How to Engineer a Truss

Compute the span by measuring the distance between the two walls with a measuring tape. Each end of the truss rest on a wall section. Use straight 2-by-4-inch planks to make the trusses. Cut two lengths of lumber the same length as the measurement for the span. These components serve as the top and bottom chords that make up the truss. Besides providing a wide surface for nailing and applying construction adhesive, the width of the chords makes for a quiet floor.

Put the two planks together on the narrow edges on top of a work bench. Using a measuring tape, start from one end and mark off every 16 inches on the planks. Use a framing square to mark off ¾-inches on each side of the 16-inch marks. These marks guide the placement for the 2-by-4-inch vertical braces installed between the chords.

Cut 9 1/4-inch-long vertical braces for the truss. Base the number of braces on the number of 16-inch vertical lines marked on the chords, and add two for the corner braces. Install the two end braces. Use a drill and bit with a diameter slightly smaller than a 16-penny nail to pre-drill the nail holes. Position the braces between the ¾-inch marks made on the chords and secure in place.

Build the truss web, which consist of the diagonal components that fit between the braces. Use a miter saw to make a 30-degree angle cut on an 8-foot long, 2-by-4-inch-long plank. Lay the mitered end of the plank against the first brace from the end of the truss where it connects to bottom chord. Place the other end of the plank against the inside corner of the top chord and corner brace, and make a mark. Make a 30-degree angle cut on this mark.

Repeat the process to create the rest of the diagonal braces. Add metal truss plates, which provide more reinforcement for the joints between vertical braces and the top and bottom chords. Place the metal truss plates on every joint on both sides of the truss.