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2304.8 Floor and Roof Sheathing
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Structural floor sheathing and structural roof sheathing shall comply with Sections 2304.8.1 and 2304.8.2, respectively.
TABLE 2304.8(1)
ALLOWABLE SPANS FOR LUMBER FLOOR AND ROOF SHEATHING
| SPAN (inches) | MINIMUM NET THICKNESS (inches) OF LUMBER PLACED | |||
| Perpendicular to supports | Diagonally to supports | |||
| Surfaced drya | Surfaced unseasoned | Surfaced drya | Surfaced unseasoned | |
| Floors | ||||
| 24 | 3/4 | 25/32 | 3/4 | 25/32 |
| 16 | 5/8 | 11/16 | 5/8 | 11/16 |
| Roofs | ||||
| 24 | 5/8 | 11/16 | 3/4 | 25/32 |
For SI: 1 inch = 25.4 mm.
- Maximum 19-percent moisture content.
| SOLID FLOOR OR ROOF SHEATHING | SPACED ROOF SHEATHING | GRADING RULES |
| Utility | Standard | NLGA, WCLIB, WWPA |
| 4 common or utility | 3 common or standard | NLGA, WCLIB, WWPA, NSLB or NELMA |
| No. 3 | No. 2 | SPIB |
| Merchantable | Construction common | RIS |
TABLE 2304.8(3)
ALLOWABLE SPANS AND LOADS FOR WOOD STRUCTURAL PANEL SHEATHING AND SINGLE-FLOOR GRADES CONTINUOUS OVER TWO OR MORE SPANS WITH STRENGTH AXIS PERPENDICULAR TO SUPPORTSa
| SHEATHING GRADES | ROOFb | FLOORc | ||||
| Panel span rating roof/floor span | Panel thickness (inches) | Maximum span (inches) | Loadd (psf) | Maximum span (inches) | ||
| With edge supporte | Without edge support | Total load | Live load | |||
| 16/0 | 3/8 | 16 | 16 | 40 | 30 | 0 |
| 20/0 | 3/8 | 20 | 20 | 40 | 30 | 0 |
| 24/0 | 3/8, 7/16, 1/2 | 24 | 20f | 40 | 30 | 0 |
| 24/16 | 7/16, 1/2 | 24 | 24 | 50 | 40 | 16 |
| 32/16 | 15/32, 1/2, 5/8 | 32 | 28 | 40 | 30 | 16g |
| 40/20 | 19/32, 5/8, 3/4, 7/8 | 40 | 32 | 40 | 30 | 20g,h |
| 48/24 | 23/32, 3/4, 7/8 | 48 | 36 | 45 | 35 | 24 |
| 54/32 | 7/8, 1 | 54 | 40 | 45 | 35 | 32 |
| 60/32 | 7/8, 11/8 | 60 | 48 | 45 | 35 | 32 |
| SINGLE FLOOR GRADES | ROOFb | FLOORc | ||||
| Panel span rating | Panel thickness (inches) | Maximum span (inches) | Loade (psf) | Maximum span (inches) | ||
| With edge supporte | Without edge support | Total load | Live load | |||
| 16 o.c. | 1/2, 19/32, 5/8 | 24 | 24 | 50 | 40 | 16g |
| 20 o.c. | 19/32, 5/8, 3/4 | 32 | 32 | 40 | 30 | 20g,h |
| 24 o.c. | 23/32, 3/4 | 48 | 36 | 35 | 25 | 24 |
| 32 o.c. | 7/8, 1 | 48 | 40 | 50 | 40 | 32 |
| 48 o.c. | 13/32, 11/8 | 60 | 48 | 50 | 40 | 48 |
For SI: 1 inch = 25.4 mm, 1 pound per square foot = 0.0479 kN/m2.
- Applies to panels 24 inches or wider.
- Uniform load deflection limitations 1/180 of span under live load plus dead load, 1/240 under live load only.
- Panel edges shall have approved tongue-and-groove joints or shall be supported with blocking unless 1/4-inch minimum thickness underlayment or 11/2 inches of approved cellular or lightweight concrete is placed over the subfloor, or finish floor is 3/4-inch wood strip. Allowable uniform load based on deflection of 1/360 of span is 100 pounds per square foot except the span rating of 48 inches on center is based on a total load of 65 pounds per square foot.
- Allowable load at maximum span.
- Tongue-and-groove edges, panel edge clips (one midway between each support, except two equally spaced between supports 48 inches on center), lumber blocking or other. Only lumber blocking shall satisfy blocked diaphragm requirements.
- For 1/2-inch panel, maximum span shall be 24 inches.
- Span is permitted to be 24 inches on center where 3/4-inch wood strip flooring is installed at right angles to joist.
- Span is permitted to be 24 inches on center for floors where 11/2 inches of cellular or lightweight concrete is applied over the panels.
ALLOWABLE SPAN FOR WOOD STRUCTURAL PANEL COMBINATION SUBFLOOR-UNDERLAYMENT (SINGLE FLOOR)a (Panels Continuous Over Two or More Spans and Strength Axis Perpendicular to Supports)
| IDENTIFICATION | MAXIMUM SPACING OF JOISTS (inches) | ||||
| 16 | 20 | 24 | 32 | 48 | |
| Species groupb | Thickness (inches) | ||||
| 1 | 1/2 | 5/8 | 3/4 | — | — |
| 2, 3 | 5/8 | 3/4 | 7/8 | — | — |
| 4 | 3/4 | 7/8 | 1 | — | — |
| Single floor span ratingc | 16 o.c. | 20 o.c. | 24 o.c. | 32 o.c. | 48 o.c. |
For SI: 1 inch = 25.4 mm, 1 pound per square foot = 0.0479 kN/m2.
- Spans limited to value shown because of possible effects of concentrated loads. Allowable uniform loads based on deflection of 1/360 of span is 100 pounds per square foot except allowable total uniform load for 11/8-inch wood structural panels over joists spaced 48 inches on center is 65 pounds per square foot. Panel edges shall have approved tongue-and-groove joints or shall be supported with blocking, unless 1/4-inch minimum thickness underlayment or 11/2 inches of approved cellular or lightweight concrete is placed over the subfloor, or finish floor is 3/4-inch wood strip.
- Applicable to all grades of sanded exterior-type plywood. See DOC PS 1 for plywood species groups.
- Applicable to Underlayment grade, C-C (Plugged) plywood, and Single Floor grade wood structural panels.
ALLOWABLE LOAD (PSF) FOR WOOD STRUCTURAL PANEL ROOF SHEATHING CONTINUOUS OVER TWO OR MORE SPANS AND STRENGTH AXIS PARALLEL TO SUPPORTS (Plywood structural panels are five-ply, five-layer unless otherwise noted)a
| PANEL GRADE | THICKNESS (inch) | MAXIMUM SPAN (inches) | LOAD AT MAXIMUM SPAN (psf) | |
| Live | Total | |||
| Structural I sheathing | 7/16 | 24 | 20 | 30 |
| 15/32 | 24 | 35b | 45b | |
| 1/2 | 24 | 40b | 50b | |
| 19/32, 5/8 | 24 | 70 | 80 | |
| 23/32, 3/4 | 24 | 90 | 100 | |
| Sheathing, other grades covered in DOC PS 1 or DOC PS 2 | 7/16 | 16 | 40 | 50 |
| 15/32 | 24 | 20 | 25 | |
| 1/2 | 24 | 25 | 30 | |
| 19/32 | 24 | 40b | 50b | |
| 5/8 | 24 | 45b | 55b | |
| 23/32, 3/4 | 24 | 60b | 65b | |
For SI: 1 inch = 25.4 mm, 1 pound per square foot = 0.0479 kN/m2.
2304.8.1 Structural Floor Sheathing
2304.8.2 Structural Roof Sheathing
Structural roof sheathing shall be designed in accordance with the general provisions of this code and the special provisions in this section.
Roof sheathing conforming to the provisions of Table 2304.8(1), 2304.8(2), 2304.8(3) or 2304.8(5) shall be deemed to meet the requirements of this section. Wood structural panel roof sheathing shall be of a type manufactured with exterior glue (Exposure 1 or Exterior).
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