Most new constructions today utilize roof trusses rather than the traditional roofing support systems of the past. Pre-fabricated trusses are an economical alternative to hand-framing and are easier to install. Even with a pre-fabricated truss system, however, there are always some modifications to be made on-site.
Roof trusses must be ordered at least 2 to 3 weeks before work is scheduled to commence. Trusses are manufactured according to exact specifications based on the building’s blueprints. Roof trusses may be ordered through local lumberyards or home improvement stores.
Once walls are in place, roof trusses can be installed. It is wise to mark each cap plate to indicate where the truss heels will land. Typically secured on 24-inch centers, it is important to measure carefully when marking the caps. For gable roofs, 2 gable end trusses will be included which utilize more vertical members than the other trusses do. This is done in order to support the gable end sheathing. At the point where you started your measurements, raise one of the gable ends into place, making certain that it is flush with the edge of the cap plate and nail it securely. At this point, the roof trusses can be lifted into place. This may be accomplished by hand or by the use of a crane. Using a crane is more expensive but easier, and either method is suitable. If raising and positioning by hand, the following steps should be taken:
Set one end on a wall plate with the truss turned upside down. Place the other end on the other wall plate. Swing the truss so it sits upright. Rest it against the secured gable end truss.
Repeat this process, one at a time, and stack trusses against the gable end truss, being certain that the other gable end truss is the last one to go into place.
Hand raising trusses can be accomplished with only two people, but ideally, several more workers will make the process easier.
Once the roof trusses are stacked into a place they can be positioned one at a time. Begin with the second gable end truss, and work back towards the first gable end. Bracing the second gable end is advisable. This is done by plumbing the truss and securing as described above for the first gable end. The remainder of the trusses should be braced with 1x4s. Using the same 24-inch on-center measurements that you marked on the wall plates earlier, mark each truss for bracing. When several trusses are in place, nail the end of the brace over the second gable end truss. Then nail the brace securely to the other trusses. Each brace should correspond to the marks made previously. This ensures proper spacing and assures that the trusses are plumb.
If the second gable end truss is not exactly 24-inches on center, which is frequently the case, the brace position must be modified. Measure the distance between the trusses along with the cap plate and divide in half exactly, marking the halfway mark. Move the end of the brace as much as necessary to match up to the new roof trusses mark.