As 2 hours of fire protection has become the standard for fire safety in America, it has become somewhat of a standard practice to include two layers of type X drywall within a building's perimeter in order to achieve this required level of fire safety.
Spread rate: Spread rate will depend on the measure of fire protection desired. Example: Thickness 3/16" inch= 30 min.,3/8" inch=1 hour, 1/2" inch = 2 hour resistance.
To earn this rating, the wall panel or materials the wall is made out of need to be rigorously tested to demonstrate their fire resistance and ability to maintain structural integrity during direct exposure to flames. A 2-hour fire-rated wall must have a minimum thickness of 5 inches.
1-hour fire-rated wall: Apply two layers of ⅝" Type X gypsum secured with a layer of setting-type joint compound between them.
Regular 5/8" gyp board only gives 30 minutes of rating while gypsum type X can give 1 hour. Intumescent paint can upgrade the structure to 2-hour rating. Products based on intumescent paint can typically be applied to steel, sheet material, sheetrock, composite panels, and interior woods.
As 2 hours of fire protection has become the standard for fire safety in America, it has become somewhat of a standard practice to include two layers of type X drywall within a building's perimeter in order to achieve this required level of fire safety.
Specifically, 1" thick shaftliner panels that qualify as Type X provide a 2-hour fire rating when installed in a double-layer, non-load bearing H-stud Area Separation Wall assembly. All gypsum shaftliner panels on the market meet this definition, so this article will focus only on 1/2" and 5/8" thick products.
A 1-hour fire-rated wall can resist the passage of flames and high temperatures for a minimum of one hour, providing a basic level of protection. 2-hour fire-rated walls, on the other hand, offer a higher degree of resistance, as they are designed to withstand fire exposure for a minimum of two hours.
By the time you get into level 3, you're dealing with a relatively standard interior drywall finish. This level is meant to be textured and painted. Typically, level 3 drywall is covered in a medium to heavily textured finish to hide any imperfections.
The fire-resistance rating of concrete masonry walls depends on the type of aggregate used in the units. A 2-hour rating can be achieved by a wall with an equivalent thickness of as little as 3 1/5 inches when expanded slag or pumice is used or 4 1/2 inches when siliceous gravel is used as the aggregate.
The hour ratings for fire dampers must be 75% of the hour rating for the wall, floor or partition. That is why a fire damper rated for 1.5 hours can be used in a fire barrier rated for up to 2 hours and a fire damper rated for 3 hours can be used in a fire barrier rated up to four hours.
While drywall remains a widely used fire protection material, DC315 fire-retardant paint offers several advantages, particularly when applied over spray foam insulation. Its cost-effectiveness, seamless application, lighter weight, and superior performance in irregular spaces make it a better alternative to drywall.
The two layers of 1" gypsum shaft liner provides the 2 hour rating, and maintaining the 4" air gap is as important as the 2 hour rated wall (National Gypsum's representative says the shaft liner and the " air gap is the "rated assembly".)
US110 Fire Barrier Foam - Commercial Fire Block Foam 2 Hour Fire Rated - IFTI.
So, while it is a common industry assumption that Type C panels are required in ceilings and Type X panels for walls, the use in any given application is not limited by panel type, so long as the panel has been evaluated and approved for such use.
Typically, one layer of 5/8” type X fire rated drywall is good for 30 minutes, so a wall with said drywall on both sides is a one hour wall, two layers on each side is a 2 hour wall, etc.
In a compartment wall that separates buildings, the fire door must match the fire resistance period of the wall containing the door with a minimum period of 60 minutes. In all other situations, a 30 minute fire door (FD30) is allowed.
Types of Fire-Rated Drywall
It's typically installed in spaces that are the most likely to catch fire, such as kitchens and boiler rooms. At ⅝ of an inch thick, it's also thicker than standard drywall.
A Level 5 drywall finish involves an additional skim coat of joint compound over the entire surface, providing the highest-quality finish. This level is essential for areas with critical lighting conditions, where the appearance of the wall is paramount. It can deliver a smooth, uniform surface.
3/8-Inch Drywall: Just slightly thicker than 1/4-inch drywall, 3/8-inch drywall is also a good choice for curved walls. This thickness is most often used to repair existing drywall that needs patching.
Hides uneven studs – Hanging horizontally also allows the drywall to flow over the framing so that bowed studs create less of a problem. If the drywall were hung vertically and a seam placed on a bowed out stud, the seam would be magnified because of the bump in the wall.
Gold Bond® XP® Fire-Shield® Radius Gypsum Board is 5/16” thick and consists of a high density, fire-resistant gypsum core encased in a heavy, abrasion- and mold-, mildew- and moisture-resistant PURPLE® paper. Used in the construction of multi-layered, fire-rated wall assemblies.
Fire/smoke dampers are typically rated for 1-1⁄2 or 3 hours fire resistance. A 1-1⁄2 hour rated damper is sufficient for walls or floors having a rating of less than 3 hours. If the wall or floor has a rating of 3 hours or more, a 3 hour rated damper is required for sufficient protection.
Areas that experience high moisture levels or excessive humidity due to appliances, fixtures, or environmental conditions can benefit from mold-resistant drywall. Consider using mold-resistant drywall in kitchens, bathrooms, laundry rooms, mudrooms, and similar spaces where moisture is constantly present.