How Thick Roofing Plywood

Unlike with plywood siding the plywood sheet to be used for sheathing should be at least 3 8 inch thick.

How thick roofing plywood.

That s considered to be the minimum. This minimum will only work if the rafters are set 16 inches apart at most and if the roof doesn t have too much load. Typical types of wood used for roof sheathing are oriented strand board known as osb and plywood the most popular being osb. Sheets of 7 16 inch thick with no edge support can be used in an area where the snow load is 30 pounds per square foot.

3 ply is one of the most common types of plywood. In this case plywood should be a minimum of 3 8 inch thick. A 3 4 sheet is actually 23 32 thick. That will suffice on a roof with rafters set 16 inches apart with minimal roof loads.

A 1 2 sheet is actually 15 32 thick. Loads will vary with the pitch of the roof. Plywood is often sold in 1 4 1 2 or 3 4 nominal thicknesses but the actual thickness is often 1 32 thinner. A roof that lays practically flat will have a much heavier load than a steeper roof that allows rain snow and ice to roll right off.

With edge support and the same snow load 3 8 inch osb can be used. Standard roof sheathing which consists of 4 by 8 sheets of plywood or oriented strand board or osb is 1 2 inch thick and attaches directly to the roof rafters or the roof trusses. Although specialty plywood can have any number of plies above three most plywood is categorized as 3 ply 5 ply or multi ply. That s considered to be the minimum.

Because the actual thickness may vary measuring the plywood is the only accurate way to determine its thickness. Most roofs will be sheathed in plywood at least 3 8 inch thick. However you may need to consider bolstering the plywood thickness for a roof that has a higher load.