Mold and Moisture Resistant Drywall

This Common Product (CP) covers mold-resistant drywall intended for interior walls and ceilings in areas that have periodic elevated humidity. Examples include bathrooms, kitchens, laundry rooms, and utility closets. These products are not, however, intended for use in areas that are continuously wet such as in saunas or as tile backer for showers or tubs. Mold-resistant drywall typically has a gypsum core sandwiched between recycled paper that has been treated with a biocide. In addition to the treated paper, wax or silicones are added to the gypsum core to make it more moisture-resistant. Some products add a biocide to the core to increase mold resistance as well. Standard mold-resistant drywall panels are 1/2", and most also come in a 5/8" type X option. The latter includes typical additives, like fiberglass and vermiculite, found in type X drywall to increase panel strength and fire resistance. Many mold-resistant drywall specialty products are also available, such as 1/2" Type C panels, and high impact or high abuse panels. Such products likely contain additional additives not identified in this CP, which covers standard 1/2" panels. Some mold-resistant drywall products are wrapped in a fiberglass mat instead of treated paper. These products may be used in exterior applications before the bulding envelope is enclosed and are out of the scope of this CP. This CP addresses drywall made with flue-gas desulphurization (FGD) gypsum. There are not significant differences in the composition of finished drywall products made using different gypsum sources, but natural gypsum is preferred over FGD gypsum because the FGD drywall production process can release mercury into the environment.