Roof trusses are the skeleton of your roof. They come in several styles and sizes, and each truss is custom built and delivered to your work site. So how do you install them once they arrive? In most cases, you won't need a special installation crew for roof trusses. Do-it-yourself home builders can usually install trusses up to 30 feet in length with minimal assistance.
Measure out and mark the placement of each truss on the exterior walls according to the building design and manufacturer recommendations for your trusses. Spacing of each truss and of temporary restraints will depend on the truss span (length). The Structural Building Components Association (SBCA) publishes a collection of PDF charts and diagrams to calculate this spacing (see Resources).
Set ground bracing. The first truss must be braced to the ground for stability. Ground bracing can be interior (within the structure) or exterior (on the ground outside). The SBCA recommends interior ground bracing if the ground outside the building is not level.
Hoist each truss into position. It's easiest to use a crane or rigging and hoisting equipment to set trusses, but two or more people can lift and set trusses up to 9 m (30 feet). Stand on scaffolding to safely slide each truss into its marked position.
Brace the trusses. Nail temporary lateral and diagonal bracing to each truss once it's hoisted into position to give the trusses stability and prevent a domino effect if there's a strong wind or one of the trusses tips during installation. Place bracing according to the manufacturer's recommendations.
To hoist a single truss by hand -- if it's less than 9 m (30 feet) across, turn the truss upside down and place one corner at a time up onto the walls. Carefully slide the truss into place and use a long 5 x 10 cm (2 x 4 inch) board to lift the truss right side up. A second (or third) person will need to stand on the scaffolding to help raise the truss and hold it steady.
Do not self-install trusses longer than 18 m (60 feet). A professional bracing system designed by an engineer must be used on trusses that size. Use extreme caution when installing trusses. The SBCA reports that incorrect truss handling and improper bracing are the leading causes of injury on building sites.