How Do You Build Trusses?


Quick Answer

To build trusses, determine the pitch, or the slope, of the roof, and use a rafter square to measure the angles needed to construct the trusses with the correct slope. Make the mitered cut on each rafter, and secure them to the ceiling joist.

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Full Answer

  1. Measure and cut the wood

    A truss is comprised of three main parts: two rafters and a ceiling joist. The ceiling joist is the width of the house. Use an online calculator to find the length of the rafters, which is determined by the pitch of the roof, amount of overhang and the width of the ceiling. Use a rafters square to cut 2-by-4 boards at the correct angles. If the pitch is 7:12 (a vertical gain of 7 inches for every horizontal foot), use the No. 7 notch to align the cuts. For the center cut, align the No. 7 along the edge of the board, and mark the cut on the right-edge side of the square. For the end cuts, align the fence of the square with the edge of the board, and mark the cut at the No. 7 notch.

  2. Build the trusses

    Lay out the two rafters and the joist. On both sides of each joint, attach plywood scraps with adhesive and 1 1/2-inch roofing nails. On gable-end trusses, do not add the gussets on the side that faces out, since siding is added on this side.

  3. Install the trusses

    Rest a truss on the top plate of the outer walls. Starting at one end, flip the trusses up into place, and secure with 3 1/2-inch roofing nails. Continue adding trusses until you reach the other end of the roof.

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