Roof Sheathing Span Rating

Apa rated sheathing panels are produced as plywood or oriented strand board osb.

Roof sheathing span rating.

Panels and lap siding with a span rating of 16 oc may be applied direct to studs spaced 16 inches on center. Floor or roof sheathing conforming with this table shall be deemed to meet the design criteria of section 2304 7. That will suffice on a roof with rafters set 16 inches apart with minimal roof loads. The span rating indicates the maximum center to center spacing in inches of support over which panels can be installed.

Commonly square edge but may be produced with tongue and groove edges. Allowable spans for lumber floor and roof sheathing a b for si. Construction basics roof systems plywood and oriented strand board osb are used in roof sheathing systems ranging from simple single family residences to large commercial buildings. 2 4 common performance categories and corresponding span ratings performance category span rating 3 8 24 0 7 16 24 16.

Multi span normal duration of load dry conditions panels 24 inches or wider span rating b load governed by c strength axis a perpendicular to supports span center to center of supports inches parallel to supports span center to center of supports inches 12 16 19 2 24 30 32 36 40 48. The first number is the maximum on center o c support spacing in inches for roof sheathing. Roof sheathing attaches to the surface of the rafters or trusses to form the structural skin of the roof. 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.

Some products feature a two span rating such as 24 16. Uniform loads psf on apa rated plywood sheathing. The first number represents the maximum support spacing for a roof application and the second number indicates a maximum spacing of supports for flooring. Typical size is 4 ft x 8 ft but other sizes may also be produced.

All rated siding panels may be applied horizontally direct to studs 16 or 24 inches on center provided horizontal joints are blocked. Panels and lap siding bearing a span rating of 24 oc may be used direct to studs 24 inches on center. Panels are available that carry apa series mobile home roof sheathing rating n 216r. The span rating on sheathing span panels appears as two numbers separated by a slash e g 32 16 or 48 24.

Span ratings span rating numbers for sheathing span and floor span indicate the maximum spacing of supports over which the panels should be placed. Sheathing panels 3 8 category may be installed perpendicular or parallel to supports spaced a maximum of 16 o c and will support a 30 psf live load without exceeding a deflection limit of 1 180. Common roof sheathing applications and installation recommendations are described in the related publications listed at right. Most roofs will be sheathed in plywood at least 3 8 inch thick.