What's the Optimal Thickness for Roof Sheathing? What's the Optimal Thickness for Roof Sheathing?

Determining the optimal roof sheathing thickness is a major factor in the strength and longevity of your roof structure.

Span Ratings

The material you use on your roof must have a span rating. A span rating is stamped on each piece of material you purchase. Usually these materials are either plywood or oriented strand board (OSB) and are purchased in 4 by 8 foot sheets. The required span rating is affected by the spacing on your rafters or roof trusses. The wider the space between your rafters, the thicker your material must be as thicker material has a higher span rating. The span rating is written in 2 numbers such as 24/16. The first number is how wide the span can be on a roof and the second number is how wide the span can be on a floor.

Deciding on Which Material to Use

Measure the distance or span between the centers of your rafters. This is the number you will be looking for when purchasing the materials for your roof. Check the span rating on the material to be sure it is manufactured to cover at least the span you are working with. Only use material designed for outdoor use on a roof.

Using the correct thickness of material for your application will help to ensure a solid, long lasting application.

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