Widely used for a range of building types, trussed rafters are an economical, versatile and straightforward solution to providing a roof over a building.
Trussed rafters are individually designed prefabricated structural components made from strength-graded timber members of the same thickness, joined together with punched metal plate connectors. Available as a proprietary product from various suppliers, trussed rafter components are manufactured to design code standards. They can be used to provide a structural framework to support a building's roof fabric, room ceilings and floors.
This Wood Information Sheet focuses on how to design for and install trussed rafter products and is intended for architects, engineers and builders using trussed rafter components. It is an overview of the subject with signposts to more detailed sources that are listed at the end.
- Room in the Roof (RIR or attic) trussed rafters
- Standards and quality control
- Trussed rafter design
- Roof design
- Handling, storage and installation
This WIS was updated in December 2020 with minor amendments, including the removal of references to BS 5268, now withdrawn by the BSI.
There are a number of ways to design and construct pitched roofs using timber. Traditionally, builders constructed them on site, cutting and fitting each piece to its neighbours. Following the Second World War, various forms of prefabricated truss were developed, with the intermediate rafters and purlins cut and fitted on...
This information sheet is an extrapolation of the standard bracing requirements given in BS 5268-3 extended to cover 'Room in the Roof' trussed rafters. All the information given here should be read in conjunction with the requirements of that standard.
- Why brace trussed rafter roofs?
- Bracing responsibility ...
Trussed rafters must be braced to create a rigid and stable roof structure. If the bracing is omitted, wrongly positioned or badly fixed, it may result in distortion or failure of individual trusses or in some instances the whole roof.
This information sheet gives a summary of the standard...