Roof Sheathing Material Thickness

Roof sheathing attaches to the surface of the rafters or trusses to form the structural skin of the roof.

Roof sheathing material thickness.

And if you re still wondering what roof sheathing is and what materials are typically used read on and satisfy your curiosity. Correct installation of roof sheathing will ensure the best performance and help reduce complaints and callbacks. Unlike with plywood siding the plywood sheet to be used for sheathing should be at least 3 8 inch thick. Common roof sheathing applications and installation recommendations are described in the related publications listed at right.

Steeper roofs tend to have thinner sheathing due to not much weight being applied to the roof while flat and low sloop roofs that are likely to gather weight from precipitation or people walking on it. That will suffice on a roof with rafters set 16 inches apart with minimal roof loads. I just read somewhere actually in taunton press roofing with asphalt shingles book that one should consider using sheathing thicker than code to avoid sagging between rafters. Cdx works fine in 1 2 or 5 8 thickness.

As per code in my area ottawa canada i plan on using 3 8 plywood for sheathing. Sheathing comes in different thicknesses and what type of roof you have will help designate what type of thickness you need. And for wood structural panel sheathing r803 2 2 allowable spans. The common grade of plywood for roof sheathing is cdx.

Many code requirements are not inspected. Roof sheathing materials plywood. Comes in standard 4 by 8 foot sheets is strong durable and relatively light. According to 2009 irc table r803 1 minimum thickness of lumber roof sheathing.

Malcolm i almost always use 5 8 zip sheathing on roofs and metal roofing installers have never questioned it. Several factors must be considered when determining appropriate roof sheathing thickness such as the. The roof covering will be asphalt shingles. It also holds roofing nails well.

Loads will vary with the. You would go to table r503 2 1 1 1 to determine minimum nominal panel thickness. 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. For information on large panelized roof systems refer to the commercial construction application section.

Typical types of wood used for roof sheathing are oriented strand board known as osb and plywood. I ve never used commodity osb on a roof but it s probably fine in 5 8 thickness and possibly in 1 2 thickness. It spans the rafters to support the roofing and in the case of panel sheathing such as plywood or osb it acts as a diaphragm with the walls to resist horizontal loads. Minimum thickness most roofs will be sheathed in plywood at least 3 8 inch thick.