Span Rating

The Span Rating denotes the maximum permitted centre to centre spacing of supports, (in inches) over which the panels should be installed in normal construction.

It is particularly important for  Rated Sheathing and Rated Sturd-I-Floor, where the Span Rating is needed when the long panel dimension or strength axis is across two or more supports.

The appearance of the Span Rating takes the form of a fraction, such as 32/16, in rated sheathing panels. The left hand number denotes the maximum centre to centre spacing of supports (in inches) when the panel is used for roof sheathing (sarking), while the right hand number denotes the maximum centre to centre spacing when the panel is used for subflooring.

Sheathing panels with a roof Span Rating of 24 or greater may be used vertically or horizontally as wall sheathing over studs at 24 inch centres.  Those with roof Span Ratings of less than 24 inches may be used vertically or horizontally over studs spaced at 16 inches on centre.

Some panels are designated with a Span Rating of Wall-16 or Wall-24 which means that they have been specifically manufactured for use as wall sheathing over studs spaced at the designated distance apart.

APA Rated Sturd-I-Floor panels are designated specifically for single layer flooring applications where a solid face is required.  They are manufactured with Span Ratings of 16, 20, 24, 32 and 48 o.c.

Allowable uniformly distributed live loads at maximum span for Rated Sturd-I-Floor and Rated Sheathing is 100 lb/ft2 (1.48 kN/m2) for floors plus 10 lb/ft2 (0.15 kN/m2) dead load (65 lb/ft2 (0.97 kN/m2) total load for Sturd-I-Floor 48oc) and 30 lb/ft2 (0.45 kN/m2) snow load for roofs (35 lb/ft2 (0.52 kN/m2) for Rated Sheathing 48/24 or greater) plus 10 lb/ft2 (0.15 kN/m2) dead load.  Higher live loads can be achieved by placing the supports closer together than the maximum span indicated on APA trademarks.

Span Rating

Recommended OSB Thickness Performance Category1

3/8

7/16

15/32

1/2

19/32

5/8

23/32

3/4

7/8

1

1-1/8

APA Rated Sheathing

24/0

0.354 IN

(8.99 mm)

0.418 IN

(10.62 mm)

0.451 IN

(11.46 mm)

0.483 IN

(12.27 mm)

24/16

0.418 IN

(10.62 mm)

0.451 IN

(11.46 mm)

0.483 IN

(12.27 mm)

32/16

0.451 IN

(11.46 mm)

0.483 IN

(12.27 mm)

0.578 IN

(14.68 mm)

0.609 IN

(15.47 mm)

40/20

0.578 IN

(14.68 mm)

0.609 IN

(15.47 mm)

0.704 IN

(17.88 mm)

0.734 IN

(18.64 mm)

48/24

0.704 IN

(17.88 mm)

0.734 IN

(18.64 mm)

0.849 IN

(21.56 mm)

APA Rated Sturd-I-Floor

16 oc

0.578 IN

(14.68 mm)

0.609 IN

(15.47 mm)

20 oc

0.578 IN

(14.68 mm)

0.609 IN

(15.47 mm)

24 oc

0.704 IN

(17.88 mm)

0.734 IN

(18.64 mm)

32 oc

0.849 IN

(21.56 mm)

0.970 IN

(24.64 mm)

48 oc

1.091 IN

(27.71 mm)

1 Manufacturer’s stated thickness is denominated in 1/1000 of an inch in the trademarkMetric equivalents do not appear in the trade mark.  The predominant thickness label for each span rating is highlighted in bold type