Tech Today

Understanding fire ratings

Most roofing professionals understand the importance of providing fire-rated roof assemblies. However, what may not be well understood is what fire classifications are required and some of the nuances associated with such classifications.

Fire classifications

Roof assemblies' resistances to exterior fire exposure are typically tested and classified using two similar test methods: ASTM E108, "Standard Test Methods for Fire Tests of Roof Coverings," and UL 790, "Standard Test Methods for Fire Tests of Roof Coverings." The tests provide the basis for the Class A, B and C designations.

Class A designates resistance to relatively severe fire-test exposure; Class B designates resistance to relatively moderate fire-test exposure; and Class C designates resistance to relatively light fire-test exposure.