Trusses. You literally would not have a roof
over your head without them. An essential element to any home, trusses not only support your ceiling, they offer architectural interest inside and allow for the open expanse of your great room — whether your timber frame is reminiscent of a grand cathedral or as cozy
as a cottage.
Unlike most modern stick-built homes, timber-framed trusses are frequently exposed, amplifying the feeling of space and volume inside. The timber frame ceiling can be at the roofline rather than tied to the base of the truss’s lower beam, and individual rooms can have varying ceiling heights thanks to that flexibility. However, the newfound ceiling height and architectural interest of a timber truss often mean an engineer is required to guarantee these beautiful open trusses will hold up under the load of the roof.
According to the Timber Framers Guild
, (a non-profit membership organization dedicated to the art and science of timber framing), to determine the span and scale of a timber truss, a structural engineer follows these four steps:
- Identify and quantify the loads of the structure, according to the International Residential Building Code (in the U.S.)
- Select the member sizes and materials for the timber frame
- Examine how the building will behave under the load
- Refine materials and member sizes to achieve effective performance
and engineered to meet the criteria above, the trusses are pre-cut in the timber framer’s shop. They may be assembled there or onsite, depending on the timber framer and the site’s restrictions. Modern timber frame trusses can be connected using exposed steel plates and brackets or the traditional mortise-and-tenon method, using wood pegs to secure the pieces together instead of metal fasteners or nails.
There are five basic modern trusses: common, queen post, king post, hammerbeam and scissor.
Check Out These Timber Frame Trusses:
The Common Truss is, as its name implies, the truss most often seen in modern timber frames, and is both strong and affordable. It’s a clean design, easily identified by the manner in which the lower horizontal beam (chord) joins the two rafters.