Determining the Correct Floor Sheathing Thickness

Determining the correct floor sheathing thickness is important to the strength, performance, and longevity of your structure.

Span Ratings

The material that you use on your floor 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 floor joists. The wider the space between your joists, 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 floor joists. This is the number you will be looking for when purchasing the materials for your floor. Check the span rating on the material to be sure it is manufactured to cover at least the span you are working with.

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