Fire-rated drywall, also known as Type X or Type C drywall, is a special type of drywall designed to provide additional fire resistance and protection. It is composed of gypsum core layered between paper facers, just like regular drywall. However, Type X drywall contains glass fibers and other additives that help improve its fire-resistance rating.
Understanding the basics of fire-rated drywall can help you determine when and where to use it to meet specific fire protection requirements in a building. This article provides an in-depth overview of the composition, ratings, applications, installation, and maintenance considerations for Type X and Type C fire-rated drywall.
Composition of Fire-Rated Drywall
The core of Type X drywall is made from gypsum, like regular drywall. However, it contains additional materials such as:
- Glass fibers – Glass fibers are interspersed throughout the gypsum core. During exposure to high temperatures, the glass fibers reinforce the drywall and prevent it from cracking or falling apart. This provides added fire resistance.
- Vermiculite – Vermiculite is a mineral that expands when heated. The expanding vermiculite in the drywall core helps contain flames and hot gases.
- Additional binders – Extra binders may be added to the gypsum core to increase its strength and fire resistance.
The paper facers on fire-rated drywall also differ from regular drywall. They often contain glass fibers for extra strength and protection against heat and flames. Some Type X boards feature a foil facing on one side instead of paper. The foil improves radiant heat reflection.
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Fire Resistance Ratings
Fire-rated drywall is tested and classified based on its fire-resistance rating (FRR). This indicates the duration for which the drywall can contain a fire and prevent it from spreading.
Type X drywall typically provides a 1-hour or 2-hour FRR when tested in accordance with ASTM E119 standards. This means it can withstand a full-scale fire exposure for 1 or 2 hours before flames or excessive heat pass through. The exact FRR depends on the thickness and composition of the Type X board.
Type C drywall has a 3-hour FRR and provides even greater fire protection. It is typically thicker (up to 5/8” or 1/2″) and denser than 1-hour Type X boards.
The FRR and thickness should be marked clearly on the Type X or C drywall panels. Common sizes include:
- 1/2″ Type X – Typically 1-hour FRR
- 5/8″ Type X – Typically 1-hour or 2-hour FRR
- 1/2″ Type C – Typically 2-hour FRR
- 5/8″ Type C – Typically 3-hour FRR
The FRR of drywall indicates performance in standardized tests. Actual fire resistance depends on proper installation and construction details. Additional layers can provide longer protection.
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Applications and Uses
Fire-rated Type X and Type C drywall have a number of applications in both residential and commercial construction:
- Fire walls – Fire walls that compartmentalize buildings for safety require 1-hour or 2-hour FRR drywall.
- Fire barriers – Fire barriers divide sections of buildings vertically. Type X or Type C boards are used depending on the FRR required.
- Fire partitions – These walls divide horizontal sections of buildings. Appropriate FRR drywall should be installed.
- Shaft enclosures – Elevator shafts, stairwells, and other vertical openings need fire-rated drywall enclosures.
- Garages – The wall separating an attached garage from the home must be covered with drywall (often 5/8” Type X) with a 1-hour FRR.
- Furnace/water heater closets – These rooms with fuel-burning appliances require 1-hour FRR drywall separation.
- Commercial kitchens – The walls around commercial kitchens with cooking appliances call for 1-hour Type X protection.
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Using Type X or Type C drywall anywhere that building codes require a fire-resistance rating is essential for safety. The boards are also a smart enhancement for any fire-prone room.
Installation of Fire-Rated Drywall
Proper installation is crucial to achieve the full fire-resistance rating of Type X and Type C drywall. Here are some key installation guidelines:
- Use the correct type and thickness of drywall required for the assembly and FRR.
- Ensure the framing meets applicable building codes for fire-rated assemblies. This often includes closer stud spacing.
- Stagger joints between boards on opposite sides of partitions for improved integrity.
- Attach Type X drywall horizontally to wood or metal framing using screws spaced 8” apart in the field and edges. Ring-shank or bugle-head screws provide best performance.
- Use special fasteners approved for fire-rated construction. Nails should not be used.
- Seal joints between boards with fiber-reinforced joint compound. Tape and finish all joints.
- Seal all penetrations through the drywall with firestop putty or caulk to maintain fire resistance.
The gypsum board association provides detailed installation guides for Type X and Type C assemblies to achieve certified FRRs. Following best practices is key.
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Maintenance and Repairs
Proper maintenance is required to preserve the fire resistance of Type X and Type C drywall over time. Consider the following:
- Inspect for any cracks, gaps, or damage regularly and repair immediately with fire-rated joint compound and tape.
- Use only Type X or C panels matching the original specifications when patching or replacing damaged areas.
- Do not attempt to paint fire-rated drywall, as this may compromise performance. Leave it uncoated.
- Check firestops around penetrations to ensure they remain intact. Reapply firestop sealant if needed.
- Ensure insulation in wall cavities does not get compressed or displaced, as this can lower the assembly’s fire rating over time.
- Have fire-rated assemblies periodically inspected by a knowledgeable professional to verify fire resistance integrity.
With vigilance and proper repairs, fire-rated drywall can maintain its protective rating and function for the life of a building. Consult Gypsum Association guidelines for detailed maintenance recommendations.
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Cost Comparison
Fire-rated Type X and Type C drywall costs more than standard drywall but provides critical fire protection:
- Type X typically costs $1-$3 more per sheet compared to regular drywall.
- Type C boards can cost $4-$8 more per sheet than standard boards.
- Labor costs for installing fire-rated drywall are comparable to regular drywall.
- Total installed costs for Type X average $2-$5 per square foot compared to about $0.50-$2 for regular gypsum.
The extra cost for materials and labor is minor considering the added fire resistance and safety achieved. Where building codes require Type X or C drywall, the cost is a mandatory investment. In non-required areas, the small upgrade cost can provide peace of mind.
Key Takeaways and Summary
The major points to understand about fire-rated Type X and Type C drywall include:
- Special additives give Type X and Type C boards better fire resistance than regular drywall. Glass fibers and mineral reinforcement prevent cracking and contain flames.
- Ratings like 1-hour and 2-hour indicate the proven fire resistance time before failure when tested. Type C offers longest protection.
- Fire-rated drywall is required in many wall and ceiling assemblies by building codes. It is also smart for fire-prone rooms.
- Proper installation and maintenance is crucial to achieve the rated fire resistance over time. Damaged areas should be repaired promptly with Type X or C board.
- The small added cost for Type X or Type C is worth the significant boost in fire protection and safety achieved.
Understanding the enhanced composition, ratings, applications and installation techniques for fire-rated drywall allows it to serve its vital purpose in fire prevention. Architects, contractors and homeowners should become familiar with code requirements and best practices to leverage Type X and Type C board where needed. With this basic knowledge, fire-rated drywall can fulfill its role as a key fire protection component in both residential and commercial buildings.
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Frequently Asked Questions
Here are some common questions about fire-rated Type X and Type C drywall:
What is the main difference between Type X and regular drywall?
Type X drywall contains glass fibers and other additives that give it better fire resistance and higher fire ratings when tested. Regular drywall has a gypsum core only and no fire rating.
Should I use Type X or Type C in my home?
Type X is recommended for fire-rated wall and ceiling assemblies in homes as required by code. Type C provides even greater fire resistance for critical commercial separations.
Can I install fire-rated drywall myself?
Yes, Type X and Type C boards can be installed DIY-style like regular drywall. However, be sure to follow specific construction details to achieve the fire rating.
How do I patch damaged Type X drywall?
Damaged areas in Type X or Type C drywall should be repaired with patches of identical fire-rated board to maintain the original fire resistance.
Can I tile, wallpaper or paint over Type X drywall?
No. Fire-rated drywall should remain uncovered. Paint, wallpaper, or tiles may compromise the fire performance. Leave Type X and Type C boards bare.
How often should fire-rated assemblies be inspected?
It’s recommended to have a qualified professional inspect fire-rated drywall installations at least once a year to check for any damage or issues that could lower fire resistance over time.
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