are considered in this section.

The use of this section

2C3 When using this section it should benoted that:

a. this section must be used in conjunctionwith Section 2A;

b. if wall thickness is to be determinedaccording to paragraphs 2C5to 2C13, allappropriate design conditions given in thissection must be satisfied;

c. walls should comply with the relevantrequirements of BS 5628: Part 3: 2001, exceptas regards the conditions given in paragraphs2C4and 2C14to 2C38;

d. in formulating the guidance of this section theworst combination of circumstances likely toarise was taken into account. If a requirementof this part is considered too onerous in aparticular case it may be appropriate toconsider a minor departure on the basisof judgement and experience, or to showadequacy by calculation in respect of theaspect of the wall which is subject to thedeparture rather than for the entire wall;

Table 2 Wall types considered in this section

Residential buildings of up to three storeys

External walls

Internal load-bearing walls

Compartment walls

Separating walls

Small single-storey non-residential buildings and annexes

External walls

Internal load-bearing walls

e. the guidance given is based upon thecompressive strengths of bricks and blocksbeing not less than indicated in Tables 6 and 7.

BS 5628-1:1992 gives design strengths for wallswhere the suitability for use of masonry units ofother compressive strengths is being considered.

Conditions relating to the building

of which the wall forms part

2C4 This Section applies only to buildingshaving proportions within the followingparameters (see Diagrams 1 and 2):

a. residential buildings of not more thanthree storeys:

i. the maximum height of the buildingmeasured from the lowest finished groundlevel adjoining the building to the highestpoint of any wall or roof should not begreater than 15m, subject to the limitsof paragraph 2C16;

ii. the height of the building H should notexceed twice the least width of thebuilding W1;

iii. the height of the wing H2 should notexceed twice the least width of the wingW2 where the projection P exceeds twicethe width W2;

b. small single-storey non-residential buildings:height H should not exceed 3m and W (beingthe greatest length or width of the building)should not exceed 9m (see Diagram 2),subject to the limits of paragraph 2C16;

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c. annexes:height H as variously indicated inDiagram 2 should not exceed 3m, subject tothe limits of paragraph 2C16.

Thickness of walls

2C5 General wall thickness may be determinedaccording to this section provided:

a. conditions relating to the building of whichthe wall forms part (see paragraphs 2C4,2C14to 2C16, 2C38); and

b. conditions relating to the wall (see paragraphs2C17to 2C37) are met. (See Diagram 3.)

2C6 Solid external walls, compartment wallsand separating walls in coursed brickwork orblockwork:Solid walls constructed of coursedbrickwork or blockwork should be at leastas thick as 1/16 of the storey height. Furtherrequirements are given in Table 3.

2C7 Solid external walls, compartmentwalls and separating walls in uncoursed stone,flints, etc.:The thickness of walls constructedin uncoursed stone, flints, clunches, bricks orother burnt or vitrified material should not beless than 1.33 times the thickness determined

by paragraph 2C6.2C8 Cavity walls in coursed brickwork orblockwork:All cavity walls should have leavesat least 90mm thick and cavities at least 50mm

wide. The wall ties should have a horizontalspacing of 900mm and a vertical spacing of450mm, which is equivalent to 2.5 ties per squaremetre. Wall ties should also be provided, spacednot more than 300mm apart vertically, within adistance of 225mm from the vertical edges of allopenings, movement joints and roof verges. Forselection of wall ties for use in a range of cavitywidths refer to Table 5. For specification of cavitywall ties refer to paragraph 2C19.

For external walls, compartment walls andseparating walls in cavity construction, thecombined thickness of the two leaves plus 10mm

should not be less than the thickness determinedby paragraph 2C6 and Table 3 for a solid wall ofthe same height and length.

2C9 Walls providing vertical support toother walls:Irrespective of the material usedin the construction, a wall should not be less inthickness than any part of the wall to which itgives vertical support.

2C10 Internal load-bearing walls in brickworkor blockwork(except compartment walls orseparating walls): All internal load-bearing wallsshould have a thickness not less than:

(specified thickness from Table 3) 5mm2

Continued on page 16

THICKNESS OF WALLS IN CERTAIN SMALL BUILDINGS A1/2

Diagram 1 Size and proportion of residential buildings of not more than three storeys

See para 2C4


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A1/2 THICKNESS OF WALLS IN CERTAIN SMALL BUILDINGS

Diagram 2 Size and proportion of non-residential buildings and annexes

See paras 2C4b and 2C4c


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Table 3 Minimum thickness of certain external walls, compartment walls andseparating walls

Height of wall Length of wall Minimum thickness of wall

Not exceeding 3.5m Not exceeding 12m 190mm for whole of its height

Exceeding 3.5m but not exceeding 9m Not exceeding 9m 190mm for whole of its height

Exceeding 9m 290mm from the base for the height ofbut not exceeding 12m one storey and 190mm for the rest of its height

Exceeding 9m but not exceeding 12m Not exceeding 9m 290mm from the base for the height ofone storey and 190mm for the rest of its height

Exceeding 9m 290mm from the base for the height ofbut not exceeding 12m two storeys and 190mm for the rest of its height


Diagram 3 Determination of wall thickness

See para 2C5


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except for a wall in the lowest storey of a threestorey building, carrying load from both upperstoreys, which should have a thickness asdetermined by the equation or 140mm whicheveris the greatest.

2C11 Parapet walls:The minimum thicknessand maximum height of parapet walls should beas given in Diagram 4.

2C12 Single leaves of certain external walls:The single leaf of external walls of small single-storey non-residential buildings and of annexesneed be only 90mm thick, notwithstandingparagraphs 2C38.

2C13 Modular bricks and blocks:Wherewalls are constructed of bricks or blocks havingmodular dimensions derived from BS 6649:1985,wall thicknesses prescribed in this section whichderive from a dimension of brick or block maybe reduced by an amount not exceeding thedeviation from work size permitted by a British

Standard relating to equivalent sized bricks orblocks made of the same material.

2C14 Maximum floor area:The guidance ofthis section assumes that no floor enclosed bystructural walls on all sides exceeds 70m2, andthat no floor without a structural wall on one sideexceeds 36m2. (See Diagram 5.)

2C15 Imposed loads on roofs, floors andceilings:The design considerations given inthis section are intended to be adequate for the

imposed loads given in Table 4.

2C16 Maximum height of buildings:The design guidance in this section is basedon BS 6399-2:1997. The maximum heights ofbuildings given in Table c of Diagram 7 correlateto various site exposure conditions and windspeeds. A map showing wind speeds is givenin Figure 1 of Diagram 6.

Conditions relating to the wall

2C17 Maximum allowable length and heightof the wall:This section does not deal with walls

longer than 12m, measured from centre to centreof buttressing walls, piers or chimneys providingrestraint, or with walls exceeding 12m in height(see also Table 3).


Diagram 4 Parapet walls: height

See para 2C11


18/4617


Table 4 Imposed loadsElement Loading

Distributed loadsRoof 1.00kN/m for spans not exceeding 12m

1.5kN/m for spans not exceeding 6m

Floors Distributed load: 2.00kN/m

Ceilings Distributed load: 0.25kN/mtogether with concentrated load: 0.9kN

2C18 Rules of measurement for heights ofwalls and storeys:The height of a wall or a

storey should be measured in accordance withthe rules in Diagram 8.

Construction materials and

workmanship

2C19 Wall ties:Wall ties should either complywith BS 1243, DD 140, or BS EN 845-1 andshould be material references 1 or 3 in BS EN845 Table A 1 austenitic stainless steel. Wall tiesshould be selected in accordance with Table 5 ofthis Approved Document.

2C20 Masonry units:Walls should be properlybonded and solidly put together with mortar andconstructed of masonry units conforming to:

a. clay bricks or blocks to BS 3921:1985 orBS 6649:1985 or BS EN 771-1;

b. calcium silicate bricks to BS 187:1978 orBS 6649:1985 or BS EN 771-2;

c. concrete bricks or blocks to BS 6073-1:1981or BS EN 771-3 or -4;

d. square dressed natural stone to the appropriaterequirements described in BS EN 771-6 orBS 5628-3:2001;

e. manufactured stone to BS 6457:1984 orBS EN 771-5.

2C21 Compressive strength of masonry units:Minimum compressive strength requirementsfor masonry units according to BS EN Standardsare given in Diagram 9, where the masonry unitsindicated for Conditions A, B and C shouldhave declared compressive strengths of notless than the values given in Table 6. Normalisedcompressive strengths for block sized clay andcalcium silicate masonry units not complying withbrick dimensional format are given in Table 7.



Diagram 5 Maximum floor area enclosed by structural walls

See para 2C14


19/4618



Diagram 6 Map showing wind speeds in m/s for maximum height of buildings

See para 2C16


20/4619



Diagram 7 Maximum height of buildings

See para 2C16


21/4620



Diagram 8 Measuring storey and wall heights

See para 2C18


22/4621



Table 5 Cavity wall ties

Nominal cavitywidth mm(Note 1)

50 to 75

76 to 90

91 to 100

101 to 125

126 to 150

151 to 175

176 to 300

Tie length mm(Note 2)

200

225

225

250

275

300

(See Note 2)

Permissible type of tie

Tie shape in accordancewith BS 1243*

Butterfly, double triangle or vertical twist

Double triangle or vertical twist

Double triangle (Note 3) or vertical twist

Vertical twist

Vertical twist

Vertical twist

Vertical twist style

BS EN 845-1 tie(Note 4)

Types 1, 2, 3 or 4 to DD 140-2* andselected on the basis of the design

loading and design cavity width.

*Although BS 1243 and DD 140-2 were due to bewithdrawn on 1 February 2005, the tie user classes(types) given in Tables 1 and 3 of the latterdocument can continue to be used after this date.

Notes:

1. Where face insulated blocks are used the cavity width should be measured from the face of the masonry unit.

2. The embedment depth of the tie should not be less than 50mm in both leaves. For cavities wider than 180mm calculate the length as the structuralcavity width plus 125mm and select the nearest stock length.

3. Double triangle ties of this shape having a strength to satisfy Type 2 of DD 140-2* are manufactured. Specialist tie manufacturers should beconsulted if 225mm long double triangle format ties are needed for 91 to 100mm cavities.

4. Where BS EN 845-1 ties are used reference needs to be made additionally to DD 140-2* for the selection of the type (i.e. type 1, 2, 3 or 4) relevantto the performance levels given in DD 140-2.

Table 6 Declared compressive strength of masonry units complying withBS EN 771-1 to -5 (N/mm2)

Masonry unit Clay masonry units to Calcium silicate masonry Aggregate Autoclaved Manufactured BS EN 771-1 units to BS EN 771-2 concrete aerated conc. stone masonry masonry masonry units to units to units to BS EN 771-3 BS EN 771-4 BS EN 771-5

Condition A (See Diagram 9)Brick Group 1 Group 2 Group 1 Group 2 6.0

6.0 9.0 6.0 9.0

Block See Table 7 See Table 7 See Table 7 See Table 7 2.9* 2.9

Condition B (See Diagram 9)

Brick Group 1 Group 2 Group 1 Group 2 9.0 9.0 13.0 9.0 13.0


Condition C (See Diagram 9)

Brick Group 1 Group 2 Group 1 Group 2 18.0 18.0 25.0 18.0 25.0


AnyunitcomplyingwithBSEN771-5

will

beacceptableforconditionsA,

BandC

* These values are dry strengths to BS EN 772-1

Notes:

1. This table applies to Group 1 and Group 2 units.

2. For the EN 771 series of standards for masonry units the values of declared compressive strengths (N/mm) given in Table 6 are mean values.

3. Brick: a masonry unit having work sizes not exceeding 337.5mm in length or 112.5mm in height.

4. Block: a masonry unit exceeding either of the limiting work sizes of a brick and with a minimum height of 190mm. For blocks with smaller heights,excluding cuts or make up units, the strength requirements are as for brick except for solid external walls where the blocks should have acompressive strength at least equal to that shown for block for an inner leaf of a cavity wall in the same position.

5. Group 1 masonry units have not more than 25% formed voids (20% for frogged bricks). Group 2 masonry units have formed voids greater than25%, but not more than 55%.


23/4622



Diagram 9 Declared compressive strength of masonry units

See para 2C21


24/4623



Table 7 Normalised compressive strength of masonry units of clay and calciumsilicate blocks complying with BS EN 771-1 and 2 (N/mm2)

Standard

Clay masonry units to BS EN 771-1Calcium silicate masonry units toBS EN 771-2

Condition (See Diagram 9)

A

B

C

Group 1 masonry units

5.0

7.5

15.0

Group 2 masonry units

8.0

11.0

21.0

Notes:

1. Values in this table are normalised compressive strengths (N/mm). Compressive strengths of masonry units should be derived according to EN 772-1.

2. The table applies to clay and calcium silicate block masonry units where the work size exceeds 337.5mm in length or 112.5mm in height.

3. Group 1 masonry units have not more than 25% formed voids (20% for frogged bricks). Group 2 masonry units have formed voids greater than25%, but not more than 55%.

2C22 Mortar:Mortar should be:

a.

i. Mortar designation (iii) according to

BS BS 5628-3:2001.ii. Strength class M4 according to

BS EN 998-2.

iii. 1:1:5 or 6 CEM 1, lime and fine aggregatemeasured by volume of dry materials, or

b. of equivalent or greater strength anddurability to the specification in a. above.

Loading on walls

2C23 Maximum span of floors:The maximumspan for any floor supported by a wall is 6mwhere the span is measured centre to centre of

bearing (see Diagram 10).

2C24 Other loading conditions:

a. Vertical loading on walls should be distributed.This may be assumed for concrete floorslabs, precast concrete floors, and timberfloors designed in accordance with section2B, and where the bearing length for lintels is150mm or greater. Where a lintel has a clearspan of 1200mm or less the bearing lengthmay be reduced to 100mm.

b. Differences in level of ground or other solidconstruction between one side of the wall

and the other should be less than 4 times thethickness of the wall as shown in Diagram 11.

c. The combined dead and imposed loadshould not exceed 70kN/m at base of wall(see Diagram 11).

d. Walls should not be subjected to lateral loadother than from wind, and that covered byparagraph 2C24(b).

End restraint

2C25 Vertical Lateral Restraint to Walls

The ends of every wall should be bonded or

otherwise securely tied throughout their fullheight to a buttressing wall, pier or chimney.Long walls may be provided with intermediatebuttressing walls, piers or chimneys dividingthe wall into distinct lengths within each storey;each distinct length is a supported wall forthe purposes of this section. The intermediatebuttressing walls, piers or chimneys shouldprovide lateral restraint to the full height of thesupported wall, but they may be staggered ateach storey.

2C26 Buttressing Walls

If the buttressing wall is not itself a supportedwall its thickness T2 should not be less than:


Diagram 10 Maximum span of floors

See para 2C23


25/4624



Diagram 11 Differences in ground levels

See para 2C24b


26/4625



a. half the thickness required by this section foran external or separating wall of similar heightand length less 5mm; or

b. 75mm if the wall forms part of a dwellinghouse and does not exceed 6m in total height

and 10m in length; andc. 90mm in other cases.

The length of the buttressing wall shouldbe at least 1/6 of the overall height of thesupported wall and be bonded or securely tiedto the supporting wall and at the other end to abuttressing wall, pier or chimney.

The size of any opening in the buttressing wallshould be restricted as shown in Diagram 12.

2C27 Design criteria for piers and chimneysproviding restraint:

a. piers should measure at least 3 times thethickness of the supported wall and chimneystwice the thickness, measured at right angles

to the wall. Piers should have a minimumwidth of 190mm (see Diagram 13);

b. the sectional area on plan of chimneys(excluding openings for fireplaces and flues)should be not less than the area required

for a pier in the same wall, and the overallthickness should not be less than twice therequired thickness of the supported wall(see Diagram 13).

Openings, recesses, overhangs

and chases

2C28 General:

The number, size and position of openings andrecesses should not impair the stability of a wallor the lateral restraint afforded by a buttressingwall to a supported wall. Construction over

openings and recesses should be adequatelysupported.

Diagram 12 Openings in a buttressing wall

See para 2C26


27/4626


2C29 Dimensional criteria for openings andrecesses:

The dimensional criteria are given in Diagram 14and Table 8.

No openings should be provided in walls belowground floor except for small holes for servicesand ventilation, etc. which should be limitedto a maximum area of 0.1m at not less than2m centres.

2C30 Chases:a. vertical chases should not be deeper than 1/3

of the wall thickness or, in cavity walls, 1/3 ofthe thickness of the leaf;

b. horizontal chases should not be deeper than1/6 of the thickness of the leaf of the wall;

c. chases should not be so positioned as toimpair the stability of the wall, particularlywhere hollow blocks are used.

2C31 Overhangs:

The amount of any projection should not impair

the stability of the wall.

Lateral support by roofs and floors

2C32 A wall in each storey of a building shouldextend to the full height of that storey, and havehorizontal lateral supports to restrict movementof the wall at right angles to its plane.

2C33 Floors and roofs should:

a. act to transfer lateral forces from walls tobuttressing walls, piers or chimneys; and

b. be secured to the supported wall byconnections specified in paragraphs 2C34and 2C35.

2C34 The requirements for lateral restraint ofwalls at roof and floor levels are given in Table 9and guidance on satisfying the requirements isgiven in paragraphs 2C35and 2C36.

2C35 Walls should be strapped to floors aboveground level, at intervals not exceeding 2mand as shown in Diagram 15 by tension strapsconforming to BS EN 845-1. For corrosionresistance purposes, the tension straps shouldbe material reference 14 or 16.1 or 16.2

(galvanised steel) or other more resistant


Diagram 13 Buttressing

See para 2C27


28/4627



Diagram 14 Sizes of openings and recesses

See para 2C29

Table 8 Value of Factor X (see Diagram 14)

Span of timber Span of concrete floor into wall floor into wall

Span of floor Minimum is parallel max max max maxNature of Maximum thickness of to wall 4.5m 6.0m 4.5m 6.0mroof span roof span (m) wall inner (mm)

Value of factor X

Roof spans Not 100 6 6 6 6 6parallel to wall applicable

90 6 6 6 6 5

Timber roof 9 100 6 6 5 4 3spans into wall

90 6 4 4 3 3

Table 9 Lateral support for walls

Wall type Wall length Lateral support required

Solid or cavity: external Any length Roof lateral support by every roof forming a junction with thecompartment separating supported wall

Greater than 3m Floor lateral support by every floor forming a junction with the supported wall

Internal load-bearing wall (not being Any length Roof or floor lateral support at the top of each storeya compartment or separating wall)


29/4628


specifications including material references 1 or3 (austenitic stainless steel). The declared tensilestrength of tension straps should not be lessthan 8kN.

Tension straps need not be provided:

a. in the longitudinal direction of joists in housesof not more than 2 storeys, if the joists areat not more than 1.2m centres and have atleast 90mm bearing on the supported wallsor 75mm bearing on a timber wall-plate ateach end, and

b. in the longitudinal direction of joists in housesof not more than 2 storeys, if the joists arecarried on the supported wall by joist hangersin accordance with BS EN 845-1 of the restrainttype described in BS 5628-1 and shown inDiagram 15(c), and are incorporated at notmore than 2m centres, and

c. when a concrete floor has at least 90mmbearing on the supported wall (see Diagram

15(d)), and

d. where floors are at or about the same levelon each side of a supported wall, andcontact between the floors and wall is eithercontinuous or at intervals not exceeding 2m.Where contact is intermittent, the points ofcontact should be in line or nearly in line onplan (see Diagram 15(e)).

2C36 Gable walls should be strapped to roofs as

shown in Diagram 16(a) and (b) by tension strapsas described in 2C35.

Vertical strapping at least 1m in length should beprovided at eaves level at intervals not exceeding2m as shown in Diagram 16(c) and (d). Verticalstrapping may be omitted if the roof:

a. has a pitch of 15 or more, and

b. is tiled or slated, and

c. is of a type known by local experience to beresistant to wind gusts, and

d. has main timber members spanning onto the

supported wall at not more than 1.2m centres.


Diagram 15 Lateral support by floors

See para 2C35


30/4629



Interruption of lateral support

2C37 Where an opening in a floor or roof for astairway or the like adjoins a supported wall andinterrupts the continuity of lateral support, thefollowing conditions should be satisfied for thepurposes of Section 2C:

a. the maximum permitted length of the opening

is to be 3m, measured parallel to the supportedwall, and

b. where a connection is provided by meansother than by anchor, this should be providedthroughout the length of each portion of thewall situated on each side of the opening, and

c. where a connection is provided by mild steelanchors, these should be spaced closer than2m on each side of the opening to providethe same number of anchors as if there wereno opening, and

d. there should be no other interruption of

lateral support.

Small single-storey non-residential

buildings and annexes

2C38 Size and proportion

i. General

The guidance given applies in the followingcircumstances:

a. The floor area of the building or annexe doesnot exceed 36m.

b. The walls are solidly constructed in brickworkor blockwork using materials which complywith paragraphs 2C19to2C22.

c. Where the floor area of the building or annexeexceeds 10m the walls have a mass of notless than 130kg/m.

Note: There is no surface mass limitationrecommended for floor areas of 10m or less.

d. Access to the roof is only for the purposes of

maintenance and repair.

e. The only lateral loads are wind loads.

Diagram 16 Lateral support at roof level

See para 2C36


31/4630


f. The maximum length or width of the buildingor annexe does not exceed 9m.

g. The height of the building or annexe does notexceed the lower value derived from Diagram 2.

h. The roof is braced at rafter level, horizontallyat eaves level and at the base of any gable by

roof decking, rigid sarking or diagonal timberbracing, as appropriate, in accordance withBS 5268-3.

i. Walls are tied to the roof structure verticallyand horizontally in accordance with paragraphs2C32to 2C36and with horizontal lateralrestraint at roof level in accordance withparagraph (iv) below.

j. The roof structure of an annexe is securedto the structure of the main building at both

rafter and eaves level.


Diagram 17 Size and location of openings

See para 2C38


32/4631



(ii) Size and location of openings

One or two major openings not more than 2.1min height are permitted in one wall of the buildingor annexe only. The width of a single opening or

the combined width of two openings should notexceed 5m.

The only other openings permitted in a buildingor annexe are for windows and a single leaf door.The size and location of these openings shouldbe in accordance with Diagram 17.

(iii) Wall thickness and recommendationsfor piers

The walls should have a minimum thickness of 90mm.

Diagram 18 Wall thickness

See para 2C38


33/4632


Walls which do not contain a major openingbut exceed 2.5m in length or height should bebonded or tied to piers for their full height at notmore than 3m centres as shown in Diagram 18a.

Walls which contain one or two major openingsshould in addition have piers as shown inDiagrams 18b and 18c. Where ties are usedto connect piers to walls they should be flat,20mm x 3mm in cross section, be in stainlesssteel in accordance with clause 2C19, be placedin pairs and be spaced at not more than 300mmcentre vertically.

(iv) Horizontal lateral restraint at roof level

Walls should be tied horizontally at no more than2m centres to the roof structure at eaves level,base of gables and along roof slopes as shown

in Diagram 19 with straps fixed in accordancewith paragraphs 2C35and 2C36. Wherestraps cannot pass through a wall they shouldbe adequately secured to the masonry usingsuitable fixings. Isolated columns should alsobe tied to the roof structure (see Diagram 19).


Diagram 19 Lateral restraint at roof level

See para 2C38


34/4633


A1/2

Section 2D: Proportions for masonrychimneys above the roof surface

Height to width relationship

2D1 Where a chimney is not adequatelysupported by ties or securely restrained in anyway, its height if measured from the highest pointof intersection with the roof surface, gutter, etc.should not exceed 4.5W, provided the density ofthe masonry is greater than 1500kg/m3, where:

Wis the least horizontal dimension of thechimney measured at the same point ofintersection, and

His measured to the top of any chimney pot orother flue terminal (see Diagram 20).

Diagram 20 Proportions for masonrychimneys

See para 2D1


35/4634


Conditions relating to the ground

2E1 There should not be:

a. non-engineered fill (as described in BREDigest 427) or wide variation in ground

conditions within the loaded area; norb. weaker or more compressible ground at

such a depth below the foundation as couldimpair the stability of the structure.

Design provisions

2E2 The following design provisions relate tofoundations:

a. the foundations should be situated centrallyunder the wall;

b. for foundations in chemically aggressivesoil conditions guidance in BS 8500-1 and

BRE Special Digest 1 should be followed.In non-aggressive soils, concrete shouldbe composed of Portland cement to BS EN197-1 and -2 and fine and coarse aggregateconforming to BS EN 12620 and the mixshould comply with one of the followingrecommendations:

i. in proportion of 50kg of Portland cementto not more than 200kg (0.1m3) of fineaggregate and 400kg (0.2m3) of coarseaggregate; or

ii. grade ST2 or grade GEN I concrete to

BS 8500-2;c. minimum thickness T of concrete foundation

should be 150mm or P, whichever is thegreater where P is derived using Table 10and Diagram 23. Trench fill foundations maybe used as an acceptable alternative to stripfoundations;

d. foundations stepped on elevation shouldoverlap by twice the height of the step, bythe thickness of the foundation, or 300mm,whichever is greater (see Diagram 21).

For trench fill foundations the overlap should

be twice the height of the step or 1m,whichever is greater;

e. steps in foundations should not be of greaterheight than the thickness of the foundation(see Diagram 21);

f. foundations for piers, buttresses and chimneysshould project as indicated in Diagram 22 andthe projection X should never be less than thevalue of P where there is no local thickeningof the wall.

Minimum width of strip

foundations2E3 The recommended minimum widths offoundations given in Table 10 may be used.

Section 2E: Foundations of plain concreteA1/2

Diagram 21 Elevation of steppedfoundation

See paras 2E2d and e

Diagram 22 Piers and chimneys

See para 2E2f

Diagram 23 Foundation dimensions

See para 2E2c


36/46


37/4636


General

3.1 Wall cladding presents a hazard if itbecomes detached from the building. Thissection provides guidance on the supportand fixing of wall cladding. An acceptable

level of safety can be achieved by differentmeans depending on the type and location ofthe cladding. The guidance given relates toall forms of cladding, including curtain wallingand glass facades. It is not intended to provideguidance concerning the weather resistanceof wall cladding which is included in ApprovedDocument C, Site preparation and resistance tomoisture, or guidance on resistance to spread offire which is included in Approved Document B,Fire safety, or guidance in relation to soundinsulation, which is included in ApprovedDocument E, Resistance to the passage

of sound.

Technical approach

3.2 The cladding will meet the safetyrequirement if:

a. the cladding is capable of safely sustainingand transmitting to the supporting structureof the building all dead, imposed and windloads, and

b. the cladding is securely fixed to andsupported by the structure of the building.This shall comprise both vertical support

and horizontal restraint, andc. provision is made, where necessary, to

accommodate differential movement of thecladding and the supporting structure of thebuilding, and

d. the cladding and its fixings (includingany support components) are of durablematerials; the design life of the fixings beingnot less than that of the cladding. Fixingsshall be corrosion resistant and of a materialtype appropriate for the local environment.

Loading

3.3 Wind loading on the cladding shouldbe derived from BS 6399-2:1997 with dueconsideration given to local increases in windsuction arising from funnelling of the windthrough gaps between buildings. Guidance onfunnelling effects is given in BRE Digest 436Wind loading on buildings Brief guidancefor using BS 6399-2:1997 available from BRE,Bucknalls Lane, Garston, Watford, Herts WD2 7JR.

3.4 Where the cladding is required to supportother fixtures, e.g. handrails, and fittings, e.g.antennae and signboards, account should be

taken of the loads and forces arising from suchfixtures and fittings.

3.5 Where the wall cladding is required tofunction as pedestrian guarding to stairs, ramps,vertical drops of 600mm or greater or as avehicle barrier, then account should be taken ofthe additional imposed loading, as stipulated inApproved Document K, Protection from falling,collision and impact.

3.6 Where the wall cladding is required tosafely withstand lateral pressures from crowds,an appropriate design loading is given in BS6399 Part 1 and the Guide to Safety at SportsGrounds (4th Edition, 1997).

Fixings

3.7 The selection of fixings for supportingcladding should be determined from aconsideration of the proven performance of thefixing and the risks associated with the particular

application. In this regard applications should bedesignated as being either non-redundant (wherethe failure of a single fixing could lead to thedetachment of the cladding) or redundant (wherefailure or excessive movement of one fixingresults in load sharing by adjacent fixings) andthe required reliability of the fixing determinedaccordingly.

Note: Attention is drawn to the availabilityof anchors with an ETA (European TechnicalApproval) gained in accordance with therequirements of ETAG 001 Guideline forEuropean Technical Approval Metal Anchors

for use in ConcreteParts 1-5, which cover bothredundant and non-redundant applications, andPart 6 which covers Anchors for multiple usein non-structural applications and which caneffectively be regarded as covering redundantuse. The UK definition of multiple use iscontained in an annexe to the ETAG Part 6 andis framed in such a way that all applications canbe validated as to whether or not they conform tothis category without calculation. All ETAG partsmay be downloaded in English from www.eota.be.

3.8 The strength of fixings should be derivedfrom tests using materials representative of the

material into which the fixing is to be anchored,taking account of any inherent weaknesses thatmay affect the strength of the fixing, e.g. cracksin concrete due to shrinkage and flexure, or voidsin masonry construction. The design loads willgenerally be available from the manufacturerstest data determined from a European TechnicalApproval (ETA) or an extant British Standard.

Note: ETAS are available which cover use eitherin both cracked and non-cracked concrete or innon-cracked concrete only. Those which coverboth cracked and non-cracked concrete allowhigher loads for use in non-cracked than in

cracked concrete. Guidance on how to determinewhether a particular concrete section may beregarded as cracked or non-cracked withoutreverting to stress calculations is contained

Section 3: Wall claddingA1/2


38/4637


WALL CLADDING A1/2

in Use of anchors with European TechnicalApprovals. UK Guidance Distinctionbetween cracked and non-cracked concrete.This is available on the BBA websitewww.bbacerts.co.uk click tab ETA.

Further guidance

3.9 The use of large panels of glass incladding of walls and roofs where the claddingis not divided into small areas by load-bearingframing requires special consideration. Guidanceis given in the following documents:

The Institution of Structural Engineers Report onStructural use of glass in buildings dated 1999,available from 11 Upper Belgrave Street, LondonSW1X 8BH.

Nickel sulfide in toughened glass published bythe Centre for Window Cladding and Technologydated 2000.

3.10 Further guidance on cladding is given inthe following documents:

The Institution of Structural Engineers Report onAspects of Cladding dated 1995.

The Institution of Structural Engineers Reporton Guide to the structural use of adhesivesdated 1999.

BS 8297:2000 Code of practice for the designand installation of non-load-bearing pre-castconcrete cladding.

BS 8298:1994 Code of practice for the design andinstallation of natural stone cladding and lining.

3.11 Additional guidance on fixings is given inthe following documents:

ETAG No. 001 1997 Guideline for EuropeanTechnical Approvals of Metal Anchors for use inConcrete, European Organisation for TechnicalApprovals (EOTA), Brussels. All EOTA parts maybe downloaded in English from www.eota.be.

English version published by the British Boardof Agreement, PO Box 195, Bucknalls Lane,Garston, Watford, Hertfordshire WD25 9BA.

Part 1 Anchors in general.

Part 2 Torque controlled anchors.Part 3 Undercut anchors.

Part 4 Deformation controlled anchors.

Part 5 Bonded anchors.

Part 6 Metal anchors for redundant use inconcrete for lightweight systems.

BS 5080-1:1993 Structural fixings in concreteand masonry. Method of test for tensile loading.

CIRIA Report RP 566 Cladding Fixings: Goodpractice guidance, available from 6 StoreysGate, London SWIP 3AU.

CIRIA Reports C579 and C589 Retention ofmasonry facades Best practice guide.

Guidance notes published by the ConstructionFixings Association, c/o Institute of SpringTechnology, Henry Street, Sheffield,South Yorks S3 7EQ.

Guidance Note: Procedure for Site TestingConstruction Fixings (1994).

Guidance Note: European Technical Approvals

for Construction Fixings (1998).Guidance Note: Anchor Selection (1995).

Guidance Note: Fixings and Fire (1998).

Guidance Note: Anchor Installation (1996).

Guidance Note: Bonded Anchors (1999).

Guidance Note: Heavy Duty ExpansionAnchors (1997).

Guidance Note: Fixings for Brickwork andBlockwork (1997).

Guidance Note: Undercut Anchors (1998).

Guidance Note: Fixings and Corrosion (2002).


39/4638


Materials

4.1 All materials used to cover roofs,including transparent or translucent materials,but excluding windows of glass in residentialbuildings with roof pitches of not less than

15, shall be capable of safely withstandingthe concentrated imposed loads upon roofsspecified in BS 6399: Part 3.

Re-covering of roofs

4.2 The re-covering of roofs is commonlyundertaken to extend the useful life of buildings.Roof structures may be required to carryunderdrawing or insulation provided at a timelater than their initial construction. This sectionprovides guidance on determining whether suchwork to a roof constitutes a material alterationunder the Building Regulations.

4.3 Where the work involves a significantchange in the applied loading the structuralintegrity of the roof structure and the supportingstructure should be checked to ensure thatupon completion of the work the building is notless compliant with Requirement A1 than theoriginal building.

4.4 A significant change in roof loading iswhen the loading upon the roof is increased bymore than 15%.

4.5 Where such checking of the existing roofstructure indicates that the construction is unable

to sustain any proposed increase in loading (e.g.due to overstressed members or unacceptabledeflection leading to ponding), appropriatestrengthening work or replacement of roofingmembers should be undertaken. This is classifiedas a material alteration.

4.6 In carrying out the checks mentioned inparagraph 4.3an increase of stress in a structuralmember arising from increased loading doesnot necessarily indicate that the roof structure isless compliant than the original roof provided anadequate factor of safety is maintained.

4.7 Where work will significantly decreasethe roof dead loading, the roof structure and itsanchorage to the supporting structure shouldbe checked to ensure that an adequate factorof safety is maintained against uplift of the roofunder imposed wind loading.

Section 4: Roof coveringA1/2


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DISPROPORTIONATE COLLAPSE A3

This Approved Document deals with the followingRequirements which are contained in the BuildingRegulations 2000 (as amended by SI 2001/3335,SI 2002/440, SI 2002/2871 and SI 2003/2692).

Requirement Limits on application

Disproportionate collapse

A3. The building shall be constructed so that in the event of an accident

the building will not suffer collapse to an extent disproportionate to

the cause.

The Requirement


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Performance

In the Secretary of States view the Requirementof A3 will be met by an appropriate choiceof measures to reduce the sensitivity of abuilding to disproportionate collapse should

an accident occur.

Introduction

0.1 The guidance in Section 5 deals with themeans of meeting this performance criterion.

GuidanceA3


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A3

Section 5: Reducing the sensitivity of thebuilding to disproportionate collapse in theevent of an accident

5.1 The requirement will be met by

adopting the following approach for ensuringthat the building is sufficiently robust tosustain a limited extent of damage or failure,depending on the class of the building,without collapse.

a. Determine the building class from Table 11.

b. For Class 1 buildings Provided thebuilding has been designed and constructedin accordance with the rules given in thisApproved Document, or other guidancereferenced under Section 1, for meetingcompliance with requirement A1 and A2 innormal use, no additional measures are likelyto be necessary.

Table 11 Building classes

Classes Building type and occupancy

1 Houses not exceeding 4 storeys

Agricultural buildings

Buildings into which people rarely go, provided no part of the building is closer to another building, or area where peopledo go, than a distance of 1.5 times the building height

2A 5 storey single occupancy houses

Hotels not exceeding 4 storeys

Flats, apartments and other residential buildings not exceeding 4 storeys

Offices not exceeding 4 storeys

Industrial buildings not exceeding 3 storeys

Retailing premises not exceeding 3 storeys of less than 2000m floor area in each storey

Single-storey educational buildings

All buildings not exceeding 2 storeys to which members of the public are admitted and which contain floor areas notexceeding 2000m at each storey

2B Hotels, flats, apartments and other residential buildings greater than 4 storeys but not exceeding 15 storeys

Educational buildings greater than 1 storey but not exceeding 15 storeys

Retailing premises greater than 3 storeys but not exceeding 15 storeys

Hospitals not exceeding 3 storeys

Offices greater than 4 storeys but not exceeding 15 storeys

All buildings to which members of the public are admitted which contain floor areas exceeding 2000m but less than5000m at each storey

Car parking not exceeding 6 storeys

3 All buildings defined above as Class 2A and 2B that exceed the limits on area and/or number of storeys

Grandstands accommodating more than 5000 spectators

Buildings containing hazardous substances and/or processes

Notes:

1. For buildings intended for more than one type of use the Class should be that pertaining to the most onerous type.

2. In determining the number of storeys in a building, basement storeys may be excluded provided such basement storeys fulfil the robustnessrequirements of Class 2B buildings.

c. For Class 2A buildings Provide effective

horizontal ties, or effective anchorage ofsuspended floors to walls, as describedin the Codes and Standards listed underparagraph 5.2for framed and load-bearingwall construction (the latter being defined inparagraph 5.3below).

d. For Class 2B buildings Provide effectivehorizontal ties, as described in the Codes andStandards listed under paragraph 5.2for framedand load-bearing wall construction (the latterbeing defined in paragraph 5.3below), togetherwith effective vertical ties, as defined in theCodes and Standards listed under paragraph

5.2, in all supporting columns and walls.


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Alternatively, check that upon the notionalremoval of each supporting column and eachbeam supporting one or more columns, or anynominal length of load-bearing wall (one at atime in each storey of the building), the buildingremains stable and that the area of floor at anystorey at risk of collapse does not exceed 15%of the floor area of that storey or 70m2, whichever

is smaller, and does not extend further than theimmediate adjacent storeys (see Diagram 24).

Where the notional removal of such columnsand lengths of walls would result in an extent ofdamage in excess of the above limit, then suchelements should be designed as a key elementas defined in paragraph 5.3 below.

e. For Class 3 buildings A systematicrisk assessment of the building should beundertaken taking into account all the normalhazards that may reasonably be foreseen,together with any abnormal hazards.

Critical situations for design should be selectedthat reflect the conditions that can reasonablybe foreseen as possible during the life of thebuilding. The structural form and concept andany protective measures should then be chosenand the detailed design of the structure andits elements undertaken in accordance withthe recommendations given in the Codes andStandards given in paragraph 5.2.

5.2 Details of the effective horizontal andvertical ties, together with the design approachesfor checking the integrity of the building followingthe notional removal of vertical members and

the design of key elements, are available in thefollowing Codes and Standards:

BS 5628-1:1992 Structural use of unreinforcedmasonry. Code of practice for use of masonry.

BS 5950-1:2000 Structural use of steelworkin building. Code of practice for design. Rolledand welded sections.

BS 8110-1:1997 Structural use of concrete.Code of practice for design and construction.

BS 8110-2:1985 Structural use of concrete. Codeof practice for special circumstances.

5.3 Definitions

Nominal length of load-bearing wall

The nominal length of load-bearing wallconstruction referred to in 5.1dshould be takenas follows:

in the case of a reinforced concrete wall, thedistance between lateral supports subject toa maximum length not exceeding 2.25H.

in the case of an external masonry wall, ortimber or steel stud wall, the length measuredbetween vertical lateral supports.

in the case of an internal masonry wall,or timber or steel stud wall, a length notexceeding 2.25H.

where H is the storey height in metres.

Key elements

A key element, as referred to in paragraph 5.1d,should be capable of sustaining an accidentaldesign loading of 34kN/m2applied in thehorizontal and vertical directions (in one directionat a time) to the member and any attachedcomponents (e.g. cladding etc.) having regardto the ultimate strength of such componentsand their connections. Such accidental designloading should be assumed to act simultaneouslywith 1/3 of all normal characteristic loading (i.e.wind and imposed loading).

Load-bearing construction

For the purposes of this Guidance the termload-bearing wall construction includesmasonry cross-wall construction and wallscomprising close centred timber or lightweightsteel section studs.

Alternative approach

5.4 Alternatively, for any building whichdoes not fall into the classes listed under Table11 or for which the consequences of collapsemay warrant particular examination of the risksinvolved, the performance may be met by therecommendations given in the following Reports:

Guidance on Robustness and Provision againstAccidental Actions dated July,1999.

Calibration of Proposed Revised Guidance onmeeting Compliance with the Requirements ofBuilding Regulation Part A3. Revision of theAllott and Lomax proposals. Project Report

No. 205966.

Both of the above documents are availableon the following ODPM websitehttp://www.odpm.gov.uk

REDUCING THE SENSITIVITY OF THE BUILDING TOA3 DISPROPORTIONATE COLLAPSE IN THE EVENT OF AN ACCIDENT


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Diagram 24 Area at risk of collapse in the event of an accident

See para 5.1d

REDUCING THE SENSITIVITY OF THE BUILDING TODISPROPORTIONATE COLLAPSE IN THE EVENT OF AN ACCIDENT A3


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A1/2

BS 187:1978Specification for calcium silicate (sandlime andflintlime) bricks. AMD 5427 1987.

BS 1243:1978Specification for metal ties for cavity wallconstruction. AMD 3651 1981, AMD 4024 1982.(Withdrawn and superseded by BS EN 845-1:2003Specification for ancillary components for masonry.Ties, tension straps, hangers and brackets.AMD 14736 2003.)

BS 5080-1:1993Structural fixings in concrete and masonry.Method of test for tensile loading.

BS 5268-2:2002Structural use of timber. Code of practicefor permissible stress design, materials and

workmanship.

BS 5268-3:1998Structural use of timber. Code of practice fortrussed rafter roofs.

BS 5628-1:1992Code of practice for use of masonry. Structuraluse of unreinforced masonry. AMD 7745 1993,AMD 13680 2002.(Withdrawn and superseded by BS 5628-1:2005Code of practice for the use of masonry. Structuraluse of reinforced masonry.)

BS 5628-2:2000

Code of practice for use of masonry. Structuraluse of reinforced and prestressed masonry.(Withdrawn and superseded by BS 5628-2:2005Code of practice for the use of masonry. Structuraluse of reinforced and prestressed masonry.)

BS 5628-3:2001Code of practice for use of masonry. Materialsand components, design and workmanship.(Withdrawn and superseded by BS 5628-3:2005Code of practice for the use of masonry. Materialsand components, design and workmanship.)

BS 5950-1:2000

Structural use of steelwork in building. Code ofpractice for design. Rolled and welded sections.AMD 13199 2001.

BS 5950-2:2001Structural use of steelwork in building.Specification for materials, fabrication anderection. Rolled and welded sections.

BS 5950-3-1:1990Structural use of steelwork in building. Design incomposite construction. Code of practice for designof simple and continuous composite beams.

BS 5950-4:1994

Structural use of steelwork in building. Codeof practice for design of composite slabs withprofiled steel sheeting.

BS 5950-5:1998Structural use of steelwork in building. Codeof practice for design of cold formed thingauge sections.

BS 6399-1:1996

Loading for buildings. Code of practice for deadand imposed loads. AMD 13669 2002.

BS 6399-2:1997Loading for buildings. Code of practice for windloads. AMD 13392 2002, AMD 14009 2002.

BS 6399-3:1998Loading for buildings. Code of practice forimposed roof loads. AMD 6033 1988, AMD 91871996, AMD 9452 1997.

BS 8002:1994Code of practice for earth retaining structures.AMD 8851 1995, AMD 12062 2001,

AMD 13386 2001.BS 8004:1986Code of practice for foundations.

BS 8103-1:1995Structural design of low-rise buildings. Codeof practice for stability, site investigation,foundations and ground floor slabs for housing.AMD 8980 1995.

BS 8103-2:1996Structural design of low-rise buildings. Code ofpractice for masonry walls for housing.(Superseded but remains current by BS 8103-2:2005

Structural design of low rise buildings. Codeof practice for masonry walls for housing, butremains current.)

BS 8103-3:1996Structural design of low-rise buildings. Code ofpractice for timber floors and roofs for housing.

BS 8103-4:1995Structural design of low-rise buildings. Code ofpractice for suspended concrete floors for housing.

BS 8110-1:1997Structural use of concrete. Code of practicefor design and construction. AMD 9882 1998,

AMD 13468 2002.BS 8110-2:1985Structural use of concrete. Code of practicefor special circumstances. AMD 5914 1989,AMD 12061 2001.

BS 8110-3:1995Structural use of concrete. Design charts forsingly reinforced beams, doubly reinforced beamsand rectangular columns. AMD 5918 1989.

BS 8118-1:1991Structural use of aluminium. Code of practicefor design. AMD 10485 1999.

BS 8118-2:1991Structural use of aluminium. Specificationfor materials, workmanship and protection.AMD 10486 1999.

A

Standards referred to


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