Bs 7916 Osb Board

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BRITISH STANDARD BS 7916:1998

ICS 79.060.20

NO COPYING WITHOUT BSI PERMISSION EXCEPT AS PERMITTED BY COPYRIGHT LAW

Code of practice for the

Selection and application ofparticleboard, oriented strandboard (OSB), cement bondedparticleboard and woodfibreboards for specificpurposes

This British Standard, havingbeen prepared under thedirection of the Sector Board forBuilding and Civil Engineering,was published under theauthority of the Standards Boardand comes into effect on15 May 1998

BSI 1998

The following BSI referencesrelate to the work on thisstandard:Committee reference B/541Draft for comment 97/100111 DC

ISBN 0 580 29526 5

BS 7916:1998

Amendments issued since publication

Amd. No. Date Text affected

Committees responsible for thisBritish Standard

The preparation of this British Standard was entrusted to Technical CommitteeB/541, Wood-based panels, upon which the following bodies were represented:

Apa Engineered Wood Association

Association of British Plywood & Veneer Manufacturers

British Woodworking Federation

Council of the Forest Industries of British Columbia

Department of the Environment (Building Research Establishment)

Flat Roofing Contractors' Advisory Board

Forestry Commission

Furniture Industry Research Association

Institution of Structural Engineers

Local Authority Organizations

Mineral Bonded Board Products Federation

National Federation of Roofing Contractors

National House-Building Council

National Panel Products Association

Royal Institution of British Architects

Structural Board Association

Timber Research and Development Association

Timber Trade Federation

Wood Panel Industries Federation

Zurich Municipal Building Guarantee

BS 7916:1998

BSI 1998 i

Contents

Page

Committees responsible Inside front cover

Foreword ii

1 Scope 1

2 References 1

3 Definitions 1

4 Handling, stacking, storage and conditioning of boards and safetyconsiderations 2

5 Selection and application of particleboard, oriented strand board (OSB)and cement bonded particleboard 5

6 Application of boards in non-domestic flooring 9

7 Application of boards in sheathing 11

8 Application of boards in flat roofing 11

9 Application of boards in pitched roofing 14

10 Application of boards in furniture and built-in fitments 14

11 Selection and use of wood fibreboards 16

12 Grades 16

13 Selection of material 16

Annex A (informative) Nearest fit comparison between British Standard boarddesignations and European Standard designations 20

Annex B (informative) Determination of punching shear (concentrated load) 22

Bibliography 24

Figure 1 Stacking of boards 3

Figure 2 Positioning of boards over joists 8

Figure B.1 Layout of punching shear test rig 23

Table 1 Approximate equilibrium moisture content for different types ofboard 4

Table 2 Types and grades of particleboard, OSB and cement bondedparticleboard 5

Table 3 Selection of boards according to category for domestic flooring 6

Table 4 Joist or batten centres 6

Table 5 Selection of materials for non-domestic flooring according tocategory of use 10

Table 6 Selection of materials for use in flat roofing according to categoryof use 12

Table 7 Maximum recommended centres of support for materials used inflat roofs 13

Table 8 Centres of support for materials used for lining a pitched roof oftiles or slates 14

Table 9 Selection of material for use in furniture or fitments 15

Table 10 Types and grades of wet and dry process wood fibreboard 17

Table 11 Guidance on the use of wood fibreboards in construction 18

Table A.1 Particleboard 20

Table A.2 Oriented strand board 20

Table A.3 Cement bonded particleboard 20

Table A.4 Wood fibreboards 21

ii BSI 1998

BS 7916:1998

Foreword

This British Standard has been prepared by Technical Committee B/541. Itsupersedes BS 5669-5:1993, which is withdrawn.

Since being superseded by a group of BS ENs, BS 1142 and BS 5669-1, -2, -3 and -4have been declared obsolescent and will eventually be withdrawn, effectively makingBS 5669-5 unusable. The new BS EN specifications for fibreboards, particleboards,oriented strand boards (OSB) and cement bonded particleboards, which have alreadyreplaced the obsolescent standards, do not at present have any companion documentsgiving guidance on the selection and application of the specified materials, or on thecorrect methods for storing and handling them before use.

In view of this, the Technical Committee and user bodies such as the Department ofthe Environment, Trade and the Regions (DETR), architects, regulatory bodies andbuilding insurers considered that a companion code of practice for the BS ENs wasessential to ensure that the newly specified materials were correctly selected andapplied. This British Standard is intended to fulfil that role; however, it is recognizedthat a comprehensive revision of this standard will be required when a new packageof European Standards, giving guidance on the performance of wood-based panelsused in the construction of floors, walls and roofs, becomes available. Each of theseEuropean Standards comprises three parts: specification, requirements and testmethods. These documents are at present European pre-Standards undergoing publicenquiry.

The BS EN specifications referred to in this standard require fewer characteristics thanBS 5669-2, -3 and -4 and BS 1142. In some cases, therefore, recommended performancelevels are proposed for additional properties (for example hard body impactresistance). The values for such properties are determined by the appropriate BS ENmethod of test, referred to in the relevant clause and the list of references.

A British Standard does not purport to include all the necessary provisions of acontract. Users of British Standards are responsible for their correct application.

Compliance with a British Standard does not of itself confer immunityfrom legal obligations.

Summary of pages

This document comprises a front cover, an inside front cover, pages i and ii, pages 1 to24, an inside back cover and a back cover.

BSI 1998 1

BS 7916:1998

1) Sometimes referred to as wood chipboards.2) Repeated from BS EN 309.3) Repeated from BS EN 300.4) Repeated from BS EN 633.5) Repeated from BS EN 316.

1 ScopeThis British Standard gives recommendations for thestorage, handling, selection and application of thefibreboards, particleboards1), oriented strand boards(OSB) and cement bonded particleboards definedand specified in the following standards: BS EN 316,BS EN 622-1, -2, -3, -4 and -5, BS EN 309,BS EN 312-1, -2, -3, -4, -5, -6 and -7, BS EN 300,BS EN 633 and BS EN 634-1 and -2.

NOTE The guidance given on the selection and use offibreboards is restricted to construction uses.

2 Normative ReferencesThe following normative documents containprovisions which, through reference in this text,constitute provisions of this British Standard. Fordated references, subsequent amendments to, orrevisions of, any of these publications do not apply.For undated references, the latest edition of thepublication referred to applies.

3 Terms and definitionsFor the purposes of this British Standard, thefollowing terms and definitions apply.

3.1

particleboard2)

panel material manufactured under pressure andheat from particles of wood (wood flakes, chips,shavings, sawdust, wafers, strands and similar)and/or other lignocellulosic material in particle form(flax shives, hemp shives, bagasse fragments andsimilar) with the addition of an adhesive

3.2

oriented strand board (OSB)3)

multi-layered board made from strands of wood of apredetermined shape and thickness together with abinder. The strands in the external layers are alignedand parallel to the board length or width; the strandsin the centre layer or layers may be randomlyoriented, or aligned, generally at right angles to thestrands of the external layers

3.3cement bonded particleboard4)

sheet material manufactured under pressure, basedon wood or other vegetable particles bound withhydraulic cement and possibly containing additives

3.4wood fibreboard5)

panel material with a thickness of 1,5 mm andgreater, manufactured from lignocellulosic fibreswith application of heat and/or pressure. The bond isderived from either:

the felting of the fibres and their inherentadhesive properties; or from a synthetic binder added to the fibres.

Other additives may be included

3.5 wet process fibreboards5)

fibreboards having a fibre moisture content of morethan 20 % at the stage of forming. The followingtypes are differentiated, according to their density:

3.5.1softboards5)

(density < 400 kg/m3)these fibreboards have thermal and acousticproperties. They can be given additional properties,e.g. fire retardance, moisture resistance

3.5.2medium boards5)

(density $ 400 kg/m3 < 900 kg/m3) low density medium boards(400 kg/m3 < 560 kg/m3) high density medium boards(560 kg/m3 < 900 kg/m3)

they can be given additional properties, e.g. fireretardance, moisture resistance

3.5.3hardboards5)

(density $ 900 kg/m3)they can be given additional properties, e.g. fireretardance, moisture resistance, resistance againstbiological attack, workability (e.g. mouldability)

3.6dry process fibreboards (MDF)5)

fibreboards having a fibre moisture content of lessthan 20 % at the forming stage, and having a densityof $ 600 kg/m3.So-called medium density fibreboards (MDF) areproduced with a synthetic adhesive under heat andpressure.They can be given additional properties, e.g. fireretardance, moisture resistance, resistance againstbiological attack

2 BSI 1998

BS 7916:1998

3) Repeated from BS EN 300.6) Repeated from BS EN 622.7) Repated from BS EN 335-1.

3.7

major axis3)

direction in the plane of the board in which thebending properties have the higher values

3.8

minor axis3)

direction in the plane of the board at right angles tothe major axis

3.9

dry conditions6)

conditions (defined in terms of service class 1 ofENV 1995-1-1 for load-bearing boards) characterizedby a moisture content of the material correspondingto a temperature of 20 C and a relative humidity ofthe surrounding air exceeding 65 % only for a fewweeks per year. Boards of this type are suitable foruse only in biological hazard class 1 of EN 335-3

3.10

humid conditions6)

conditions (defined in terms of service class 2 ofENV 1995-1-1 for load-bearing boards) characterizedby a moisture content of the material correspondingto a temperature of 20 C and a relative humidity ofthe surrounding air exceeding 85 % only for a fewweeks per year. Boards of this type are suitable foruse only in biological hazard classes 1 and 2 ofEN 335-3

3.11

exterior conditions6)

weathering conditions, liquid water or water vapourin a damp but ventilated location. Boards of this typeare suitable for use in biological hazardclasses 1, 2 and 3 of EN 335-3. (Defined in terms ofservice class 3 of ENV 1995-1-1 for load bearingboards.)

3.12

general purpose use6)

all non-load bearing applications, e.g. furniture andfitments

3.13

load-bearing use6)

use in a load-bearing construction, i.e. an organizedassembly of connected parts designed to providemechanical resistance and stability to the works(see BS 5268-2 or DD ENV 1995-1-1 and/orperformance standards)

3.14

biological hazard class 17)

situation in which the wood or wood-based productis under cover, fully protected from the weather andnot exposed to wetting

3.15biological hazard class 27)

situation in which the wood or wood-based productis under cover and fully protected from the weatherbut where high environmental humidity can lead tooccasional but not persistent wetting


situation in which the wood or wood-based productis not covered and not in contact with the ground. Itis either continually exposed to the weather or isprotected from the weather but subject to frequentwetting


situation in which the wood or wood-based productis in contact with the ground or fresh water and thusis permanently exposed to wetting

3.18damp proof membranelayer or sheet of material within a floor or similarconstruction, or vertically within a wall, to preventpassage of moisture

3.19vapour control layerlayer of material restricting the transmission ofvapour

4 Handling, stacking, storage andconditioning of boards and safetyconsiderations4.1 GeneralThe recommendations given in 4.2 to 4.5 arefundamental to avoid damage, distortion, ordegradation of boards during transit or storage and itis essential that they are followed.

4.2 Transport and deliveryBoards should be adequately protected by awaterproof covering during all transportation. It isparticularly important that the edges are wellcovered.The edges of boards should be fully protected so asto prevent damage by lashings or other banding.Boards should be loaded so as to avoid distortion intransit (see 4.4). Details of board type and quantityshould accompany each delivery.

4.3 HandlingThe most vulnerable parts of the boards are theiredges and corners. Even if the boards are to befurther trimmed before use, they should be carefullyhandled and, if necessary, edges and corners shouldbe additionally protected on site. This particularlyapplies to profiled boards such as tongued andgrooved flooring. When handling boards it isessential to avoid any contamination of the surfacelikely to cause permanent damage or have anadverse effect on subsequent finishing or finishes.

BSI 1998 3

BS 7916:1998

a) Correct and incorrect method of storing boards on battens. b) Correct method of edge stacking.

c) Correct method of supporting and stacking boards with athickness of 6 mm or less.

d) Example of providing temporary protection(tarpaulin cover).

All dimensions in millimetres.

Figure 1 Stacking of boards

4.4 Stacking

Boards should be stacked flat, off the ground, andon a level surface with all four edges flush. Stackingon edge should be avoided wherever possible. Theideal base is a close-boarded or slatted pallet. If thisis not possible the board should be carefully stackedlevel on battens of equal thickness separated fromeach other by not more than 600 mm (see Figure 1a).

The top of the pile should be covered with somekind of protective board to prevent warping of thetopmost board. Intermediate bearers arerecommended every 10 to 15 boards and it isessential that the bearers are placed directly abovethose below. The ends of the battens should beequidistant from the long edges of the stack andparallel to the ends. Overhang of the boards at theedges and ends of the stack should notexceed 150 mm at any point.

Where boards are banded, the bands should be cutas soon as practicable after delivery to prevent themfrom permanently deforming the boards, which mayexpand due to moisture absorption.

Where space only permits edge stacking, the edgesshould not be permitted to come into direct contactwith the floor (see Figure 1b). The haphazard leaningof boards against walls should always bediscouraged. Where boards with a thickness of 6 mmor less are being stacked it is recommended thatsupport be provided for the entire area of the boardby placing a thicker board (at least 18 mm) at thebase of the pile (see Figure 1c).

4 BSI 1998

BS 7916:1998

Table 1 Approximate equilibrium moisture content for different types of board

Relative humidityat 20 C

Approximate equilibrium moisture content

Particleboard OSB Cement bondedparticleboard

Wood fibreboards

% % % % %

30 7 5 5 5

65 11 10 10 8

85 15 15 14 12

8) SI 1994 No. 3246

4.5 Storage and conditioning

Boards expand on taking up moisture from thesurrounding air and shrink on losing it. The boardslisted in Tables 2 and 10 are manufactured todimensional tolerances allowing close fits to beachieved on jointing and placing the boards intoposition. Careful storage is therefore very importantif the boards are to be maintained in the correctcondition for their subsequent use.

All boards should be protected from rain andaccidental soaking.

Only when boards are required for conditioningshould any protective wrapping be removed. Wherethe boards are to be used in warm, dry areas themoisture content should be kept as low as possibleto avoid unacceptable shrinkage after installation.The moisture content of the boards when they leavethe factory ranges from 2 % to 13 %. Table 1 gives theapproximate equilibrium moisture content fordifferent board types stored under different relativehumidities of the surrounding air.

These levels can only be taken as a general guideand will vary with type and density of board.Long-term storage in damp conditions can causedamage to the surface and edges of the boards.Boards should therefore be stored in an enclosed drybuilding. Where temporary storage outside cannot beavoided, the stacks should be covered withpolyethylene or a tarpaulin, keeping all boards wellclear of the ground (see Figure 1d).

NOTE Boards gradually attain the moisture content dictated bythe atmosphere within the building. Although it is not possible togive precise levels, the following figures give a general indicationof the range of moisture content of boards under variousconditions:

a) continuously heated building: 7 % to 9 %;

b) intermittently heated building: 9 % to 12 %;

c) unheated new building: up to 15 %.

Any increase in moisture content causes slight expansion in theboards and, although this also cannot be precisely defined, as arough guide, an increase in moisture content of 1 % increaseslength and width by 0.3 mm per metre run for particleboard andOSB and 0.4 mm per metre run for wet and dry processfibreboards, and by 0.05 mm per metre run for cement bondedparticleboard.

Design precautions necessary to accommodatemovement of board are given in 5.5, 6.3, 7.3, 8.3and 9.2, but wherever possible boards should beallowed to reach equilibrium conditions by storingthem under the atmospheric conditions in whichthey are to be used. It is recommended that theboards are air conditioned by stacking each boardwith separators in between to allow free circulationof air.

Conditioning in air is suitable for most board typesand applications. Where higher humidities may occurafter fixing, it is recommended that hardboards andsome wet process mediumboards are conditionedwith water prior to laying. In this method, water isbrushed into the mesh face of each board and theboards then stacked mesh face to mesh face for aprescribed time. Water conditioning is unsuitable forparticleboards, OSB, dry process fibreboards andcertain pre-treated boards, such as flame retardantand predecorated boards.

4.6 Safety

Persons using these materials should be familiar withnormal industrial practice.

This code of practice does not purport to address allthe safety issues associated with the normal use ofwood-based panels.

It is the responsibility of the user to establish healthand safety practices when storing or handling thesematerials which will ensure compliance withUK regulations. These are principally the Control ofSubstances Hazardous to Healthregulations 1994 (COSHH)8) [1], and especiallyregulations 6, 7-(6) and 10; although all theregulations are relevant.

The principal hazardous substances associated withthe storage and use of wood-based panels are wooddust, produced by cutting, drilling and sanding, andformaldehyde. The latter is only a significantconsideration in respect of certain particleboardsand MDF. Both substances are subject to maximumexposure limits (MEL).

The MEL's are only likely to be realized if materialsare worked in poorly ventilated areas, or, in the caseof formaldehyde, if very large amounts of panels arestored in hot, confined or poorly ventilated spaces.

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BS 7916:1998

Table 2 Types and grades of particleboard, OSB and cement bonded particleboard

Board type Grade References

Particleboard

General purpose (for use in dry conditions) P2 BS EN 312-2

Boards for interior fitments (including furniture) (for use in dry conditions) P3 BS EN 312-3

Load bearing (for use in dry conditions) P4 BS EN 312-4

Load bearing (for use in humid conditions) P5 BS EN 312-5

Heavy duty load bearing (for use in dry conditions) P6 BS EN 312-6

Heavy duty load bearing (for use in humid conditions) P7 BS EN 312-7

Oriented strand board

General purpose and boards for interior fitments (including furniture)(for use in dry conditions)

OSB/1 BS EN 300

Load bearing (for use in dry conditions) OSB/2 BS EN 300

Load bearing (for use in humid conditions) OSB/3 BS EN 300

Heavy duty load bearing (for use in humid conditions) OSB/4 BS EN 300

Cement bonded particleboard

OPC (ordinary Portland cement) (for use in dry, humid and exteriorconditions)

BS EN 634-2

5 Selection and application ofparticleboard, oriented strand board(OSB) and cement bondedparticleboard

5.1 General

Clause 5 gives guidance on selection and applicationof the types and grades of particleboard, OSB andcement bonded particleboard which can beconsidered for use in certain applications. Onlycommon uses in the construction industry in thecase of particleboard, OSB and cement bondedparticleboad, and use in furniture and built-infitments are covered. It is not intended that the useof the materials is restricted solely to theseapplications.

Additional guidance on the use of boards in specificapplications can be found in the codes and standardsreferred to in this clause.

NOTE Until such time as the introduction of appropriateEuropean Standards, grade references given in other BritishStandards referred to in this standard will need to be substitutedwith the relevant grades as listed in 5.3.1, 6.1, 7.1, 8.1, 9.1 and10.2. Comparative guidance is given in annex A.

5.2 Grades

Table 2 shows the types and grades ofparticleboards, OSB and cement bondedparticleboards specified in the BS ENs referred to inthis standard.

5.3 Application of boards in domestic flooring

5.3.1 Selection of material

It is essential that the materials used in suspended orfloating floors or overlayments in domestic premisesbe selected from the following, according to thecategory of use described in Table 3:

a) particleboards P5 conforming toBS EN 312-5 and P7 conforming to BS EN 312-7;

b) oriented strand board, type OSB/2, OSB/3 orOSB/4 conforming to BS EN 300;

c) cement bonded particleboard conforming toBS EN 634-2.

NOTE Oriented strand board should not be used as the floatingoverlay board on a continuously supported floating floor (5.3.3.1).

6 BSI 1998

BS 7916:1998

Table 3 Selection of boards according to category for domestic flooring

Conditions of use Material

Particleboard OSB Cement bondedparticleboard

Installed dry, with no risk of wetting inservice

P5, P7 OSB/2, OSB/3, OSB/4 Suitable

Risk of wetting during installation or risk ofoccasional wetting or condensation inservice

P5, P7 OSB/3, OSB/4 Suitable

Table 4 Joist or batten centres

Dimensions in millimetres

Material Maximuma joist/batten centres for different material thicknesses

15 mm 18/19 mm 22 mm

Particleboard types P5 and P7 450 610

OSB/22) 450 610

OSB/32), OSB/42) 450 610

Cement bonded particleboard 450 610a See 5.4.2.

b It is essential that OSB is laid with the major axis (indicated on the board) at right angles to the support. (See 5.4.2.)

9) See type A (self-contained dwelling units) in Table 1 of BS 6399-1:1996.

5.3.2 Hard body impact resistance

It is essential that materials used in domesticflooring have adequate impact resistance. Whentested in accordance with BS EN 1128, in both thejointed or un-jointed mode, all the materials listedin 5.3.1a), b) and c) should have a resistance to hardbody impact of not less than 500 mm drop height.NOTE Hard body impact resistance does not form part of thespecification of any of these materials. Verification of compliancewith this property should therefore be obtained from the supplier.

5.3.3 Design

5.3.3.1 Boards on continuous support

Material for boards on continuous support should beselected from those listed in 5.3.1. The thickness ofboards used for this application is related to thestiffness and compressive strength of the continuousunderlay.

5.3.3.2 Boards on joists or battens

The joist or batten spacings given in Table 4 aremaximum values for a uniformly distributed loadof 1.5 kN/m2.9)

5.4 Laying and fixing

5.4.1 Boards on continuous support

Before laying a continuously supported floating floor,it is essential that the subfloor is adequatelyprepared. Surface regularity should be class SR2 orbetter to BS 8204-1, i.e. maximum 5 mm deviationfrom under a 3 m straight edge. Particular attentionshould be paid to movement joints and to screed andbay junctions so as to avoid undulations and othersurface irregularities.

Pre-cast concrete floors should have a level flatsurface. If deviations occur a levelling screed may berequired.

In all cases where boards are used over in situconcrete floor construction, a damp proof membrane(DPM) should be positioned over the slab to protectthe floor deck from residual moisture.NOTE 1 A DPM above the slab may not be necessary if there is aDPM below the slab and the slab moisture content has beendetermined as being below 5 %. With polymer modified concreteand screeds, the guidelines of drying times of one month foreach 25 mm of slab thickness cannot be relied on. Even if thesurface appears dry, moisture can still be retained inside theconcrete or screed.

NOTE 2 Although pre-cast concrete floors are essentially dry,protection with a vapour control layer (on all floor levels) isneeded to protect against residual moisture resulting fromconstruction or exposure to weather.

Special care should be taken to ensure that boardsare laid in a dry condition after all wet siteoperations such as plastering have been completed.In dry construction, e.g. timber frame, the overlayfloor should only be installed as a working platformonce the building is watertight. After laying, the floorshould be protected from dirt and moisture. Anyfactory applied protective layer should be retained inplace for as long as possible.

A moisture and vapour control layer providing aresistance to water vapour permeability of atleast 200 MNs/g e.g. a minimum thickness of 250 mm(1000 gauge) should be laid above the insulationlayer and should be upturned by at least 38 mmaround perimeter walls. Any joints in the sheetshould be lapped by at least 150 mm and the jointstaped with a vapour resistant tape.

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BS 7916:1998

Proprietary composite floor panels with pre-bondedplastics insulation of not less than 25 mm have arelatively high vapour resistance, and it is thereforeacceptable to locate the vapour control layerbeneath the insulation.

Joints along the shorter edges should be staggered.

It is essential that all tongued and grooved joints areglued.

5.4.2 Boards on a self-supporting floating floor(with battens)

Timber battens should be preservatively treated inaccordance with BS 5589. Battens should have amoisture content not exceeding 20 %. Where battenshave been treated with a water-borne preservativethey should be re-dried to a moisture content notexceeding 20 %.

Battens should not be less than 47 mm wide and thedepth should be greater than the insulation thicknessto allow for shrinkage of the batten resulting fromdrying to its equilibrium moisture content. Battensshould be placed at appropriate centres(see 5.3.3.2).

Before laying the battens, the sub-floor should beadequately prepared, and moisture conditionssatisfied, as described in 5.4.1. Any gaps beneath thebattens caused by unevenness in the sub-structureshould be packed with a durable material(e.g. preservatively treated timber, temperedhardboard, dry mix sand and cement mortar).Flooring systems designed for acoustic performancemay utilize resilient materials.

A moisture and vapour control layer providing aresistance of at least 200 MNs/g e.g. a minimumthickness of 250 mm (minimum 1000 gauge) should belaid above the battens and insulation layer andshould be upturned by at least 38 mm aroundperimeter walls. Any joints in the sheet should belapped by at least 150 mm and the joints taped with avapour resistant tape.

5.4.3 Positioning and fixing boards over joistsand battens

It is essential that square-edged boards are supportedcontinuously along all edges. This is best achievedfor particleboards and for cement-bondedparticleboards by positioning them with their longeredges butt-jointed on the centreline of a joist orbatten and supporting the short edges by noggings orcounter-battens (see Figure 2a).

Tongued and grooved boards should be laid withtheir longer edges across the supports. It is essentialthat the joints between the shorter edges aresupported along the centreline of a joist or batten.To avoid the need for additional support the joistcentres used may need to be less than those given inTable 4 to accommodate the actual boarddimensions. Support under the long edges of tonguedand grooved boards between correctly spaced joistsis not required.

For both square edged and tongued and groovedOSB it is essential that they are laid with their longedges across the joists (see Figure 2b) since they arestronger parallel to the major axis (see 3.7).Additionally, for square edged OSB, it is essentialthat the long edges are supported by noggings(not shown in Figure 2b).

When using all types of either square edged ortongued and grooved boards, joints along the shorteredges should be staggered and the board lengthshould generally be not less than two joist spacings.It is essential that edges around the perimeter of thefloor are continuously supported, either on joists ornoggings.

8 BSI 1998

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a) Square-edged boards (other than OSB)

b) Tongued and grooved boards and square edged OSB.

NOTE 1 A similar arrangement applies to boards laid over battens.

NOTE 2 In the case of square edged OSB it is essential that the long edges aresupported by noggings (not shown).

Figure 2 Positioning of boards over joists

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10) See BS 5268-2.

5.4.4 Fixing

All boards should be fastened firmly to joists,battens or, when used as an overlayment, to anexisting timber floor (see BS 8201). Flat headed ringshanked nails (3 mm in diameter) or screws shouldbe used. Unless modified screws are used, theyshould be inserted through pre-drilled andcountersunk clearance holes. Their length should benot less than 2.5 3 thickness of the board. Unlesspower nailing is used, cement boundedparticleboards greater than 12 mm in thicknessshould be pre-drilled before nailing. When fixingboards to a steel supporting framework, self-tappingscrews of not less than 4 mm diameter should beused. The screw point should extend at least 13 mmbelow the underside of the steel support.

Fastenings should be spaced at centres not morethan 300 mm apart along both the continuouslysupported edges and the intermediate supports.Fastenings should be at least 8 mm from the edge ofthe board. Nail heads should be punched 2 mmto 3 mm below the surface of the board and screwsshould be countersunk. Boards should be glued tothe joists and tongued and grooved joints shouldalso be glued.

To reduce the risk of creaking, the moisture contentof timber joists should be as near as possible to theservice condition10) when the boards are fixed.

NOTE Polyvinyl acetate (PVAC) adhesive conforming to at leastdurability class D1 of BS EN 204 is satisfactory for gluing tonguedand grooved joints, and boards to joists.

5.5 Allowing for movement

It is necessary to allow for possible expansion byproviding a gap whenever boards abut any rigidupstand such as a perimeter wall, column orfireplace surround. This gap should be not lessthan 10 mm wide. Large floors may need a wider gapand intermediate expansion gaps to allow for apossible overall expansion of 2 mm per metre lengthof floor. The expansion gaps should be either:

a) left open and masked by a skirting or loosecover strip; or

b) filled with an easily compressible material, suchas cork.

It is essential that they are kept free from plaster,mortar droppings and other debris duringconstruction.

NOTE Although expansion is the most usual movementencountered, shrinkage can occur in areas with higher thanaverage temperatures, e.g. nursing homes, hospitals etc. (See 4.5.)

6 Application of boards innon-domestic flooring

6.1 Selection of material

6.1.1 Suitable board types

It is essential, when selecting boards from thoselisted below, that the conditions of use given inTable 5 are carefully considered. ParticleboardsP4, P6 and OSB/2 should not be used where there isa possibility of their becoming wet in service.

The following are suitable board types:

a) particleboard P4, conforming to BS EN 312-4,P5 conforming to BS EN 312-5, P6 conforming toBS EN 312-6 or P7 conforming to BS EN 312-7;

b) oriented strand board type OSB/2, OSB/3 orOSB/4, conforming to BS EN 300;


NOTE Oriented strand board should not be used as the floatingoverlay board on a continuously supported floating floor.

6.1.2 Impact resistance

It is essential that materials used in flooring orspecial floor construction with restricted deflectionhave adequate impact resistance for the intended enduse.

6.1.3 Punching shear (concentrated load)

BS 6399-1 lists floor loadings appropriate to differentoccupancy classes of buildings (e.g. residential,office, retail, industrial, public assembly andstorage). Designers should be aware of the specialproblems in use that may relate to boards in order tosatisfy certain concentrated load requirements.

If required by a design, the punching shear capacityof the selected board type should be determined bytesting in accordance with the method described inannex B. The design value based on the test resultsmay be derived by applying the procedures andfactors given in the National ApplicationDocument, 6.2 of DD ENV 1995-1-1:1994.

10 BSI 1998

BS 7916:1998

Table 5 Selection of materials for non-domestic flooring according to category of use

Category Design requirements Clause Conditions of use

Dry installation Risk of wettingduring

installation andrisk of

occasionalwetting in

service

Risk of regularwetting in

service

1. Floating-floorconstructions inwhich boards arecontinuouslysupported

No risk of personal injury in the event offloor failure

6.2.1 P4, P5, P6, P7 P5, P7 Cement bondedparticleboard

OSB/2,OSB/3,OSB/4

OSB/3, OSB/4

Cement bondedparticleboard


2. Compositefloors in which theboard is onlypartially loadbearing

Subject to compliance with performancetesting using appropriate loadings inBS 6399-1 and designed in accordancewith prototype testing as defined inBS 5268-2


OSB/2, OSB/3OSB/4

OSB/3, OSB/4



3. Light dutysuspended floors(including floatingbattened floorswith discontinuoussupport)Restricted touniformlydistributed load#2.5 kN/m2 andconcentrated load#2.7 kN

Minimum board thickness 22 mmat 400 mm joist centres

6.2.3 P4, P5, P6, P7 P5, P7 Not suitable

Minimum board thickness 18 mmat 400 mm joist centres

6.2.3 OSB/2,OSB/3,OSB/4

OSB/3, OSB/4 Not suitable

Subject to compliance with performancetesting using the appropriate loadings inBS 6399-1 and designed in accordancewith prototype testing as defined inBS 5268-2


OSB/2, OSB/3,OSB/4

OSB/3, OSB/4



4. Heavy dutysuspended floors(e.g. warehouses,storage areas andmezzanine floors)Uniformlydistributed load>2.5 kN/m2 andconcentrated load>2.7 kN

Until structural design values are available, recourse should be made to prototype testing in accordance withBS 5268-2. Only those materials which meet the design criteria in such tests may be used.

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BS 7916:1998

6.2 Design

6.2.1 Floating floor constructions in whichboards are continuously supported

NOTE See category 1 in Table 5.

Materials should be selected from those listedin 5.3.1. The thickness of boards used for thisapplication is related to the stiffness andcompressive strength of the continuous underlay.

6.2.2 Composite floors incorporating woodbased panels, e.g. platform floors and accessfloors


For composite floors it is recommended that type P4,P5, P6 or P7 particleboard, type OSB/2, OSB/3 orOSB/4, or cement bonded particleboard should beused. Where there is a risk of wetting duringinstallation or occasional wetting in service, onlytype P5 or P7 particleboard, type OSB/3, OSB/4, orcement bonded particleboard are recommended.

6.2.3 Light duty suspended floors includingfloating battened floors with discontinuoussupport

General offices (see type B; general offices and workareas not considered elsewhere) are defined inTable 1 of BS 6399-1:1996 in terms of a maximumuniformly distributed load no greater than 2.5 kN/m2

and a concentrated load no greater than 2.7 kN.


For light duty suspended floors, it is recommendedthat type P4, P5, P6 or P7 particleboard or typeOSB/3, OSB/4 should be used. Where types P4 orP5 particleboard are used, it is essential that theminimum board thickness is not less than 22 mmwith a corresponding maximum joist spacingof 400 mm. Where OSB/3 or OSB/4 are used it isessential that board thickness should not be lessthan 18 mm. Where there is a risk of wetting duringinstallation or in service, only types P5 or P7particleboard, OSB/3, OSB/4 or cement bondedparticleboard are recommended.

6.2.4 Heavy duty suspended floors

Heavy duty suspended floors are defined in terms ofa maximum uniformly distributed load greaterthan 2.5 kN/m2 or concentrated load greaterthan 2.7 kN.


Until structural design values are available, recourseshould be made to prototype testing in accordancewith BS 5268-2. Only those materials which meet thedesign criteria in such tests may be used.

6.3 Laying and fixing

The recommendations of 5.4 relating to boardorientation, provision of gaps and gluing also applyto non-domestic floors.

7 Application of boards in sheathing


It is essential that materials used in timber framedwall sheathing be selected from the following:

a) particleboard P5 conforming to BS EN 312-5,or P7 conforming to BS EN 312-7;

b) oriented strand board type OSB/3, or OSB/4,conforming to BS EN 300;


7.2 Design

The racking resistance of boards should either be asgiven in Table 2 of BS 5268-6.1:1996 or obtained byload testing, in accordance with BS 5268-6.1.

7.3 Fabrication

Fabrication should be carried out in such a way thatany variations in panel dimensions, member sizes,sheathing and joint details are within the tolerancesgiven in BS 5268-6.1.

It is necessary to allow for possible expansion byproviding a 3 mm gap between adjacent boards anda 10 mm gap between the panel and any abutment.Long walls may need a wider gap and intermediateexpansion gaps to allow for a possible overallexpansion of 2 mm per metre length of wall. This isin addition to the 3 mm gap required for expansionbetween each individual panel.

7.4 Fire protection

Where mandatory regulations require restriction onthe spread of flame, such a requirement should beobserved.

8 Application of boards in flat roofing


It is essential that boards used as decks in flatroofing be selected from the following list accordingto the category of use given in Table 7:

a) particleboard P5 conforming to BS EN 312-5or P7 conforming to BS EN 312-7;

b) oriented strand board type OSB/2, OSB/3 orOSB/4 conforming to BS EN 300;


It is essential that materials used in the applicationsgiven in b) in Table 6 should have adequateresistance to hard body impact. For theseapplications the recommendations in 5.3.2 should befollowed.

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BS 7916:1998

Table 6 Selection of materials for use in flat roofing according to category of use

Roof types Particleboard OSB Cement bondedparticleboard

Warm deck

a) Flat roofs to buildings where the roof insulationoccurs above the supporting deck and the thermaldesign is such that it substantially eliminates thepossibility of condensation within the roof P5, P7 OSB/3, OSB/4

b) Flat roofs to buildings where the roof insulationoccurs above the supporting deck but the thermaldesign does not eliminate the possibility ofcondensation or where occupancy conditions arelikely to lead to high levels of humidity

Should not beused

Should not beused Suitable for all

roof typesCold deck

c) Flat roofs to small garages and other similarunoccupied small buildings without a ceiling P5, P7

OSB/2, OSB/3,OSB/4

d) Flat roofs to buildings where the insulationoccurs below the supporting deck and adequatethrough ventilation of the void between theinsulation and the deck is provided, where a vapourcheck at ceiling level is installed and where highhumidity conditions are not likely to occur P5, P7 OSB/3, OSB/4

NOTE The different occupancy of compartments under a common roof should be taken into account in determining the humidity tobe used in the assessment. For example, where there is adequate cross ventilation between compartments, the occupancy humidityshould be obtained by assessing that prevailing in each compartment in proportion to the roof areas of the compartments.

8.2 Design

It is essential that the maximum span between joistsfor boards of different thicknesses is not greaterthan the values given in Table 7.

The values in Table 7 are given on the assumptionthat the roof will be constructed in accordance withaccepted design principles for weather resistance,leakage and control of condensation within the roof.If the roof construction necessitates the provision ofventilation, the design should be such as to create anunrestricted cross flow of air through the structure.The rate of ventilation depends on the design andoccupancy condition of the building, but should atleast meet the minimum recommendations ofBS 5250.

8.3 Laying

8.3.1 General

Laying and fixing instructions may differ dependingon the covering material to be used. The generalrecommendations given in 8.3.2 to 8.3.4 apply to themajority of flat roof constructions.

8.3.2 Protection of boards

During laying, materials should be protected fromthe weather and should be dry when theweatherproof membrane is applied. Alternatively,boards listed in 8.1 and protected withweather-resistant covering, such as prefelting, aresin-film overlay, or metal foil, may be selected inthis case.

It is essential that joints in boards already protectedwith a weather-resistant covering are taped on theday of laying. In this way a temporary protection canbe obtained without the need for further covering.The protective layer should not be regarded as partof a permanent water proofing specification.

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BS 7916:1998

Table 7 Maximum recommended centres of support for materials used in flat roofs


Application Boardthickness

Particleboarda OSBa Cementbonded

particleboardaTypes P5 and

P7Type OSB/2 Type OSB/3,

OSB/4

a) Roofs of small garages andsimilar buildings (without accessexcept for maintenance) 11 to 12 400

15 to 16 450 450 610 400

18 to 19 610 610 610 610

b) Roofs over habitable areaswhere access is provided(in addition to maintenance andrepair) 15 to 16 450 450

18 to 19 610 450

22 610 610 610

c) Roofs over habitable areaswhere no access is provided(other than that necessary formaintenance and repair) 11 to 12 450 300

15 to 16 610 450

18 to 19 450 610 450

22 610 610 610a indicates not suitable.

NOTE 1 Spans relating to use may alternatively be determined by design using the appropriate characteristic values given inprEN 12369 and modification factors in respect of load duration, strength and deflection given in DD ENV 1995-1-1.

NOTE 2 While it is accepted that the imposed loads in applications a) and c) are similar, site experience has shown that the thicknessquoted for garage and similar buildings provides an adequate construction in these lower risk situations.

NOTE 3 To avoid the need for additional support, the joist centres used may need to be less than those given above to accommodatethe actual board dimensions.

8.3.3 Positioning boards over joists

Boards should be positioned as recommendedin 5.4.3.

8.3.4 Fixing

Boards should normally be fixed directly to thesupporting structure by nailing at 100 mm centres.The lengths of the nails should be at least 2.53 theboard thickness. Boards should be fastened firmly tothe supporting structure. The wind uplift resistanceof fastenings should be checked where relevant. Flatheaded annular grooved nails (3 mm in diameter)and screws have superior holding power and shouldbe used in preference to plain shank nails. Unlesspower nailing is used, cement bonded particleboardsgreater than 12 mm thickness should be pre-drilledbefore nailing, or, alternatively, where screws areused, they should be inserted through pre-drilled andcountersunk clearance holes.

When fixing boards to a steel supporting framework,self-tapping screws of not less than 4 mm diametershould be used. The screw point should extend atleast 13 mm below the underside of the steelsupport.

Provision should be made for possible expansion ofthe boards by allowing a gap between the edges ofthe boards and the perimeter wall or other abutment.A gap should be provided at the rate of 2 mm permetre run. A perimeter gap of minimum width 10 mmshould be used.

In addition, for square edged boards, a gap of 3 mmshould be left around the perimeter of each board.

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BS 7916:1998

Table 8 Centres of support for materials used for lining a pitched roof of tiles or slates


Thickness Particleboard types P5 and P7 OSB/3, OSB/4 Cement bonded particleboard

8 to 9 610a 300

11 to 12 400 450 450

15 to 16 450 610 500

18 to 19 610 610 610a Suitable only where roof coverings (e.g. slates and tiles) are independently supported on battens, secured to counter battens. In allother cases, roof coverings may be attached directly to the board.

NOTE 1 Spans relating to the use of types P5 and P7 should be determined by design using the appropriate modification factors inrespect of load durations, strength and deflection given in DD ENV 1995-1-1.

NOTE 2 Where boards form part of a composite construction, the figures may vary in accordance with the manufacturer'srecommendations.

NOTE 3 To avoid the need for additional support, the joist centres used may need to be less than those given above to accommodatethe actual board dimensions.

9 Application of boards in pitchedroofing


It is essential that boards used in pitched roofsshould be selected from the following:

a) particleboard P5 conforming to BS EN 312-5,or P7 conforming to BS EN 312-7;

b) oriented strand board type OSB/3 or OSB/4,conforming to BS EN 300;


9.2 Design

Boards may be used in pitched roofs in one of thefollowing ways:

a) as a supporting decking to roof coverings inaccordance with 9.1 and Table 8;

b) as a lining to a roof of tiles or slates (sarking)in accordance with 9.1 and laid in accordancewith 8.3, where applicable, with the followingadditional recommendations:

1) suitable roof underlays in accordance withBS 5534:1997 should be laid over theparticleboard;

2) centres of support should not exceed thosegiven in Table 8.

Only cement bonded particleboard may be used inpitched roofs in continuously humid conditions.

10 Application of boards in furnitureand built-in fitments

10.1 Application categories

10.1.1 General

The two main application categories of use infurniture and built-in fitments are differentiated bythe surface and edging treatments applied to thematerials. Additional categories cover applicationsrequiring enhanced strength or improved resistanceto moisture.

10.1.2 Core boards

Within this category boards are used essentially ascore materials for the manufacture of panels. Theappearance, surface characteristics and stiffness inbending of the panels are determined largely by thepresence of relatively thick surfacing materials, suchas wood veneers and plastics laminates ofthickness 0.5 mm or greater.

The resistance of the panel edges to impact damageand the strength of joints between panels aredetermined largely by the presence of solid woodlippings of 10 mm thickness or greater bonded to theedges of the panels.

Typical applications include domestic table tops andpanels with moulded wood edges for use inreproduction furniture.

10.1.3 Panel boards

Within this category, the quality of the boards has amajor effect on the performance of the finishedpanels as the surfacing and edging materialscontribute little to strength properties. Panels to besurfaced with wood veneers, plastics laminates, foilsor liquid applied finishes with thicknesses lessthan 0.5 mm and panels edged with wood lippingsless than 10 mm width, or with strip edgingmaterials, are included in this category. Panels withpostformed edge treatments and wrapped mouldingsare also included, as a board with enhanced corestrength is required to ensure no breakout of coreparticles when the edges are profiled.

Typical applications include case goods, kitchenunits and shop fitments.

10.1.4 Boards with enhanced impact resistance

Boards used for some applications, such asupholstered chair frames, bed bases and chair seats,may require a high level of impact resistance inorder to resist certain types of damage associatedwith the manufacturing process or conditions of usein these items.

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BS 7916:1998

Table 9 Selection of material for use in furniture or fitments

Application/requirement Material types

Particleboard Oriented strand board Cement bonded particleboard

Core boards P3 OSB/1, OSB/2, OSB/3, OSB/4 Boards should be sanded

Panel boards P3 OSB/1, OSB/2, OSB/3, OSB/4 Boards should be sanded

Enhanced stiffness P3, P4, P5, P6, P7 OSB/1, OSB/2, OSB/3, OSB/4

Improved moistureresistance

P5, P7 OSB/3, OSB/4

10.1.5 Boards with enhanced stiffness inbending

Boards used for load bearing horizontal surfaces mayrequire enhanced stiffness in bending to limitdeflection in heavy duty applications.

Deflection limits for different use categories arespecified in BS 4875-7 and -8. In assessing therequirements of boards for these uses, account maybe taken of the stiffening effect of wood veneers,plastics laminates or other stiff surfacing materialsbonded to both faces. In addition to ensuring anacceptable maximum initial deflection, someallowance should be made at the design stage forsubsequent creep under sustained load conditions.

Typical applications include office storage systems,library book shelves and contract shelving systems.

10.1.6 Boards with improved moistureresistance

Wood-based panels used for applications where theymay be subject to intermittent wetting or prolongedexposure to conditions in excess of 85 % r.h. shouldbe constructed from boards with improvedresistance to moisture. Additionally, surface andedges should be adequately sealed to reduce the riskof water penetration.

Typical applications include kitchen worktops andbathroom fitments.

10.2 Selection of materials

It is essential that boards used for the constructionof furniture or fitments be selected from the typesgiven in Table 9.

10.3 Additional properties

10.3.1 General

Boards used for some furniture applications mayrequire additional characteristics to those covered bythe basic strength requirements. These are given in10.3.2 to 10.3.4.

10.3.2 Flatness

Flatness shall be in accordance with 6.4 ofBS 4965:1991, when tested using either of themethods described in annex C of BS 4965:1991.

10.3.3 Machinability of boards

Various factors such as wood type, binder content,wood density and grit content affect themachinability of boards. Good machiningcharacteristics are important requirements for boardswhich are to be edge profiled or used for veegrooving applications. A method for assessing thegrit content of boards is given in ISO 3340. Whereintensive machining operations such as profilemoulding and vee grooving are to be carried out,boards with a grit content (assessed on a sample offull board thickness) not exceeding 0.05 % should beselected or specified.

10.3.4 Surface texture

Boards to be used for laminating withresin-impregnated papers or thermoplastic foils, orfor finishing by direct painting or printing, shouldhave a finer surface texture, no large individual chipsand a higher resistance to changes in surface texturethan boards that are to be surfaced with stiffsurfacing skins such as wood veneer or plasticslaminates.

10.4 Design

10.4.1 Edge treatments

Where boards are used for applications where waterspillage is likely, for example in kitchen or bathroomfitments, all edges should be effectively sealed withadhesive bonded edging tape or otherwise treatedwith a sealant.

10.4.2 Screws and fittings

Requirements for the resistance to the axialwithdrawal of screws do not form part of thespecifications of the particleboards referred to in thisstandard; however, it is recommended that, whentested in accordance with BS EN 320, the meanresistance to axial withdrawal of wood screws fromthe face of the board shall be greater than 500 N, andgreater than 450 N from the edge.

Additional screwholding strength can be achieved byusing particle board screws or fittings whichdistribute applied loads over the widest possiblearea.

16 BSI 1998

BS 7916:1998

11 Selection and use of woodfibreboards

11.1 General

This clause gives guidance on the types and gradesof wood fibreboard which can be considered for usein various applications. The list of applicationscovers only those common uses in the constructionindustry. It is not intended that the use of thematerials is restricted solely to these applications.

The choice of fibreboard for a particular applicationwill depend on a number of factors, of whichstrength and durability will be paramount. Guidanceon the use of wood fibreboards in specificapplications can be found in the standards referredto in this clause.

Where appropriate standards are not available for aparticular application, users should refer tomanufacturer's guidance; alternatively, it may benecessary to undertake appropriate type testingand/or third party assessment to demonstratesuitability for purpose.

NOTE Until such time as the introduction of appropriateEuropean Standards, grade references given in the BritishStandards referred to in this standard will need to be substitutedwith the relevant grades listed in Tables 10 and 11. Comparativeguidance is given in annex A.

12 GradesTable 10 lists the wood fibreboard types from whichgrades for a particular application should beselected.

13 Selection of materialTable 11 gives guidance on boards which can beconsidered for use in various construction relatedapplications. It also lists those design considerationswhich may be important when selecting betweendifferent board types.

BSI 1998 17

BS 7916:1998

Table 10 Types and grades of wet and dry process wood fibreboard

Board type Grade References

Softboard

General purpose (for use in dry conditions) SB

General purpose (for use in humid conditions) SB.H

General purpose (for use in exterior conditions) SB.E BS EN 622-4

Load bearing (for use in dry conditions) SB.LS

Load bearing (for use in humid conditions) SB.HLSb

Low density medium board

General purpose (for use in dry conditions) MBL

General purpose (for use in humid conditions) MBL.H BS EN 622-3

General purpose (for use in exterior conditions) MBL.E

High density mediumboard

General purpose (for use in dry conditions) MBH

General purpose (for use in humid conditions) MBH.H

General purpose (for use in exterior conditions) MBH.E

Load bearing (for use in dry conditions) MBH.LA1 BS EN 622-3

Heavy duty load bearing (for use in dry conditions) MBH.LA2

Load bearing (for use in humid conditions) MBH.HLS1b

Heavy duty load bearing (for use in humid conditions) MBH.HLS2b

Hardboard

General purpose (for use in dry conditions) HB

General purpose (for use in humid conditions) HB.H

General purpose (for use in exterior conditions) HB.E BS EN 622-2

Load bearing (for use in dry conditions) HB.LA

Load bearing (for use in humid conditions) HB.HLA1

Heavy duty load bearing (for use in humid conditions) HB.HLA2

Medium density fibreboard (MDF)

General purpose (for use in dry conditions) MDF

General purpose (for use in humid conditions) MDF.H (option 1)a

MDF.H (option 2)a

Load bearing (for use in dry conditions) MDF.LA BS EN 622-5

Load bearing (for use in humid conditions) MDF.HLS (option 1)ab

MDF.HLS (option 2)ab

a Two options are available:

option 1 boards are suitable for interior humid conditions only;

option 2 boards are suitable for use uncoated in environments falling under biological hazard classes 1 and 2 of BS EN 335-3.

For exterior applications, only MDF.H and MDF.HLS (option 2) boards should be used. Unless the inherent and/or conferred propertiesof the board are adequate, it would be necessary to complement an option 2 board with an appropriate exterior coating system prior tousing it in a biological hazard class 3 environment (see 3.14 to 3.17).

Manufacturer's guidance should be sought on the use and protection of option 2 boards.

b These boards are restricted under humid conditions to instantaneous or short periods of loading.

18 BSI 1998

BS 7916:1998

Table 11 Guidance on the use of wood fibreboards in construction

Application Softboard Mediumboard Hardboard Mediumdensity

fibreboard(MDF)

Design consideration Applicationreferences

Architecturalmouldings

MDF - Strength and stability BS 1186-3

MDF.H - Humidity condition

MDF.LA

MDF.HLS

Box and I-beamwebs

HB.HLA2 - Strength and stability BS 5268-2

External(non-structural)a

MBL.EMBH.E

HB.E MDF.H(option 2)

- Durability- Surface finishes

MDF.HLS(option 2)

Flat roofinsulation overlay

SB.H - Durability BS 6229

SB.E

SB.HLS

Formwork lining HB.H - Durability

HB.E - Number of re-uses

HB.HLA1 - Strength and stability

HB.HLA2

Internal wallb

liningSB MBL HB MDF - Strength and stability

SB.LS MBH HB.H MDF.H - Dimensional movement

MBL.H HB.LA MDF.LA - Performance in fire

MBH.H HB.HLA1 MDF.HLS - Impact resistance

MBH.LA1 HB.HLA2 - Surface coatings

MBH.LA2

MBH.HLS1

MBH.HLS2

Movement jointfillers

SB.H - Durability DoESpecification forroad and bridgeworks

SB.E - Compression andrecovery

Overlay tostructural floors

SB: Timber floors MBH HB MDF - Strength and stability BS 8201

SB.LS MBH.H HB.H MDF.H - Wear resistance

SB.H andSB.HLS: Timberand concretefloors

MBH.LA1 HB.LA MDF.LA - Humidity condition

MBH.LA2 HB.HLA1 MDF.HLS - Surface coverings

MBH.HLS1 HB.HLA2 - Dimensional movement

MBH.HLS2

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BS 7916:1998

Table 11 Guidance on the use of wood fibreboards in construction (continued)

Application Softboard Mediumboard Hardboard Mediumdensity

fibreboard(MDF)

Design consideration Applicationreferences

Roof sarking SB.H MBL.H HB.E - Impact resistance BS 5534-1

SB.E MBL.E HB.HLA1 - Humidity condition BS 8000-6

SB.HLS HB.HLA2 - Strength and stability

- Durability

Sheathing SB.HLS MBH.HLS1 HB.HLA2 - Strength and stability BS 5268-6

MBH.HLS2 - Impact

- Vapour permeability

- Dimensional movement

Staircases MDF - Loading requirement BS 585-2

MDF.H - Humidity condition

MDF.LA

MDF.HLS

Windowboards MDF.H - Strength and stability BS 1186-3

MDF.HLS - Humidity condition

a The adequate performance of a material designated for external applications may be dependent upon the use of an appropriateexterior coating system. Manufacturer's recommendations should be followed.

b Wood fibreboards typically have a surface spread of flame rating of no greater than class 3 when tested to BS 476-7, although someboards can be post-treated or are available from the manufacturer with either a class 1 rating to BS 476-7 or a class 0 rating incompliance with the Building Regulations.

BS 7916:1998

20 BSI 1998

Table A.1 Particleboard

BS 5669-2 BS EN 312-2, -3, -4, -5, -6 and -7

Use description BS type BS EN type Use description

General purpose use (dry conditions) C1 P2 General purpose (dry conditions)

Boards for interior fitments (furniture) C1A P3 Boards for interior fitments (furniture)

Load bearing (dry conditions) C2 P4 Load bearing (dry conditions)

Moisture resistant (not load bearing) C3(M) No equivalent grade (use P5)

Load bearing (moisture resistant) C4(M) P5 Load bearing (humid conditions)

No equivalent P6 Heavy duty load bearing (dry conditions)

Heavy duty load bearing(moisture resistant)

C5 P7 Heavy duty load bearing(humid conditions)

Table A.2 Oriented strand board

BS 5669-3 BS EN 300


General purpose and boards for interiorfitments including furniture

F1 OSB/1 General purpose and boards for interiorfitments including furniture(dry conditions)

General purpose (unconditioned) F1 OSB/2 Load bearing (dry conditions)

Load bearing (humid conditions)(conditioned)

F2 OSB/3 Load bearing (humid conditions)

No equivalent OSB/4 Heavy duty load bearing(humid conditions)

Table A.3 Cement bonded particleboard

BS 5669-4 BS EN 634-2


Internal use (dry conditions) T1 No equivalent

Internal and external use T2 OPC bonded particleboard For use in dry, humid andexterior conditions

Annex A (informative)

Nearest fit comparison between BritishStandard board designations andEuropean Standard designationsTables A.1, A.2, A.3, and A.4 below are intended forguidance only, in order to assist during the period oftransition from British Standard (BS) specifications toEuropean Standard (BS EN) specifications.

The tables indicate the nearest fit comparisonbetween the grades given in BS 5669-2, -3, -4 andBS 1142 to those given in BS EN 312-2, -3, -4, -5, -6and -7, BS EN 300, BS EN 634-2 and BS EN 622-2, -3, -4and -5.

Comparisons have been made between both propertiesand also intended end uses. Since the system used tocharacterize board types is different between theBS and BS EN specifications, it should not be assumedthat the presence of a comparison for a particularboard type means that the boards have exactly thesame specification values.

BSI 1998 21

BS 7916:1998

Table A.4 Wood fibreboards

BS 1142 BS EN 622-2, -3, -4 and -5


Hardboard

Standard hardboard (dry conditions) SHB/SHC HB General purpose (dry conditions)

No equivalent (nearest match) SHA/THN HB.H General purpose (humid conditions)

No equivalent (nearest match) THN HB.E General purpose (exterior conditions)

Standard hardboard (dry conditions) THN HB Load bearing (dry conditions)

Tempered hardboard (humidconditions)

THN HB.HLA1 Load bearing (humid conditions)

Tempered hardboard (humidconditions)

THE HB.HLA2 Heavy duty load bearing (humid conditions)

Low density mediumboard

Low density mediumboard (normal) LMN MBL General purpose (dry conditions)

Low density mediumboard (extra) LME MBL.H General purpose (humid conditions)

No equivalent MBL.E General purpose (exterior conditions)

High density mediumboard

High density mediumboard (normal) HMN MBH General purpose (dry conditions)

High density mediumboard (extra) HME MBH.H General purpose (humid conditions)

No equivalent MBH.E General purpose (exterior)

No equivalent (nearest match) HME MBH.LA1 Load bearing (dry conditions)

No equivalent (nearest match) MBH.LA2 Heavy duty load bearing (dry conditions)

No equivalent (nearest match) HME MBH.HLS1 Load bearing (humid conditions)

No equivalent MBH.HLS2 Heavy duty load bearing (humid conditions)

Softboard

Softboard (normal) SBN SB General purpose (dry conditions)

Softboard (impregnated) SBI SB.H General purpose (humid conditions)

No equivalent SB.E General purpose (exterior conditions)

No equivalent SB.LS Load bearing (dry conditions)

No equivalent (nearest match)(sarking and sheathing grade)

SBS SB.HLS Load bearing (humid conditions)

Medium density fibreboard

Medium density fibreboard MDF MDF General purpose (dry conditions)

Medium density fibreboard (moistureresistant) (option 1 only)

MDFMR MDF.H General purpose (humid conditions)

No equivalent MDF.LA Load bearing (dry conditions)

No equivalent MDF.HLS Load bearing (humid conditions)

22 BSI 1998

BS 7916:1998

Annex B (informative)

Determination of punching shear(concentrated load)

B.1 Principle

A load is applied to the surface of a rigidly supportedtest specimen, via a punch (loading head) of specifiedarea, until the maximum applied load is obtained.

B.2 Apparatus

B.2.1 Punching shear test rig, as shown in Figure B.1.The test rig should be capable of applying sufficientload to cause the test specimen to fail and should befitted with appropriate circular punch sizes. It shouldbe capable of testing all the common thicknesses ofboards and of encompassing punch sizes of 25 mmto 200 mm in diameter. It should have a steelsupporting plate and a clamping device. The steelsupporting plate shall have a thickness of Lmin/20,where Lmin is the minimum side length of the testspecimen (see B.3), and a circular aperture at itscentre with a diameter, D, rounded to thenearest 10 mm, of:

D = 6T + d + 25

where

T is the board thickness in millimetres;

d is the punch size in millimetres.

The supporting frame should be rigid.

B.2.2 Adequate ancillary equipment to measure allthe necessary loads and deformations and to recordand store all the test data continuously during eachtest. Where the accuracy of the equipment is specified,the equipment should be periodically calibrated.

B.3 Test specimens

Test specimens should be square with a minimum sidelength Lmin, in millimetres, of:

Lmin = D + 75

where

D is the diameter of the circular aperture of thesupporting plate in millimetres.

Test specimens should be conditioned to constantmass at (20 2) C and (85 5) % r.h. Constant mass isconsidered to have been achieved when the results oftwo successive weighing operations, carried out at aninterval of 24 h, do not differ by more than 0.1 % of themass of the test specimens.

B.4 Procedure

Mark the diagonals on one face of the test specimen.

Measure the thickness at a point on eachdiagonal 25 mm from each corner, to thenearest 0.1 mm, using a micrometer.

Calculate the test specimen thickness to thenearest 0.1 mm from the mean of the four values.

Place the test specimen in the support fixture asshown in Figure B.1. Rigidly clamp the test specimenso that no uplift occurs at the board edges whenloaded.

Position the complete assembly in the testing machineso that the centre of the punch is directly over theintersection of the diagonal marks.

Apply a continuously increasing load to the testspecimen until the maximum applied load is attained.The movement of the punching head shall becontrolled by a constant rate of loading such that themaximum applied load is obtained after 300 s 120 s.

B.5 Results and analysis

The test results should be expressed to thenearest 0.1 N.

The following should be obtained:

the mean ultimate punching shear load W (in N);

failure diameter and actual failure plane area.

BSI 1998 23

BS 7916:1998

a) Test rig

b) Support plate

All dimensions are in millimetres

Figure B.1 Layout of punching shear test rig

24 BSI 1998

BS 7916:1998

Bibliography

Standards publications

BS 476-7:1997, Fire tests on building materials and structures Method of test to determine the classificationof the surface spread of flame of products.

BS 585-2:1985, Wood stairs Specification for performance requirements for domestic stairs constructed ofwood based materials.

BS 1142:1989, Specification for fibre building boards.

BS 1186-3:1990, Timber for and workmanship in joinery Specification for wood trim and its fixing.

BS 4875-7:1985, Strength and stability of furniture Methods for determination of strength of storagefurniture.

BS 4875-8:1985, Strength and stability of furniture Methods for determination of stability of storagefurniture.

BS 4965:1991, Specification for decorative laminated plastics sheet veneered boards and panels.

BS 5250:1989, Code of practice for control of condensation in building.

BS 5268-2:1996, Structural use of timber Code of practice for permissible stress design, materials andworkmanship.

BS 5268-6.1:1996, Structural use of timber Code of practice for timber frame walls Dwellings notexceeding four storeys.

BS 5534-1:1997, Code of practice for slating and tiling Design.

BS 5589:1989, Code of practice for preservation of timber.

BS 5669-1:1989, Particleboards Methods of sampling, conditioning and test.

BS 6229:1982, Code of practice for flat roofs with continuously supported coverings.

BS 6399-1:1996, Loading for buildings Code of practice for dead and imposed loads.

BS 8000-6:1990, Workmanship on building sites Code of practice for slating and tiling of roofs andcladdings.

BS 8201:1987, Code of practice for flooring of timber, timber products and wood-based panel products.

BS 8204-1:1987, Screeds, bases and in situ floorings Code of practice for concrete bases and screeds to receivein situ flooring.

BS EN 204:1991, Classification of non-structural adhesives for joining wood and derived timber products.

BS EN 300:1997, Oriented strand boards (OSB) Definitions, classifications and specifications.

BS EN 309:1992, Wood particleboard Definition and classification.

BS EN 312-1:1997, Particleboards Specifications General requirements for all board types.

BS EN 312-2:1997, Particleboards Specifications Requirements for general purpose boards for use in dryconditions.

BS EN 312-3:1997, Particleboards Specifications Requirements for boards for interior fitments (includingfurniture) for use in dry conditions.

BS EN 312-4:1997, Particleboards Specifications Requirements for load-bearing boards for use in dryconditions.

BS EN 312-5:1997, Particleboards Specifications Requirements for load-bearing boards for use in humidconditions.

BS EN 312-6:1997, Particleboards Specifications Requirements for heavy duty load-bearing boards for usein dry conditions.

BS EN 312-7:1997, Particleboards Specifications Requirements for heavy duty load-bearing boards for usein humid conditions.

BS EN 316:1993, Wood fibreboards Definitions, classification and symbols.

BS EN 320:1993, Fibreboards Determination of resistance to axial withdrawal of screws.

BS 7916:1998

11) Obtainable from Schall Property Services (Publications group), 3rd floor, The Lansdowne Building, Lansdowne Road, Croydon, SurreyCRO 2BX.

12) Obtainable from The Stationery Office, 49 High Holborn, London WC1V 6HB.

BS EN 335-1:1992, Hazard classes of wood and wood based products against biological attack Classificationand hazard classes.

BS EN 335-3:1996, Hazard classes of wood and wood based products against biological attack Application towood-based panels.

BS EN 622-1:1997, Fibreboards Specifications General requirements.

BS EN 622-2:1997, Fibreboards Specifications Requirements for hardboards.

BS EN 622-3:1997, Fibreboards Specifications Requirements for medium boards.

BS EN 622-4:1997, Fibreboards Specifications Requirements for softboards.

BS EN 622-5:1997, Fibreboards Specifications Requirements for dry process boards (MDF).

BS EN 633:1994, Cement-bonded particleboards Definition and classification.

BS EN 634-1:1995, Cement-bonded particleboards Specifications General requirements.

BS EN 634-2:1997, Cement-bonded particleboards Specifications Requirements for OPC bondedparticleboards for use in dry, humid and exterior conditions.

BS EN 1128:1996, Cement-bonded particleboards Determination of hard body impact resistance.

DD ENV 1995-1-1:1994, Eurocode 5 Design of timber structures General rules and rules for buildings.

prEN 12369, Wood-based panels Characteristic values for established products.

prEN 1195, Timber structures The testing of structural floor decking.

prEN 12869-2, Wood based panels Structural floor decking on joists Part 2 Performance requirements.

ISO 3340, Fibre building boards Determination of sand content.

Other documents

[1] The Control of Substances Hazardous to Health Regulations (COSHH) 1994, published by The StationeryOffice, London.

[2] Platform floors: technical guidance. PSA MOB 01-707, published by the Property Services Agency, 198111).

[3] Specification for road and bridge works, published by the Department of the Environment12).

BSI389 Chiswick High RoadLondonW4 4AL

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