BS 5268-3:1998

Committees responsible
Foreword
Introduction
1 Scope
2 Normative references
3 Terms, definitions and symbols
4 Assessment of structural adequacy
5 Materials
    5.1 Timber
    5.2 Plywood
    5.3 Fasteners
    5.4 Adhesives
    5.5 Preservative treatment
6 Trussed rafter design
    6.1 General
    6.2 Limitations
    6.3 Permissible stresses, fastener loads and nail
         spacing
    6.4 Loads
    6.5 Method of design
7 Roof design
    7.1 Design responsibilities
    7.2 Overall stability
    7.3 Wall plates
    7.4 Plasterboard ceilings
    7.5 Water tanks
    7.6 Hatch, chimney and other openings
    7.7 Roof environment
8 Fabrication
    8.1 General
    8.2 Assembly
    8.3 Marking
9 Handling, storage and erection
    9.1 Handling and transportation
    9.2 Storage
    9.3 Erection
    9.4 Modification and repairs
10 Load testing
    10.1 General
    10.2 Testing authority
    10.3 Information required by the testing authority
    10.4 Quality and fabrication of trussed rafters for
         test
    10.5 Tests on similar configurations
    10.6 Acceptance
    10.7 Use of tested trussed rafters
11 Exchange of information
    11.1 Information required by the trussed rafter
         designer
         from the building designer
    11.2 Information to be provided by the trussed rafter
         designer to the building designer
Annex A (normative) - Standard roof bracing
Annex B (normative) - Permissible spans
Bibliography
Figures
1 Alternative trussed rafter models for structural
   analysis
2 Examples of joints
3 Wall plate location for simplified analysis
4 Shear stress condition at joints
5 Tension stress condition perpendicular to grain at
   joints
6 Truss deflection components
7 Supports for water tanks
8 Spacing of trussed rafters to accommodate openings
9 Chimney opening
10 Hatch opening
11 Trusses rafter specification
A.1 Standard bracing for rafter and web members of
    duopitch trussed rafters
A.2 Standard bracing for rafter and web members of
    monopitch trussed rafters
A.3 Limiting spans for standard bracing of trussed
    rafter roofs
A.4 Basic wind zones
A.5 Procedure for determining bracing design requirements
B.1 Truncated Fink trussed rafters
Tables
1 Species of timber
2 Modification factors for finger joint efficiency ranges
3 Maximum bay length of chord members
4 Maximum length of internal members
5 Minimum nail spacing for metal to timber joints
6 Summary of rafter loads
7 Summary of ceiling tie loads
8 Example load combinations
9 Bending moment coefficients (Km)
10 Load-sharing factors for principle trussed rafters
11 Force modification factor (Ke) for joints in
   eccentrically loaded components subject to tension
   perpendicular to grain
12 Modification factor (Kt) for strength tests on trussed
   rafters
A.1 Thickness and fixing of sarking materials
B.1 Maximum permissible spans for rafter members shown
    in Figure 11
B.2 Maximum permissible spans for ceiling ties shown in
    Figure 11

Provides guidance on the design, fabrication, use, handling, storage, erection and bracing of trussed rafters. Annex gives permissible spans for two common truss configurations.