The following words and terms shall, for the purposes of this chapter and as used elsewhere in this code, have the meanings shown herein.
CEMENT PLASTER. A mixture of portland or blended cement, portland cement or blended cement and hydrated lime, masonry cement or plastic cement and aggregate and other approved materials as specified in this code.
GYPSUM BOARD. Gypsum wallboard, gypsum sheathing, gypsum base for gypsum veneer plaster, exterior gypsum soffit board, predecorated gypsum board or water-resistant gypsum backing board complying with the standards listed in Tables 2506.2, 2507.2 and Chapter 35.
GYPSUM PLASTER. A mixture of calcined gypsum or calcined gypsum and lime and aggregate and other approved materials as specified in this code.
INTERIOR SURFACES. Surfaces other than weatherexposed surfaces.
- Ceilings and roof soffits enclosed by walls, fascia, bulkheads or beams that extend a minimum of 12 inches (305 mm) below such ceiling or roof soffits.
- Walls or portions of walls beneath an unenclosed roof area, where located a horizontal distance from an open exterior opening equal to at least twice the height of the opening.
- Ceiling and roof soffits located a minimum horizontal distance of 10 feet (3048 mm) from the outer edges of the ceiling or roof soffits.
GYPSUM BOARD MATERIALS AND ACCESSORIES
|Accessories for gypsum board||ASTM C 1047|
|Adhesives for fastening gypsum |
|ASTM C 557|
|Elastomeric joint sealants||ASTM C 920|
|Exterior soffit board||ASTM C 931|
|Fiber-reinforced gypsum panels||ASTM C 1278|
|Glass mat gypsum backing panel||ASTM C 1178|
|Glass mat gypsum panel||ASTM C 1658|
|Glass mat gypsum substrate||ASTM C 1177|
|Gypsum backing board and gypsum shaftliner board||ASTM C 442|
|Gypsum ceiling board||ASTM C 1395|
|Gypsum sheathing||ASTM C 79|
|Gypsum wallboard||ASTM C 36|
|Joint reinforcing tape and compound||ASTM C 474; C 475|
|Nails for gypsum boards||ASTM C 514, |
F 547, F 1667
|Predecorated gypsum board||ASTM C 960|
|Steel screws||ASTM C 954; C 1002|
|Steel studs, load-bearing||ASTM C 955|
|Steel studs, nonload-bearing||ASTM C 645|
|Standard specification for gypsum board||ASTM C 1396|
|Testing gypsum and gypsum products||ASTM C 22; C 472; |
|Water-resistant gypsum backing board||ASTM C 630|
LATH, PLASTERING MATERIALS AND ACCESSORIES
|Accessories for gypsum veneer base||ASTM C 1047|
|Blended cement||ASTM C 595|
|Exterior plaster bonding compounds||ASTM C 932|
|Gypsum base for veneer plasters||ASTM C 588|
|Gypsum casting and molding plaster||ASTM C 59|
|Gypsum Keene's cement||ASTM C 61|
|Gypsum lath||ASTM C 37|
|Gypsum plaster||ASTM C 28|
|Gypsum veneer plaster||ASTM C 587|
|Interior bonding compounds, gypsum||ASTM C 631|
|Lime plasters||ASTM C 5; C 206|
|Masonry cement||ASTM C 91|
|Metal lath||ASTM C 847|
|Sand||ASTM C 35; C 897|
|Perlite||ASTM C 35|
|Vermiculite||ASTM C 35|
|Plastic cement||ASTM C 1328|
|Portland cement||ASTM C 150|
|Steel screws||ASTM C 1002; C 954|
|Steel studs and track||ASTM C 645; C 955|
|Welded wire lath||ASTM C 933|
|Woven wire plaster base||ASTM C 1032|
Gypsum board and gypsum plaster construction shall be of the materials listed in Tables 2506.2 and 2507.2. These materials shall be assembled and installed in compliance with the appropriate standards listed in Tables 2508.1 and 2511.1.1, and Chapter 35.
Exception: Joint and fastener treatment need not be provided where any of the following conditions occur:
- Where the gypsum board is to receive a decorative finish such as wood paneling, battens, acoustical finishes or any similar application that would be equivalent to joint treatment.
- On single-layer systems where joints occur over wood framing members.
- Square edge or tongue-and-groove edge gypsum board (V-edge), gypsum backing board or gypsum sheathing.
- On multilayer systems where the joints of adjacent layers are offset from one to another.
- Assemblies tested without joint treatment.
Gypsum board shall be permitted to be used on wood joists to create a horizontal diaphragm ceiling in accordance with Table 2508.5.
SHEAR CAPACITY FOR HORIZONTAL WOOD FRAMED GYPSUM BOARD DIAPHRAGM CEILING ASSEMBLIES
|MATERIAL||THICKNESS OF MATERIAL |
|SPACING OF FRAMING MEMBERS |
|SHEAR VALUEa, b|
(plf of ceiling)
|MIMIMUM FASTENER SIZE|
|Gypsum board||1/2||16 o.c.||90||5d cooler or wallboard nail;|
|15/8-inch long; 0.086-inch shank;|
|15/64 inch headc|
|Gypsum board||1/2||24 o.c.||70||5d cooler or wallboard nail;|
|15/8-inch long; 0.086-inch shank;|
|15/64 inch headc|
For SI: 1 inch = 25.4 mm, 1 pound per linear foot = 14.59 N/m.
- Values are not cumulative with other horizontal diaphragm values and are for short-term loading due to wind or seismic loading.Values shall be reduced 25 percent for normal loading.
- Values shall be reduced 50 percent in Seismic Design Categories D, E and F.
- 11/4-inch, No. 6 Type S or W screws are permitted to be substituted for the listed nails.
Water-resistant gypsum backing board shall not be used in the following locations:
- Over a vapor retarder in shower or bathtub compartments.
- Where there will be direct exposure to water or in areas subject to continuous high humidity.
- On ceilings where frame spacing exceeds 12 inches (305 mm) o.c. for 1/2-inch-thick (12.7 mm) water-resistant gypsum backing board and more than 16 inches (406 mm) o.c. for 5/8-inch-thick (15.9 mm) water-resistant gypsum backing board.
Water-resistive barriers shall be installed as required in Section 1404.2 and, where applied over wood-based sheathing, shall include a water-resistive vapor-permeable barrier with a performance at least equivalent to two layers of Grade D paper.
Exception: Where the water-resistive barrier that is applied over wood-based sheathing has a water resistance equal to or greater than that of 60-minute Grade D paper and is separated from the stucco by an intervening, substantially nonwater-absorbing layer or drainage space.
Plastering gypsum plaster or cement plaster shall not be less than three coats where applied over metal lath or wire fabric lath and not less than two coats where applied over other bases permitted by this chapter.
Installation of lathing and plaster materials shall conform with Table 2511.1.1 and Section 2507.
First and second coats of cement plaster shall be applied and moist cured as set forth in ASTM C 926 and Table 2512.6.
|COAT||MINIMUM PERIOD MOIST |
|MINIMUM INTERVAL |
|First||48 hoursa||48 hoursb|
|Second||48 hours||7 daysc|
- The first two coats shall be as required for the first coats of exterior plaster, except that the moist-curing time period between the first and second coats shall not be less than 24 hours. Moist curing shall not be required where job and weather conditions are favorable to the retention of moisture in the cement plaster for the required time period.
- Twenty-four-hour minimum interval between coats of interior cement plaster. For alternate method of application, see Section 2512.8.
- Finish coat plaster is permitted to be applied to interior cement plaster base coats after a 48-hour period.