“It is critical to close in and condition the interior areas before installing and finishing paper faced gypsum board,” says Deborah Callaway, Manager, Technical Services, PABCO Gypsum.
If not, you may experience the following issues: nail or screw pops, mold or mildew, board sagging, cracks or ridging along joints, cracking along edges of finishing tape, too short or too long drying times, or too little or too much shrinkage.
Specifications for the Interior Conditions
ASTM and the Gypsum Association (GA) specify the interior environmental conditions for proper installation of gypsum board. Prior to installation, the gypsum board must be protected from the following:
- Dirt and debris
- Direct exposure to rain, snow, or excessive sunlight
- Direct exposure to water or continuous high humidity
- Sustained exposure to temperatures above 125° F for extended periods of time
Framing materials should also be protected, particularly wood products, as they will absorb and release moisture until it has reached an equilibrium with the surroundings. Wood products must be kept dry at all stages of construction so that the moisture content is less than 19%, as defined by the model building codes. The minimum moisture content can be as low as 6%, depending on the region.
When the moisture content is greater than that of the surrounding environment, it will “dry out” by releasing moisture to reach equilibrium and the lumber products will shrink. As this happens, the fastener will be pulled with the wood, causing an indent into the drywall called “pops”. If the lumber is drier than that of the surrounding environment, it will “moisten” by absorbing moisture to reach equilibrium and swell. As this happens, ridges can form along the joints.
Follow the Guidelines
To decrease the chances of any of the above-mentioned issues, follow the guidelines specified in ASTM C840 Standard Specification for Application and Finishing of Gypsum Board, or GA-216 Application and Finishing of Panel Products. For proper finishing of installed drywall, refer to GA-214 Recommended Levels of Board Finish.
To summarize, when you begin installation of paper faced gypsum board, the interior should be fully enclosed and protected from outside elements. Once enclosed, the interior needs to be conditioned and maintained at a minimum 50° F, ideally until the building is occupied. If a temporary heat source is used, the temperature should be kept below 95° F and adequate ventilation needs to be provided to allow any humidity to escape.
Corrections and remedies are also available from the GA and other industry associations, or PABCO® Technical Services, techservice@PABCOgypsum.com, 866-282-9298.