How Thick Roofing Plywood

Typical types of wood used for roof sheathing are oriented strand board known as osb and plywood the most popular being osb.

How thick roofing plywood.

That s considered to be the minimum. That s considered to be the minimum. 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. An exception to this standard however may occur if you intend to install slate concrete or tile shingles on your roof.

Plywood is often sold in 1 4 1 2 or 3 4 nominal thicknesses but the actual thickness is often 1 32 thinner. In this case plywood should be a minimum of 3 8 inch thick. Loads will vary with the pitch of the roof. Unlike with plywood siding the plywood sheet to be used for sheathing should be at least 3 8 inch thick.

Although specialty plywood can have any number of plies above three most plywood is categorized as 3 ply 5 ply or multi ply. Because the actual thickness may vary measuring the plywood is the only accurate way to determine its thickness. With edge support and the same snow load 3 8 inch osb can be used. Most roofs will be sheathed in plywood at least 3 8 inch thick.

That will suffice on a roof with rafters set 16 inches apart with minimal roof loads. However you may need to consider bolstering the plywood thickness for a roof that has a higher load. Sheathing sizes osb and plywood come in thicknesses ranging from 5 16 to 3 4 inch and the thickness needed for a particular roof depends on several factors including rafter spacing expected load. A 3 4 sheet is actually 23 32 thick.

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. 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. 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.