Roof Sheathing Thickness

The minimum thickness of lumber roof sheathing should conform to table 1 below.

Roof sheathing thickness.

Roof sheathing comes in grid marked 4 by 8 foot sheets and should be installed perpendicular to the frame. The typical thickness range for sheathing is 3 8 to 3 4 inch. That s considered to be the minimum. Otherwise no clips just be sure to space all edges 1 8 as listed right on the sheathing label which goes down so the inspector can read it from inside it s also the waxed side which is safer.

Roof sheathing conforming with this table shall be deemed to meet the design criteria of section 2304 7. 1 inch 25 4 mm 1 pound per square foot 0 0479 kn m2. Uniform load deflection limitations 1 180 of span under live load plus dead load 1 240 under live load only. You may be able to measure the thickness of the roof decking material with a simple ruler as seen in the photo below taken during an actual inspection.

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. That will suffice on a roof with rafters set 16 inches apart with minimal roof loads. Loads will vary with the pitch of the roof. Roof sheathing thickness unlike with plywood siding the plywood sheet to be used for sheathing should be at least 3 8 inch thick.

Most roofs will be sheathed in plywood at least 3 8 inch thick.