What Thickness of Plywood to Use for Roof Sheeting

Widths

• When buying plywood to use as the sheeting of a roof, don't buy plywood less than a half inch in thickness. Thin plywood isn't thick enough to support your weight when you're building the roof. Five-eighths of an inch is also acceptable, as is three-quarter inch plywood. Each of these thicknesses is enough to provide the roof with a solid foundation and support the average person working on the roof.

Thicker Wood

• Logic might dictate that the thicker the plywood, the stronger and the safer the roof will be. While this argument is true, using anything more than three-quarter inch plywood is unnecessary. Not only will this thickness of wood cost you more money than buying a thinner type, it's heavier and more difficult to get up to the roof and position as necessary.

Caution

• Although half-, five-eighths- and three-quarter-inch plywood are all common for roof sheeting, be cautious when working on the roof. Plywood of this thickness is unlikely to break under reasonable weight, but step on the plywood over the roof joists as much as possible. Otherwise, stay low and keep your weight distributed to avoid putting excessive pressure on one area of the sheeting.

Installation

• Cut the plywood to the correct size for the roof and hammer it to the roof joists. Cover the entire plywood with tar paper. Overlap the sheets of tar paper and staple them to the plywood. Then, finish the roof by nailing asphalt shingles, wood shingles or sheets of aluminum to the roof.