How to Install Prefabricated Trusses

Planning for Installation

• 1

  Closely examine the home's blueprints or building plans. Many homes have a number of roof planes, and each area will have a separate type of truss. When the trusses arrive, they will be labeled, but packaged together in a single bundle. By studying the plans, you will be familiar with the installation process and able to stack the trusses in the proper order for installation.

• 2

  Lay out the truss locations along the top plate of all the home's exterior walls. The trusses are installed either 16 or 24 inches apart from one another. Before the trusses arrive, mark the location of the trusses on the walls, so they are installed in the correctly corresponding location.

• 3

  Gather the 2-by-4-inch dimension lumber to use in framing the gable ends and tacking the trusses together during the installation process. As each truss is installed, it is tacked to the first so that the trusses don't fall before they are connected into a single, integrated roof system.

Installing the Trusses

• 4

  Sort the trusses after delivery by the order in which they will be installed. Set the trusses in piles around the construction site, with the first truss on top of the pile, and the trusses below stacked in the order in which they are to be lifted onto the house. Install one of the gable trusses at the end of the roof first. Hold this truss in place by running multiple pieces of 2-by-4 dimension lumber down to the ground level. These pieces of framing are removed after the rest of the roof is framed in.

• 5

  Install the trusses across the largest single length of the home first. Each truss must be level, plumb and square to the frame of the house. Use 2-by-4-inch dimension lumber nailed across the trusses to tack them into place as they are installed. Toenail the trusses to the exterior wall plate perfectly centered on your layout markings. Install the trusses for any reverse gables, or smaller roof planes, after the largest area of the roof is framed. Follow the same procedure for the smaller trusses that you followed for the larger trusses.

• 6

  Complete the roof framing by hand in the valleys of the roof system where two different roof planes meet. Frame these areas in, where roof planes intersect, with 2-by-6-inch and 2-by-8-inch dimension lumber. These single joists should be 16 inches apart and parallel to the existing trusses.

• 7

  After the trusses are installed, lay and nail the 1/2-inch OSB roof decking across the roof deck surfaces. Use the OSB to pull the trusses into alignment. The result will be a completely new roof installed over the existing roof.

• 8

  While the roof decking is being installed, use the rafter ties to nail the trusses to the top plate on the exterior walls around the building. Make sure to check with local building codes and use the proper size, gauge and quantity of rafter ties. These simple metal connectors strengthen the joint between the roof system and the walls to prevent catastrophic failure during severe storms.