A truss joist refers to the framing component used to provide support for flooring systems in residential, commercial, institutional and agricultural buildings. Each end of a truss rests on a wall section. The truss must incorporate certain elements of design to ensure the component has the strength to support the necessary load or weight. The parallel chord truss is the most common design used for floor joists.
Things You'll Need
16 penny nails
Measure the span for the trusses. The span represents the distance between the two wall sections that support each end of the joists. Place 2-by-4-inch boards on the worktable. Measure the span on both boards and cut to the desired length. These are the top and bottom chords for the truss. This design allows for a wide nailing surface and adhesives, which ensure a quiet floor.
Place the two boards together, upright, on the narrow edge. Use the carpenter's pencil to make marks along the edges every 16 inches. Place marks on each side of the 16-inch marks spaced 3/4 inch. Position a straight edge or framing square on each 3/4-inch mark. Draw a vertical line down the edges of the 2-by-4-inch material. This line guides the positioning of the vertical braces required between the two 2-by-4-inch truss components.
Count the number of vertical lines and add 2. Cut this number of 9 1/4-inch pieces from 2-by-4-inch material. Place a 9 1/4-inch brace between the ends. Connect the two ends of the chords. Pre-drill two holes through each of the top and bottom chords and into the 9 1/4-inch end blocks. Use 16 penny nails to secure the chords to the blocks. Place the other 9 1/4-inch blocks on the remaining 16-inch vertical lines. Pre-drill the holes and nail the components in place.
Construct the web of the truss. Position the miter saw at a 30-degree angle, or adjust the angle according to the desired web opening. Make a 30-degree cut on an 8-foot-long, 2-by-4-inch board. Position the mitered end of the board against the first 9 1/4-inch lateral brace where it joins the bottom chord.
Angle the board to the point toward the top chord and mark where it meets the inside corner of the top chord and corner brace. Cut the board on this mark. Repeat this process. Place truss plates along the joists and secure between the chords and the lateral braces. Complete this process for the joists on both sides of the truss.