Standard Plywood Sheathing on the Exterior of a House

Description

• Manufacturers produce standard plywood by combining an odd number of thin layers of wood together to make a single panel. A key part of making strong plywood involves positioning a layer so that its grain runs at a right angle to the grain of any adjacent layer. Plywood made for exterior applications has a greater durability than plywood made exclusively for interior use, such as subflooring. The thickness of standard plywood can vary, with most panels being in the 1/4 inch to 3/4 inch range.

Walls

• A sheathing that acts an integral part of the home's framing is called a structural sheathing. Plywood functions as a structural sheathing, providing a way to connect the studs and creating a nailing base for the siding material. Using panels at least 1/2-inch-thick works best in most situations, according to Hometips.com. Panels fasten to the wall studs with 6d nails. Space the nails 6 inches apart on the ends and 12 inches apart in the middle.

Roof

• Plywood makes an excellent roof sheathing. It has an advantage over its main competitor, oriented strand board, or OSB, in that it responds better to exposure to moisture. OSB tends to hold water when wet. The longer a wood product retains moisture, the more susceptible it becomes to rot. Plywood has some swelling when wet, but it dries out faster and reverts to its original size more quickly than OSB. Most builders use 3/8-inch-thick plywood panels for roof sheathing.

Grade

• The plywood industry has instituted a grading system for plywood, with standard grades ranging from A to D. The "A'' grade represents the highest quality material, with the panel having few defects. Grade "D" plywood contains significant visible defects, with "B" and "C" grades falling in between. Each side of a panel receives a grade based on its appearance, so a single panel will have two grades, such as "AC," depending on the quality of each side.