Code of Massachusetts Regulations › 780 CMR - STATE BOARD OF BUILDING REGULATIONS AND STANDARDS › Chapter 23 - Wood › Section 2304 - GENERAL CONSTRUCTION REQUIREMENTS › Subsection 2304.7 - Floor and roof sheathing

Current through Register 1525, July 5, 2024
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 2304.7.1 and 2304.7.2 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 2304.7.
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 LOADS 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
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
20g
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
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, 11/8
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 o.c.
1/2,19/32,5/ 8
24
24
50
40
16h
20 o.c.
19/32,5/8,3/ 4
32
32
40
30
20h,i
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.
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 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.
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 diaphragm requirements.
g. For 1/2-inch panel, maximum
							 span shall be 24 inches.
h. Span is permitted to be 24 inches on
							 center where 3/4-inch wood strip flooring is installed at right angles to
							 joist.
i. 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.
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
1/2
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 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.
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
1/2
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
1/2
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.