| TABLE 29 |
| PLYWOOD THICKNESS AND
MAXIMUM SPANS FOR ROOF DECKS UNDER SPECIAL COATINGS(c) |
| Grade |
Minimum Plywood
Thickness(in.) |
Maximum
Support Spacing (in.) |
Nail Type &
Size(b) |
Maximum Nail
Spacing (in.) |
| APA A-C EXT
APA B-C EXT
APA C-C PLUGGED EXT |
Group 1 |
Group 2
&3 |
Group 4 |
Supported Panel Edges |
Intermediate Supports |
| 11/32 |
16 |
- |
- |
8d common smooth(a)
or ring- or screw-shank |
6 |
12 |
| 15/32,1/2 |
24 |
24 |
16 |
8d common smooth(a)
or ring- or screw-shank |
6 |
12 |
| 19/32,5/8 |
32 |
24 |
24 |
8d ring- or
screw-shank |
6 |
12 |
| 23/32,3/4 |
40 |
32 |
32 |
8d ring- or
screw-shank |
6 |
12 |
| 7/8 |
48 |
40 |
40 |
8d ring- or
screw-shank |
6 |
12(d) |
(a)Use only deformed-shank nails for curved surfaces.
(b) Nail type, size and spacing may vary for diaphragm
designs.
(c) All panels will support at least 30 psf live load plus
10 psf dead load at maximum span.
(d) For spans 48 inches or greater,space nails maximum 6
inches at all supports.
structural decks, 15/32 inch or thicker panels should be considered
for best performance over uneven surfaces or when rain or highs humidity is anticipated
prior to application of roof coating. Use corrosion-resistant fasteners sized and spaced
as recommended in Table 8.
APA Panel Soffits
Recommended spans for open and closed APA panel soffits are given in
Tables 30 and 31. The recommendations in Table
30 for open soffits also apply to combined or/ceiling construction. Panels are
assumed continuous over two or more spans with the long dimension or strength axis across
supports for both applications. For appearance purposes in open soffit
construction, provide blocking, tongue-and-groove edges, or other suitable edge support.
Panels with support at least 30 psf live load, plus 10 psf dead load.
For open soffit and nonstructural ceiling construction, panels
designated Exposure 1 are recommended as a minimum (check local building code) where
appearance is not a major consideration. Only Exterior panels should be used of closed
soffits.
At eaves where Exposure 1 sheathing is used for roof decking,
protect panel edges against direct exposure to the weather with fascia trim. Although
unsounded and touch-sanded grades of plywood are often used for applications such as
soffits, optimum appearance and finish performance is attained by using panels with
textured or sanded A-grade faces. For panel grades other than APA RATED SIDING
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