BS 5268-3:1985

Foreword
Committees responsible
Code of practice
Section one. General
0 Introduction
1 Scope
2 Definitions and symbols
3 Assessment of structural adequacy
Section two. Materials
4 Timber
5 Plywood
6 Fasteners
7 Adhesives
Section three. Functional requirements
8 Environment
9 Loading
10 Deflection
11 Preservative treatment
Section four. Design of trussed rafters
12 General
13 Limitations
14 Permissible stresses, fastener loads and nail
    spacings
15 Loads
16 Method of design
Section five. Design of trussed rafter roofs
17 Design criteria
18 Compression buckling
19 Overall roof stability
20 Wall plates
Section six. Fabrication
21 General
22 Moisture content
23 Assembly
24 End joints
25 Camber
26 Marking
27 Inspection
Section seven. Handling, storage and erection
28 Handling and transportation
29 Storage
30 Erection
31 Modification and repairs
Section eight. Load testing
32 General
33 Testing authority
34 Information required by the testing authority
35 Quality and fabrication of trussed rafters for test
36 Testing equipment
37 Test conditions
38 Test procedure
39 Acceptance
40 Test report
41 Use of tested trussed rafters
Section nine. Permissible spans
42 General
43 Internal members
44 Span limitations
45 Modification to Fink configurations
Section ten. Information required
46 Designer, fabricator and client
Appendices
A Standard bracing for domestic roofs
B Erection
Tables
1 Species of timber
2 Modification factors for finger joint efficiency
    ratings
3 Minimum ventilation openings
4 Maximum bay length of rafters and ceiling ties
5 Maximum length of internal members
6 Minimum nail spacing for metal to timber joints
7 Summary of rafter loads
8 Summary of ceiling tie loads
9 Bending moment coefficients (Km)
10 Load-sharing factors for principal trussed rafters
11 Maximum deviation from vertical
12 Modification factors for test on similar trussed
    rafters
13 Maximum permissible spans for rafter members shown
    in figure 6
14 Maximum permissible spans for ceiling ties shown in
    figure 6
Figures
1 Examples of common joints
2 Supports for water tanks
3 Spacing of trussed rafters to accommodate openings
4 Chimney opening
5 Hatch opening
6 Common trussed rafter configurations
7 Location of wall plate
8 Truncated Fink trussed rafters
9 Limits of basic wind speed zones
10 Limits of standard bracing for trussed rafters
11 Standard bracing for rafter members and web members
    of duopitch trussed rafters
12 Standard bracing for rafter members and web members
    of monopitch trussed rafters
13 Method of erection for domestic roofs
14 Procedure for determining bracing design
    requirements
Index

Gives guidance on the design, fabrication and use of trussed rafters for pitched roofs. Intended primarily for dwellings, it is applicable also to other buildings where the environment or service conditions are similar. It recommends maximum spans for a range of member sizes and roof pitches for two common configurations of monopitched and duopitched roofs. These spans may be used under specific conditions without further calculation or proof testing. Design guidance is given for these and other configurations with consideration of bracing requirements and overall roof design.