ICC Subscriptions
 
2304.7 Floor and roof sheathing.

TABLE 2304.7(1) ALLOWABLE SPANS FOR LUMBER FLOOR AND ROOF SHEATHINGa,b


SPAN (inches)
MINIMUM NET THICKNESS (inches) OF LUMBER PLACED
Perpendicular to supports
Diagonally to supports
Surfaced dryc
Surfaced unseasoned
Surfaced dryc
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.

a.   Installation details shall conform to Sections 2304.6.1 and 2304.6.2 for floor and roof sheathing, respectively.

b.   Floor or roof sheathing conforming with this table shall be deemed to meet the design criteria of Section 2304.6.

c.   Maximum 19 percent moisture content.

TABLE 2304.7(2) SHEATHING LUMBER, MINIMUM GRADE REQUIREMENTS: BOARD GRADE


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 2304.7(3) ALLOWABLE SPANS AND LOANS FOR WOOD STRUCTURAL PANEL SHEATHING AND SINGLE-FLOOR GRADES CONTINUOUS OVER TWO OR MORE SPANS WITH STRENGTH AXIS PERPENDICULAR TO SUPPORTSa,b


SHEATHING GRADES
ROOFc
FLOORd
Panel span rating roof/floor span
Panel thickness (inches)
Maximum span (inches)
Loade (psf)
Maximum span (inches)
With edge supportf
Without edge support
Total load
Live load
12/0
5/16
12
12
40
30
0
16/0
5/16, 3/8
16
16
40
30
0
20/0
5/16, 3/8
20
20
40
30
0
24/0
3/8, 7/16, ½
24
20g
40
30
0
24/16
 7/16, ½
24
24
50
40
16
32/16
15/32, ½, 5/8
32
28
40
30
16h
40/20
19/32, 5/8, 3/4, 7/8
40
32
40
30
20h,i
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, 1 1/8
60
48
45
35
32
SINGLE FLOOR GRADES
ROOFc
FLOORd
Panel span rating
Panel thickness (inches)
Maximum span (inches)
Loade (psf)
Maximum span (inches)
With edge supportf
Without edge support
Total load
Live load
16 oc
½, 19/32, 5/8
24
24
50
40
16h
20 oc
19/32, 5/8, 3/4
32
32
40
30
20h,i
24 oc
23/32, 34
48
36
35
25
24
32 oc
7/8, 1
48
40
50
40
32
48 oc
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.

a.   Applies to panels 24 inches or wider.

b.   Floor and roof sheathing conforming with this table shall be deemed to meet the design criteria of Section 2304.7.

c.   Uniform load deflection limitations 1/180 of span under live load plus dead load, 1/240 under live load only.

d.   Panel edges shall have approved tongue-and-groove joints or shall be supported with blocking unless ¼-inch minimum thickness underlayment or 1 ½ 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 (psf) except the span rating of 48 inches on center is based on a total load of 65 psf.

e.   Allowable load at maximum span.

f.   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 diaphragms requirements.

g.   For ½-inch panel, maximum span shall be 24 inches.

h.   Is permitted to be 24 inches on center where ¾-inch wood strip flooring is installed at right angles to joist.

j.   Is permitted to be 24 inches on center for floors where 1½ inches of cellular or lightweight concrete is applied over the panels.

TABLE 2304.7(4) ALLOWABLE SPAN FOR WOOD STRUCTURAL PANEL COMBINATION SUBFLOOR-UNDERLAYMENT (SINGLE FLOOR)a,b (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 groupc
Thickness (inches)
1
½
5/8
3/4


2, 3
5/8
3/4
7/8


4
3/4
7/8
1


Single floor
span ratingd
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.

a.   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 pr square foot (psf) except allowable total uniform load for 11/8-inch wood structural panels over joists spaced 48 inches on center is 65 psf. Panel edges shall have approved tongue-and-groove joints or shall be supported with blocking, unless ¼-inch minimum thickness underlayment or 1 ½ inches.

b.   Floor panels conforming with this table shall be deemed to meet the design criteria of Section 2304.7.

c.   Applicable to all grades of sanded exterior-type plywood. See DOC PS 1 for plywood species groups.

d.   Applicable to Underlayment grade, C-C (Plugged) plywood, and Single Floor grade wood structural panels.

TABLE 2304.7(5) 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,b


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
35c
45c
½
24
40c
50c
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
½
24
25
30
19/32
24
40c
50c
5/8
24
45c
55c
23/32, 3/4
24
60c
65c

For SI:   1 inch = 25.4 mm, 1 pound per square foot = 0.0479 kN/m2.

a.   Roof sheathing conforming with this table shall be deemed to meet the design criteria of Section 2304.7.

b.   Uniform load deflection limitations 1/180 of span under live load plus dead load, 1/240 under live load only. Edges shall be blocked with lumber or other approved type of edge supports.

c.   For composite and four-ply plywood structural panel, load shall be reduced by 15 pounds per square foot.

2304.7.1 Structural floor sheathing.


Structural floor sheathing shall be designed in accordance with the general provisions of this code and the special provisions in this section.

Floor sheathing conforming to the provisions of Table 2304.7(1), 2304.7(2), 2304.7(3), or 2304.7(4) shall be deemed to meet the requirements of this section.

2304.7.2 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 2304.7(1), 2304.7(2), 2304.7(3), or 2304.7(5) shall be deemed to meet the requirements of this section. Wood structural panel roof sheathing shall be bonded by exterior glue.