How to Install an Attic Truss

Employ a crane to lift attic trusses, which typically are too large to be raised from the ground. Lift trusses up to 44 feet wide by installing lifting ropes on the top or rafter chords about midway between the peak and the outer edge; in many attic trusses, this will be at the inside vertical brace. As an alternative, nail a board horizontally across the rafter chords and put lifting ropes on that. Install a guide rope on the bottom truss chord in either case.

Raise the truss with the crane to the proper location. Use the guide rope from the ground to steer it into position for roof workers to set. Have braces ready -- boards to connect the truss to stakes in the ground outside the wall. Set the truss into place and have workers on the roof secure it to the braces and to the wall caps with 16d framing nails and a hammer. Drive two nails on one side of the truss, one on the other on each wall cap.

Work from the back of the house forward but move trusses from front to back. Install lateral bracing across the trusses starting with the third one. Nail braces horizontally across truss bottom chords and temporarily across the outside of each rafter. Check each truss with a level to be sure it is plumb vertically and make certain the back edge of each truss chord is exactly on the marked line.

Brace the trusses permanently according to a house plan, typically by installing diagonal braces from the top of one truss to the bottom of the third one down; the style and number of these braces will vary with the length of the roof. Nail permanent lateral braces across to tops of bottom chords outside the attic room area.

Add hurricane clips on the end of each truss chord where it meets the wall cap. Nail these metal brackets to the wall caps and to the truss chords with 8d galvanized nails to tie the trusses more firmly in place. Put a tie on each truss chord. Reinforce this bracing if desired by installing truss ties, similar to hurricane ties, on any interior wall on which a truss bottom chord rests. Secure these with nails or galvanized screws driven with a screw gun.