BS 8103-3:2009 - Structural design of low-rise buildings. Code of practice for timber floors and roofs for housing – BSI British Standards

BS 8103-3:2009

Structural design of low-rise buildings. Code of practice for timber floors and roofs for housing

Status : Current, Under review   Published : November 2009



BS 8103-3:2009 Structural design of low-rise buildings. Code of practice for timber floors and roofs for housing

BS 8103-3 gives recommendations for the sizes of timber elements, fixings, and their connections with masonry walls, floors and roofs.

BS 8103-3 applies to:

  • Detached houses
  • Semi-detached houses
  • Terraced houses
  • Flats (with not more than four self-contained dwelling units per floor, accessible from one staircase)
  • Single-storey non-residential buildings e.g. domestic garages and annexes, not exceeding 36 m2 in floor area

BS 8103-3 is of use for property of not more than three storeys above ground, intended for domestic occupation.

The design of proprietary housing systems, i.e. cross wall constructions, timber framed houses, steel or concrete framed constructions, concrete panel constructions, is not covered by this standard.

The recommendations of BS 8103-3 apply only to housing where:

a) The construction comprises masonry walls, timber roofs, suspended timber or precast concrete intermediate floors, suspended timber or concrete ground floors (either suspended or ground bearing)
b) The roof profile is symmetrical duopitch, monopitch or flat
c) The maximum clear span of a pitched roof does not exceed 12.0 m and imposes a total load on the supporting perimeter walls not greater than 12 kN/m run
d) Gable and separating walls are of masonry construction extending up to the roof line in the case of pitched roofs
e) The roof area is not larger than 200 m2 on plan, or, in the case of pitched roofs where no parapets exist, one of the roof dimensions does not exceed 10 m
f) There are no other buildings within 1.5 m of the perimeter of the building
g) The roof has no abrupt changes of height greater than 1 m on which snow drifting could occur
h) The maximum clear span of any floor joist or flat roof joist does not exceed 6.0 m
i) The design wind criteria is within the scope of BS 8103
j) No part of any wall or roof is higher than 15m above the lowest adjacent ground level
k) Floor joists, ceiling joists, flat roof joists, common or jack rafters or trussed rafters are spaced at centres which do not exceed 600 mm
l) The stability requirements and dimensional limitations accord with BS 8103-1:1995+Amendment 1:1995, Clause 5.

BS 8103-3:2009 replaces BS 8103-3:1996, which is withdrawn.

Contents of BS 8103-3:
Normative references
Terms and definitions
Spans, sizes and spacings for solid timber members, notching, drilling and end-trimming
Trussed rafter pitched roofs
Flat roof decking of timber, plywood, particleboard or OSB
Transportation, storage and handling
Assembly and erection
Durability of materials
Annex A (normative) Maximum recommended moisture content at time of erection or fixing
Annex B (normative) Species and grading rules for softwood flooring and flat roof decking
Annex C (normative) Identification marks for strength-graded timber
Annex D (normative) Species and grading rules for battens for slating and tiling
Annex E (normative) Plywood types and grades
Annex F (normative) Identification marks for plywood
Annex G (normative) Identification marks for particleboard
Annex H (normative) Identification marks for Oriented Strand Board (OSB)
Annex I (normative) Fixing of flooring
Annex J (normative) Fixing of flat roof decking
Annex K (informative) Fixing of battens for roof slating and tiling
Annex L (informative) Typical floor and flat roof constructions and their self weight, and self weight of slates and tiles for pitched roof construction
Annex M (informative) Simplified guidance on the imposed snow loading which is relevant for a particular site
Annex N (informative) Roof bracing recommendations for small single-storey non-residential buildings and annexes with pitched roofs, within the scope of Annex A of BS 8103-2:2005
List of figures
List of tables

See more timber standards


Standard NumberBS 8103-3:2009
TitleStructural design of low-rise buildings. Code of practice for timber floors and roofs for housing
StatusCurrent, Under review
Publication Date30 November 2009
Confirm Date18 February 2020
Normative References(Required to achieve compliance to this standard)BS EN 14081-1:2005, EN 15228, BS 8103-1, BS 5628-3, BS 8103-2, BS 6100-3, BS 5534, BS EN 1912, BS EN 300, BS 1210, BS EN 312, BS EN 13556, BS EN 912, BS 5268-3, BS 1202-1, BS EN 350-2, BS EN 845-1, BS EN 636, BS EN 338, BS 8417:2003, BS 1297, BS EN ISO 3166-1, BS EN 336, BS 4320, BS 4978, BS EN 13986, BS EN 335-1, BS EN 1991-1-1, BS EN 1991-1-3, BS 4190
Informative References(Provided for Information)BS 8217, NGRDL:1975, Control of Pesticides Regulations 1986, BS 8103-2:2005, 89/106/EEC, BS 5268-7.4, NBS PS 20-70, BS 5268-7.1, BS EN 1991-1-4, BS 8103-1:1995/AMD 1:1995, Building Regulations 2000, BS 5268-2, NGRDL SPS2:2003, Building Regulations (Northern Ireland) 2000, BS EN 204, CSA 0141-1970, BS 5268-7.3, BS 5268-7.2, BS 8747, BS EN 1995-1-1, Building (Scotland) Regulations 2004
ReplacesBS 8103-3:1996
Draft Superseded By08/30140202 DC
DescriptorsBattens, Pitched roofs, Structural design, Housing, Fasteners, Marking, Roof decking, Bracings, Purlins, Beams, Grades (quality), Imposed loading, Roof trusses, Size, Wood, Erecting (construction operation), Fixing, Spaced, Joists, Design, Floors, Structural timber, Roofs, Rafters, Flat roofs
Title in FrenchConception structurale de batiments a bas niveau. Code de bonne pratique de parquets et toits en bois pour encastrement
Title in GermanStrukturgestaltung von niedrigen Gebaeuden. Anleitung fuer die Praxis der Holzfussboden und Holzdaecher fuer Wohnhaeuser
ISBN978 0 580 55897 9
File Size29.79 MB

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