They may look just like regular drywall, but these panels are even more effective a barrier against fire than regular drywall. Fire resistant drywall is a specialized product having a gypsum core containing glass fibers and other non-combustible materials. The fibers act as reinforcement as well, helping to keep the board from disintegrating as easily as regular drywall.
This type of wallboard is designated Type X by the industry material spec ASTM C 36. According to the ASTM specifications, Type X drywall must present: at least 60 minutes of fire resistance for 5/8″ board or 45 minutes fire resistance rating for 1/2″ board, and 120 minutes for ¾ inch drywall, when installed single layer, and nailed on each face of load-bearing wood framing members. The installation is tested to the requirements of ASTM E 119, Methods of Fire Test of Building Constructions and Materials.
The most commonly used thickness is the 5/8 inch fire-resistant wallboard panels. It is available in 8 foot, 10 foot and 12 foot lengths and has a maximum approved framing spacing of 24 inches on center stud to stud.
Other than the Type X rating stamp on it, the only difference apparent to the user will be the more difficulty you will have in cutting it, compared to regular drywall, which is due to the toughness of the gypsum core.
Building codes typically call for the use of fire resistant drywall as firewalls in furnace or utility rooms, attached garages, and ceilings and walls that separate units in condominiums and apartment buildings. Because fire ratings depend on the complete installation, i.e., wallboard, studs, nailing pattern, etc, they are based on the assembly configuration.
The best reference guide for selecting the appropriate configuration for building code compliance is the Underwriters Laboratories manual. If you have questions, then call your local building inspector official or fire marshal, as they are the final arbiters.
- Underwriters Laboratories (UL) Fire Resistance Directory
- Intertek Testing Services’ Directory of Listed Products
- Gypsum Association’s Fire Resistance Design Manual