How to Sheath Floor Trusses

Subfloor made from plywood is screwed into floor trusses.

Sometimes trusses are used as floor joists in floor systems. The difference between a joist and a truss is that a joist is a solid piece of wood seated on its narrow side to provide rigidity for a subfloor. In flooring, a truss is a wooden framework that, when viewed from the side, looks like a series of triangles sandwiched between horizontal slats of lumber. Despite the differences between these two floor supports, sheathing a truss is similar to sheathing a joist.

Things You'll Need

• C-D grade plywood
• 1½ inch wood screws
• Drill
• T-square
• Circular saw
• Protective eyeglasses

Instructions

1. Center a C-D grade plywood panel over the center truss, with the grain of the plywood running perpendicular to the trusses and the C side up. This panel is properly placed when it is laying in the approximate center of the room with each end of the panel centered over a truss.

2. Screw the panel into the trusses with 1½-inch wood screws. Use a drill to insert screws every 6 inches along the ends of the panel and every 12 inches throughout the center of the panel.

3. Lay down subsequent panels on trusses surrounding the panel you started with. Stagger the panels in each course so that the panels appear to stair-step across the floor of the room, the way bricks stair-step across a wall. Leave a gap of 1/8 inch between panels to allow for expansion. Screw the panels into the trusses following the same procedure in Step 2.

4. Cut the panels to fit the outer limits of the room if full-sized panels do not fit in the remaining space. Use a circular saw to cut the panels into the space available.

Tips & Warnings

• Follow all building codes and instructions provided by the truss manufacturer.

• Use a T-square to ensure that the panels are laid perpendicular to the trusses.

• For extra protection against floor squeaks, lay adhesive caulking beneath each panel on the floor trusses.

• Wear protective eye glasses when operating a circular saw.

References

• Realtor.com: Installing a Subfloor Over a Joist System