A review of timber frame roof systems

There are a diverse number of roofing systems available today. These range from the traditional cut-roof of rafters carrying slates, to laminated arched purlins supporting interlocking prefabricated roof panels.  Here we look at three broad types of roof system; timber framing, engineered solutions and truss systems.

The timber framed roof system can be spit into two types:  stick framing or the cut-roof and timber framing.  Both share common roots involving traditional methods, practices and principals of triangulating forces.  Both method use solid-timber stock and require skilled labour to assemble the roof framework.

With stick framing the timber is delivered to site in standard lengths and hand-cut in situe to form a roof framework. Whilst the raw material costs are relatively low, the process of assembling the roof framework requires the time and costs of skilled labour. Cut-timber framing of domestic dwellings has evolved to be as cost effective as possible, using braces and hangers to reduce timber sections.

The second type of timber framing, involves assembling timbers to construct a self-supporting frame or truss. The frame could be made using traditional joinery methods, for example mortice and tenons or more modern bolts and plates.  The trusses can be designed to sit on load bearing walls and carry the loads from cut-timber infill or purlins and panels.  In post and beam construction, the framework could one of many forming the structure of the entire house and incorporating not only rafters but beams to carry floor loads. Modern engineering allows the manufacture of large section green oak frames to the tolerances of furniture.

Extract from: A comparative review of timber frame roof systems