Sheathing with Plywood Panels

1. Nailing the sheathing. Slip a Z-shaped piece of flashing under the back side of the truss panel and then hold a full-length plywood pan el under it while a helper nails the panel to the studs. Put nails every 6” around the edges of the panel every 12” along the intermediate studs. Continue attaching the plywood panels in this way.

For a simple outdoor structure like the one shown, you can save time and money on sheathing and siding by using sheets of exterior- grade plywood 4 ft. wide to serve as both. Manufacturers now make plywood in a variety of textures and simulate all but the most intricate siding patterns.

You can get this type of paneling in 8-, 9-, or 10-ft. lengths; when ordering, make sure you specify an exterior-grade plywood, made with waterproof glues. If you are setting your studs 24” apart, make sure the plywood is the extra-thick kind designed for this spacing. If you plan to set the panels against the studs horizontally, put blocking between the studs 4 ft. from the bottom of the wall to serve as a nailing surface.

To make sure that the panels are water tight, use a Z-cap flashing between the end-truss panels and the side-wall panels. Then use sealant (Step 2) to caulk between the panel joints unless you use panels with special tongue-and-groove or shiplap edges. Protect the corners of the building with corner molding and use galvanized nails to prevent rust stains.

2. Weatherproofing the siding. Caulk the gaps between the plywood panels with a polyurethane or silicone sealant. Cover the exposed edges of the plywood at the corners of the building with strips of right-angle corner molding or, if you prefer, simply butt lengths of 1-by-3 and 1- by-4 lumber at the corners.