How Thick of Drywall Is a 15-Minute Fire Barrier?


A wall or ceiling serving as a fire barrier prevents the transfer of heat that would cause the combustion of materials on the other side of the barrier. The length of time the material prevents the spread of the flames is stated as the fire rating. The standard thickness of 1/2 inch sheetrock exceeds that of a 15-minute fire barrier as it is rated at 30 minutes. This sheetrock provides fire barrier protection for 30 minutes allowing building occupants to notify fire fighters, attempt to extinguish the fire or evacuate the building. Fire barriers are required by building codes in many areas especially around furnace or utility rooms.

Standard Drywall

  • Standard 5/8- or 1/2-inch drywall has a fire rating of 30 minutes when installed on both sides of a 2-by-4-framed wall.. This means that temperatures on the other side of the wall remain less than 250 degrees hotter than on the fire side of the drywall for at least 30 minutes after the fire ignites. This prevents the insulation or other building materials from bursting into flames.

Type X Drywall

  • Type X drywall is specially designed to serve as a fire barrier. Type X drywall increases the fire rating of 5/8-inch drywall to a minimum of 1 hour. Installing this material meets most building codes for fire barriers around furnace, utility rooms and between garages and entries into the home in residential buildings. It is commonly required for all drywall construction in commercial buildings.

Why Type X

  • Type X drywall uses fiberglass as a reinforcement for the gypsum. This creates a denser and heavier core of the drywall sheet. This maintains the integrity of the sheet during a fire which prevents the movement of the fire through cracks in the drywall. Type X also possesses better sound insulation qualities which prevents noise transference from room to room. However, Type X is commonly more expensive than standard drywall. Type C drywall is similar to Type X but contains a higher percentage of fiberglass and has longer fire ratings than Type X.

Other Considerations

  • The fire rating of the drywall is only part of the effectiveness of a fire barrier. Fire-rated doors are also necessary in the areas where fire barriers are required. Adequate smoke detectors and alarm systems alert people in time to control the fire before it penetrates through the walls.

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