Roof Sheathing Span Rating

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

Roof sheathing span rating.

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. 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. Installation details shall conform to sections 2304 7 1 and 2304 7 2 for floor and roof sheathing respectively. 1 inch 25 4 mm.

The span rating on sheathing span panels appears as two numbers separated by a slash e g 32 16 or 48 24. All rated siding panels may be applied horizontally direct to studs 16 or 24 inches on center provided horizontal joints are blocked. 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. Typical size is 4 ft x 8 ft but other sizes may also be produced.

Span ratings span rating numbers for sheathing span and floor span indicate the maximum spacing of supports over which the panels should be placed. Roof sheathing attaches to the surface of the rafters or trusses to form the structural skin of the roof. 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.

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. Panels and lap siding bearing a span rating of 24 oc may be used direct to studs 24 inches on center. Most roofs will be sheathed in plywood at least 3 8 inch thick. Allowable spans for lumber floor and roof sheathing a b for si.

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. Some products feature a two span rating such as 24 16. Loads will vary with the pitch of the roof.

That will suffice on a roof with rafters set 16 inches apart with minimal roof loads. Commonly square edge but may be produced with tongue and groove edges. The first number is the maximum on center o c support spacing in inches for roof sheathing. 2 4 common performance categories and corresponding span ratings performance category span rating 3 8 24 0 7 16 24 16.