Fire Rated Drywall Guide: Type X, Type C, and 5/8 Fire-Rated Options
Fire rated drywall is a code requirement in many residential and commercial applications, from attached garage walls to apartment corridor partitions. Type C drywall is the highest-performance standard product available for fire-rated assemblies, outperforming standard Type X through a proprietary glass fiber and chemical additive system. The term fireproof drywall is technically a misnomer since no gypsum product is truly fireproof, but Type X and Type C panels significantly delay flame and heat transmission through a wall assembly. The 5/8 fire rated drywall product is the most commonly specified panel for one-hour fire-rated residential assemblies. Understanding when 1/2 type x drywall is permitted versus when 5/8 product is required keeps your project code-compliant and prevents failed inspections.
This guide covers each product type, the assemblies they belong in, and the installation details that make or break fire ratings.
Type X versus Type C drywall
Type X construction and ratings
Type X fire rated drywall contains glass fibers dispersed through a denser gypsum core. The glass fibers prevent the core from crumbling when heat causes the gypsum to release its chemically bound water and begin to calcine. A single layer of 5/8 fire rated drywall Type X on each side of a standard wood stud wall achieves a one-hour fire rating in UL-listed assemblies. The 1/2 type x drywall uses the same additive chemistry but in a thinner core, achieving 45-minute ratings in some listed assemblies. Most residential codes specify 5/8 inch Type X in attached garage separations.
Type C performance advantages
Type C drywall uses a higher glass fiber content and adds vermiculite or other refractory additives to the core. When exposed to fire, the Type C core expands slightly rather than contracting as standard gypsum does. This expansion keeps the panel in contact with its framing longer, extending the fire barrier duration. Two layers of Type C drywall often achieve two-hour fire ratings in configurations where two layers of standard Type X achieve only one hour. Type C products cost 15 to 30 percent more than Type X but are required in certain commercial high-rise applications and multi-family corridors.
5/8 fire rated drywall: the residential standard
The 5/8 fire rated drywall panel is the default product for one-hour fire-rated assemblies in the International Residential Code. It belongs on the garage side of the wall and ceiling assembly between an attached garage and living spaces. IBC Section R302.6 requires a half-inch drywall minimum on the garage side and 5/8 Type X if the garage has a habitable room above. Check your local jurisdiction for any amendments that increase these minimums. In multi-family construction, 5/8 fire rated drywall appears in dwelling unit separations, corridor walls, and mechanical shaft enclosures.
Installation requirements for fire-rated assemblies
Fastening and joint treatment
Fire-rated assemblies must be installed exactly as described in the UL or GA file for the assembly. Screw spacing, panel orientation (horizontal or vertical), and joint treatment all affect the rated performance. Blocking at panel edges is required in some listed assemblies. The assembly file specifies the joint compound type and number of coats. Using a non-listed compound or omitting the tape coat can void the fire rating even if the product itself is correct.
Penetrations and continuity
Every penetration through fire rated drywall must be sealed with a listed firestop product. Electrical boxes, pipe penetrations, and HVAC ducts all require listed firestop collars or sealants to maintain the assembly’s rated continuity. An unsealed penetration in a one-hour wall reduces the effective resistance at that location to near zero. Firestop installation is commonly inspected before wall closure.
Key takeaways: Use 5/8 fire rated drywall Type X for standard one-hour residential assemblies. Specify Type C when two-hour ratings or superior performance are required. Follow the UL assembly file exactly, and firestop every penetration to maintain the rated system.
