Code of Massachusetts Regulations
780 CMR - STATE BOARD OF BUILDING REGULATIONS AND STANDARDS
Chapter 23 - Wood
Section 2306 - ALLOWABLE STRESS DESIGN
Subsection 2306.2 - Wood diaphragms

Universal Citation: 780 CMR MA Code of Regs 2306.2

Current through Register 1531, September 27, 2024

2306.2.1 Wood structural panel diaphragms. Wood structural panel diaphragms shall be designed and constructed in accordance with AF & PA SDPWS. Wood structural panel diaphragms are permitted to resist horizontal forces using the allowable shear capacities set forth in Table 2306.2.1(1) or 2306.2.1(2). The allowable shear capacities in Tables 2306.2.1(1) and 2306.2.1(2) are permitted to be increased 40 percent for wind design.

TABLE 2306.2.1(1) ALLOWABLE SHEAR (POUNDS PER FOOT) FOR WOOD STRUCTURAL PANEL DIAPHRAGMS WITH FRAMING OF DOUGLAS FIR-LARCH, OR SOUTHERN PINEa FOR WIND OR SEISMIC LOADINGh

PANEL GRADE COMMON NAIL SIZE OR STAPLEf LENGTH AND GAGE MINIMUM FASTENER PENETRATION IN FRAMING (inches) MINIMUM NOMINAL PANEL THICKNESS (inch) MINIMUM NOMINAL
WIDTH OF FRAMING MEMBERS AT ADJOINING PANEL
EDGES AND BOUNDARIESg (inches) 		BLOCKED DIAPHRAGMS UNBLOCKED DIAPHRAGMS
Fastener spacing (inches) at diaphragm boundaries (all cases) at continuous panel edges parallel to load (Cases 3, 4), and at all panel edges (Cases 5, 6)b Fasteners spaced 6 max. at supported edgesb
6 4 2 1/2c 2c Case 1 (No unblocked edges or continuous joints parallel to load) All other configurations (Cases 2, 3, 4, 5 and 6)
Fastener spacing (inches) at other panel edges (Cases 1, 2, 3 and 4)b
6 6 4 3
Structural I grades 8d (2 1/2" x 0.131") 1 3/8 3/8 2 270 360 530 600 240 180
3 300 400 600 675 265 200
11/2 16 Gage 1 2 175 235 350 400 155 115
3 200 265 395 450 175 130
10dd (3" x 0.148") 1 1/2 15/32 2 320 425 640 730 285 215
3 360 480 720 820 320 240
11/2 16 Gage 1 2 175 235 350 400 155 120
3 200 265 395 450 175 130
Sheathing, single floor and other grades covered in DOC PS 1 and PS 2 6de (2" x 0.113") 11/4 3/8 2 185 250 375 420 165 125
8d (21/2" x 0.131") 13/8 3 210 280 420 475 185 140
2 240 320 480 545 215 160
3 270 360 540 610 240 180
11/2 16 Gage 1 2 160 210 315 360 140 105
3 180 235 355 400 160 120
8d (2 1/2" x 0.131") 1 3/8 7/16 2 255 340 505 575 230 170
3 285 380 570 645 255 190
11/2 16 Gage 1 2 165 225 335 380 150 110
3 190 250 375 425 165 125
8d (2 1/2" x 0.131") 1 3/8 15/32 2 270 360 530 600 240 180
3 300 400 600 675 265 200
10dd (3" x 0.148") 11/2 2 290 385 575 655 255 190
3 325 430 650 735 290 215
11/2 16 Gage 1 2 160 210 315 360 140 105
3 180 235 355 405 160 120
10dd (3" x 0.148") 11/2 19/32 2 320 425 640 730 285 215
3 360 480 720 820 320 240
13/4 16 Gage 1 2 175 235 350 400 155 115
3 200 265 395 450 175 130

TABLE 2306.2.1(1)-continued-ALLOWABLE SHEAR (POUNDS PER FOOT) FOR WOOD STRUCTURAL PANEL DIAPHRAGMS WITH FRAMING OF DOUGLAS FIR-LARCH, OR SOUTHERN PINEa FOR WIND OR SEISMIC LOADINGh

For SI: 1 inch = 25.4 mm, 1 pound per foot = 14.5939 N/m.
a. For framing of other species: (1) Find specific gravity for species of lumber in AF & PA NDS. (2) For staples find shear value from table above for Structural I panels (regardless of actual grade) and multiply value by 0.82 for species with specific gravity of 0.42 or greater, or 0.65 for all other species. (3) For nails find shear value from table above for nail size for actual grade and multiply value by the following adjustment factor: Specific Gravity Adjustment Factor = [1-(0.5 - SG)], where SG = Specific Gravity of the framing lumber. This adjustment factor shall not be greater than 1.
b. Space fasteners maximum 12 inches o.c. along intermediate framing members (6 inches o.c. where supports are spaced 48 inches o.c.).
c. Framing at adjoining panel edges shall be 3 inches nominal or wider, and nails at all panel edges shall be staggered where panel edge nailing is specified at 21/2 inches o.c. or less.
d. Framing at adjoining panel edges shall be 3 inches nominal or wider, and nails at all panel edges shall be staggered where both of the following conditions are met: (1) 10d nails having penetration into framing of more than 11/2 inches and (2) panel edge nailing is specified at 3 inches o.c. or less.
e. 8d is recommended minimum for roofs due to negative pressures of high winds.
f. Staples shall have a minimum crown width of 7/16 inch and shall be installed with their crowns parallel to the long dimension of the framing members.
g. The minimum nominal width of framing members not located at boundaries or adjoining panel edges shall be 2 inches.
h. For shear loads of normal or permanent load duration as defined by the AF & PA NDS, the values in the table above shall be multiplied by 0.63 or 0.56, respectively.

TABLE 2306.2.1(2) ALLOWABLE SHEAR (POUNDS PER FOOT) FOR WOOD STRUCTURAL PANEL BLOCKED DIAPHRAGMS UTILIZING MULTIPLE ROWS OF FASTENERS (HIGH LOAD DIAPHRAGMS) WITH FRAMING OF DOUGLAS FIR-LARCH OR SOUTHERN PINEa FOR WIND OR SEISMIC LOADINGb, g, h

PANEL GRADEc COMMON NAIL SIZE OR STAPLEf GAGE MINIMUM FASTENER PENETRATION IN FRAMING (inches) MINIMUM NOMINAL PANEL THICKNESS (inch) MINIMUM NOMINAL WIDTH OF FRAMING MEMBER AT ADJOINING PANEL EDGES AND BOUNDARIESe LINES OF FASTENERS BLOCKED DIAPHRAGMS
Cases 1 and 2d
Fastener Spacing Per Line at Boundaries (inches)
4 21/2 2
Fastener Spacing Per Line at Other Panel Edges (inches)
6 4 4 3 3 2
Structural I grades 10d common nails 11/2 15/32 3
4
4 		2
2
3 		605
700
875 		815
915
1,220 		875
1,005
1,285 		1,150
1,290
1,395 		-
-
- 		-
-
-
19/32 3
4
4 		2
2
3 		670
780
965 		880
990
1,320 		965
1,110
1,405 		1,255
1,440
1,790 		-
-
- 		-
-
-
23/32 3
4
4 		2
2
3 		730
855
1,050 		955
1,070
1,430 		1,050
1,210
1,525 		1,365
1,565
1,800 		-
-
- 		-
-
-
14 gage staples 2 15/32 3
4 		2
3 		600
860 		600
900 		860
1,160 		960
1,295 		1,060
1,295 		1,200
1,400
19/32 3
4 		2
3 		600
875 		600
900 		875
1,175 		960
1,440 		1,075
1,475 		1,200
1,795
Sheathing single floor and other grades covered in DOC PS 1 and PS 2 10d common nails 11/2 15/32 3
4
4 		2
2
3 		525
605
765 		725
815
1,085 		765
875
1,130 		1,010
1,105
1,195 		-
-
- 		-
-
-
19/32 3
4
4 		2
2
3 		650
755
935 		860
965
1,290 		935
1,080
1,365 		1,225
1,370
1,485 		-
-
- 		-
-
-
23/32 3
4
4 		2
2
3 		710
825
1,020 		935
1,050
1,400 		1,020
1,175
1,480 		1,335
1,445
1,565 		-
-
- 		-
-
-
14 gage staples 2 15/32 3
4 		2
3 		540
735 		540
810 		735
1,005 		865
1,105 		915
1,105 		1,080
1,195
19/32 3
4 		2
3 		600
865 		600
900 		865
1,130 		960
1,430 		1,065
1,370 		1,200
1,485
23/32 4 3 865 900 1,130 1,490 1,430 1,545

For SI: 1 inch = 25.4 mm, 1 pound per foot = 14.5939 N/m.
a. For framing of other species: (1) Find specific gravity for species of framing lumber in AF & PA NDS. (2) For staples, find shear value from table above for Structural I panels (regardless of actual grade) and multiply value by 0.82 for species with specific gravity of 0.42 or greater, or 0.65 for all other species. (3) For nails, find shear value from table above for nail size of actual grade and multiply value by the following adjustment factor: Specific Gravity Adjustment Factor = [ 1- (0.5 - SG)], where SG = Specific gravity of the framing lumber. This adjustment factor shall not be greater than 1.
b. Fastening along intermediate framing members: Space fasteners a maximum of 12 inches on center, except 6 inches on center for spans greater than 32 inches.
c. Panels conforming to PS 1 or PS 2.
d. This table gives shear values for Cases 1 and 2 as shown in Table 2306.2.1(1). The values shown are applicable to Cases 3, 4, 5 and 6 as shown in Table 2306.2.1(1), providing fasteners at all continuous panel edges are spaced in accordance with the boundary fastener spacing.
e. The minimum nominal depth of framing members shall be 3 inches nominal. The minimum nominal width of framing members not located at boundaries or adjoining panel edges shall be 2 inches.
f. Staples shall have a minimum crown width of 7/16 inch, and shall be installed with their crowns parallel to the long dimension of the framing members.
g. High load diaphragms shall be subject to special inspection in accordance with Section 1704.6.1.
h. For shear loads of normal or permanent load duration as defined by the AF & PA NDS, the values in the table above shall be multiplied by 0.63 or 0.56, respectively.

TABLE 2306.2.1(2)-continued-ALLOWABLE SHEAR (POUNDS PER FOOT) FOR WOOD STRUCTURAL PANEL BLOCKED DIAPHRAGMS UTILIZING MULTIPLE ROWS OF FASTENERS (HIGH LOAD DIAPHRAGMS) WITH FRAMING OF DOUGLAS FIR-LARCH OR SOUTHERN PINE FOR WIND OR SEISMIC LOADING

2306.2.2 Single diagonally sheathed lumber diaphragms. Single diagonally sheathed lumber diaphragms shall be designed and constructed in accordance with AF & PA SDPWS.

2306.2.3 Double diagonally sheathed lumber diaphragms. Double diagonally sheathed lumber diaphragms shall be designed and constructed in accordance with AF & PA SDPWS.

2306.2.4 Gypsum board diaphragm ceilings. Gypsum board diaphragm ceilings shall be in accordance with Section 2508.5.

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