Gypsum board and gypsum panel products shall be permitted on wood joists to create a horizontal diaphragm in accordance with Table R702.3.6. Gypsum board and gypsum panel products shall be installed perpendicular to ceiling framing members. End joints of adjacent courses of board and panels shall not occur on the same joist. The maximum allowable diaphragm proportions shall be 11/2:1 between shear resisting elements. Rotation or cantilever conditions shall not be permitted. Gypsum board or gypsum panel products shall not be used in diaphragm ceilings to resist lateral forces imposed by masonry or concrete construction. Perimeter edges shall be blocked using wood members not less than 2-inch by 6-inch (51 mm by 152 mm) nominal dimension. Blocking material shall be installed flat over the top plate of the wall to provide a nailing surface not less than 2 inches (51 mm) in width for the attachment of the gypsum board or gypsum panel product.
SHEAR CAPACITY FOR HORIZONTAL WOOD-FRAMED GYPSUM BOARD DIAPHRAGM CEILING ASSEMBLIES
| MATERIAL | THICKNESS OF MATERIAL (min.) (inch) | SPACING OF FRAMING MEMBERS (max.) (inch) | SHEAR VALUEa, b (plf of ceiling) | MINIMUM FASTENER SIZEc, d |
| Gypsum board or gypsum panel product | 1/2 | 16 o.c. | 90 | 5d cooler or wallboard nail; 15/8-inch long; 0.086-inch shank; 15/64-inch head |
| Gypsum board or gypsum panel product | 1/2 | 24 o.c. | 70 | 5d cooler or wallboard nail; 15/8-inch long; 0.086-inch shank; 15/64-inch head |
For SI: 1 inch = 25.4 mm, 1 pound per linear foot = 1.488 kg/m.
- Values are not cumulative with other horizontal diaphragm values and are for short-term loading caused by wind or seismic loading. Values shall be reduced 25 percent for normal loading.
- Values shall be reduced 50 percent in Seismic Design Categories D0, D1, D2 and E.
- 11/4-inch, No. 6 Type S or W screws shall be permitted to be substituted for the listed nails.
- Fasteners shall be spaced not more than 7 inches on center at all supports, including perimeter blocking, and not less than 3/8 inch from the edges and ends of the gypsum board.