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Materials & Specificationsaka: FRRaka: fire ratingaka: hourly rating

Fire Resistance Rating

In Plain English

A rating measuring how long a wall or floor can withstand fire, expressed in hours.

Definition

Fire resistance rating is the time period in hours that a building assembly can withstand fire exposure as determined by standardized testing procedures. Common ratings are 1-hour, 2-hour, and 3-hour. Building codes specify required fire resistance ratings based on building occupancy, height, area, and construction type.

Why It Matters in Bidding

The required fire resistance rating dictates which wall, floor, and structural assemblies a project must use, and those assemblies carry very different material and labor costs, so misreading the rating during takeoff can leave a bid short on entire trades. Estimators must trace code-mandated ratings through the drawings to price the correct gypsum layers, fireproofing, or rated framing rather than a cheaper non-rated alternative.

Example

Reading the life-safety plan, the estimator prices a 2-hour rated stair enclosure with two layers of fire-rated gypsum each side instead of the single-layer partition used elsewhere in the building.

Related Terms

Fire-Rated AssemblyDrywallBuilding CodeSpecifications Document

Frequently Asked Questions

Ratings come from standardized furnace testing of full assemblies, where a specimen is exposed to controlled fire and measured for how long it resists structural failure and heat transmission. The resulting listed hourly rating applies only when the assembly is built with the exact tested materials, thicknesses, and fastening.
Building codes set required ratings based on occupancy type, building height and area, construction type, and the function of the element, such as exit enclosures or occupancy separations. The architect specifies these on life-safety and assembly schedules, which the estimator must follow to price the correct rated systems.
Generally yes, because higher ratings require added gypsum layers, thicker assemblies, applied fireproofing, or more robust structural protection, all of which increase material and labor. Estimators should map every rated location during takeoff so the bid captures the cost difference rather than carrying everything as standard partitions.

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