For wood foundations that are not designed and installed in accordance with AWC PWF, the height of backfill against a foundation wall shall not exceed 4 feet (1219 mm). When the height of fill is more than 12 inches (305 mm) above the interior grade of a crawl space or floor of a basement, the thickness of the plywood sheathing shall meet the requirements of Table R404.2.3.
PLYWOOD GRADE AND THICKNESS FOR WOOD FOUNDATION CONSTRUCTION (30 pcf equivalent-fluid weight soil pressure)
| HEIGHT OF FILL (inches) | STUD SPACING (inches) | FACE GRAIN ACROSS STUDS | FACE GRAIN PARALLEL TO STUDS | ||||
| Gradea | Minimum thickness (inches) | Span rating | Gradea | Minimum thickness (inches)b, c | Span rating | ||
| 24 | 12 | B | 15/32 | 32/16 | A | 15/32 | 32/16 |
| B | 15/32c | 32/16 | |||||
| 16 | B | 15/32 | 32/16 | A | 15/32c | 32/16 | |
| B | 19/32c (4, 5 ply) | 40/20 | |||||
| 36 | 12 | B | 15/32 | 32/16 | A | 15/32 | 32/16 |
| B | 15/32c (4, 5 ply) | 32/16 | |||||
| B | 19/32 (4, 5 ply) | 40/20 | |||||
| 16 | B | 15/32c | 32/16 | A | 19/32 | 40/20 | |
| B | 23/32 | 48/24 | |||||
| 48 | 12 | B | 15/32 | 32/16 | A | 15/32c | 32/16 |
| B | 19/32c(4, 5 ply) | 40/20 | |||||
| 16 | B | 19/32 | 40/20 | A | 19/32c | 40/20 | |
| A | 23/32 | 48/24 | |||||
For SI: 1 inch = 25.4 mm, 1 foot = 304.8 mm, 1 pound per cubic foot = 0.1572 kN/m3.
Plywood shall be of the following minimum grades in accordance with DOC PS 1 or DOC PS 2:
DOC PS 1 Plywood grades marked:
1.1. Structural I C-D (Exposure 1).
1.2. C-D (Exposure 1).
DOC PS 2 Plywood grades marked:
2.1. Structural I Sheathing (Exposure 1).
2.2. Sheathing (Exposure 1).
Where a major portion of the wall is exposed above ground and a better appearance is desired, the following plywood grades marked exterior are suitable:
3.1. Structural I A-C, Structural I B-C or Structural I C-C (Plugged) in accordance with DOC PS 1.
3.2. A-C Group 1, B-C Group 1, C-C (Plugged) Group 1 or MDO Group 1 in accordance with DOC PS 1.
3.3. Single Floor in accordance with DOC PS 1 or DOC PS 2.
- Minimum thickness 15/32 inch, except crawl space sheathing shall have not less than 3/8 inch for face grain across studs 16 inches on center and maximum 2-foot depth of unequal fill.
- For this fill height, thickness and grade combination, panels that are continuous over less than three spans (across less than three stud spacings) require blocking 16 inches above the bottom plate. Offset adjacent blocks and fasten through studs with two 16d corrosion-resistant nails at each end.