What is the difference between fire retardant and fire resistance?
A fire retardant material slows burning across the surface of a combustible substrate. A fire resistive material delays heat penetration through a substrate. Q. Fire resistance – what is an “hourly rating” and does it compare to flame spread? A fire-resistive rating is the time that exterior wall construction can withstand fire exposure as determined by a standard fire test. Wall construction can be classified as 4-hour, 3-hour, 2-hour, 1-hour and non-rated construction. This rating is determined by a different test, known as “Standard Methods of Fire Tests of Building Construction and Materials” NFPA No. 251, ASTM E 119, UL No. 263). The test exposes an assembly to heat and flame on one side and tests for heat transmission, burn-through, structural integrity and ability to withstand a hose stream from a fire hose. Hourly Ratings are assigned only to complete assemblies, of structural materials for buildings, (wall, floor, door, ceiling, roof, etc.) and generally require use of a nonco
