How to Set Roof Trusses

A roof truss is a structural framework designed to provide support for a roof without installing centre supports. Trusses are structurally engineered and are manufactured by licensed truss companies, but people also make trusses for their roofs. Home builders nowadays prefer structurally engineered roof trusses over traditional stick framed roofs which were supported by coupled rafters because they are quick to install. Moreover, the former also do not require complicated roof angles. Installing roof trusses is no doubt very simple as compared to traditional framing, but there is less room for error and you need to be very careful.

Read and understand the diagram and layout

Roof trusses are manufactured by licensed companies and arrive the jobsite with a stamped copy of plans and a diagram and layout of the truss configuration. Thoroughly read and understand the instruction sheet before transferring the numbers on the trusses to the top wall plates. Since the truss members are heavy and a crane is required to move them, it is necessary to understand their numbering before you start moving them to the top wall plates.

Setting the First Trusses

The manufacturer’s guide clearly explains every step involved in truss installation, so it is very important to consult the guide before moving on to next step. Most of the trusses will be set on the side of the roof opposite to the location of the truss numbered one. It is better to move the first truss manually to the end of the roof. Stand the truss up, position it on the corresponding number and nail to the wall plate on both sides. Also attach a temporary braces to hold the truss in an upright position.

Setting Subsequent Trusses

Set the second truss following the above mentioned instructions and attach a ridge beam to the peak of both trusses. The beam should be extending to the far end of the roof, hanging over the trusses that are yet to set. Now position the remaining trusses one by one, attaching each truss to the wall plates and to the ridge beam.

Truss Attachment

Roof trusses are designed to work as a single unit to ensure the structural integrity of the roof remains intact. But changes in temperatures and humidity levels can stress the truss members, causing the centre of the bottom chord lift upward. This only happens when the bottom chord is nailed to the top of the undesignated interior walls. Never nail the truss members at your own will, instead nail them only where specified by the manufacturer.