When you embark on a drywall installation project, building codes frequently dictate the specific drywall types to be used. One of the drywall types specified in building codes is Type X or Type C, commonly referred to as fire-rated drywall.
Despite its benefits, fire-rated drywall is sometimes credited with more qualities than it truly possesses. While it is fire-rated, it should not be confused with being fireproof. It can slow down the spread of fire but cannot completely halt it. Type X and Type C drywall are just one of several safety measures homeowners should adopt in the event of a house fire. It’s essential to note that fire ratings for Type X and Type C drywall refer to the entire wall system, not just the drywall itself.
Fire-Rated Type X or C Drywall
Fire-rated drywall is thicker than standard sheets and may include additional additives in the gypsum core, such as fiberglass. Its primary purpose is to delay the advancement of a fire, allowing occupants more time to evacuate.
What is Fire-Rated Type X Drywall?
Commonly known as Type X drywall, fireproof drywall has a thickness of 5/8 inches, including all layers.
It incorporates glass fibers into the board to enhance its fire resistance, and its denser composition compared to standard gypsum and paper drywall makes it more resistant to fire degradation.
Most Type X drywall has a one-hour fire rating, whereas the 1/2-inch drywall used elsewhere in the house offers a 30-minute fire rating. Additionally, Type X drywall provides slight sound absorption and greater strength compared to typical 3/8-inch or 1/2-inch drywall.
Type X vs. Type C Drywall
Both Type X and Type C drywall are classified as fire-resistant materials and have a 60-minute wall system rating.
Type C drywall contains more additives in its gypsum core, enhancing its fire resistance beyond that of Type X drywall.
Why Fireproof Drywall is Fire-Rated
Type X and Type C drywall are not entirely fireproof but are designed to withstand flames longer than regular drywall.
It’s important to note that covering an area with Type X or Type C drywall does not guarantee fire safety for that area, as fires can find alternative pathways through vents, doors, gaps, cracks, and unsealed stud wall assemblies.
The additional 1/8-inch thickness in Type X and Type C drywall, along with their other properties, doubles the fire safety margin to 60 minutes compared to the 30 minutes of regular 1/2-inch drywall. This is why fire-rated drywall is sometimes referred to as one-hour fire wallboard.
Fire-Rated Drywall
- Referred to as Type X or Type C
- Thickness of 5/8 inches
- Fire resistance rating of 60 minutes
- Includes embedded glass fibers
- Required by many building codes
- Rating based on complete assembly systems, not the drywall alone
Where to Install Type X or C Drywall
In residential settings, building codes often mandate the installation of fire-rated drywall in specific locations, including:
- Near furnace and utility rooms
- Spaces with wood stoves
- Garages, particularly the walls separating the garage from the main house
- Garage ceilings in areas with living spaces above them
Should You Install Type X or C Drywall Everywhere?
It is not necessary to install fire-rated drywall throughout the entire home.
Fire-rated drywall typically costs 20% more than standard drywall panels, which, while not significant for small projects, can result in a substantial cost difference when used extensively in a home.
Moreover, fire can find easier paths to spread than through drywall. For instance, if you were to install Type X or Type C drywall in areas like bathrooms, nurseries, bedrooms, or home offices, fire could readily pass through open doors with oxygen-rich air and hollow-core doors before attempting to burn through the drywall.
If you wish to have fire-rated drywall installed throughout your house, you would need to request this from your contractor, as it is not typically standard practice.
Type X or C Drywall Testing Limitations
The effectiveness of Type X or Type C drywall is determined not only by the drywall sheet itself but also by the entire wall system, including components like studs and insulation.
Manufacturers, such as USG, emphasize that ASTM (American Society for Testing and Materials) testing of fire-rated drywall requires testing the entire “assembly/systems” rather than just the drywall itself. Because these assemblies consist of various parts, any of which could impact the results, the outcomes may be influenced. USG explains:
Thickness and Composition
Conventional drywall is available in thicknesses of 1/4-inch, 3/8-inch, and 1/2-inch. In contrast, Type X and Type C fire-rated drywall has a thickness of 5/8 inches.
In addition to the standard gypsum found in regular drywall, fire-rated drywall includes glass fibers that form a more robust core. The gypsum and fiberglass are tightly packed in Type X and Type C drywall compared to regular drywall.
Cost and Availability
Fire-rated drywall is more expensive than standard drywall, typically costing 10% to 20% more than conventional drywall of comparable thickness.
Type X and Type C fire-rated drywall are readily available at local home improvement stores and contractors’ supply houses.
tag: # Basics of Fire-Rated Type X or C Drywall
