Clause 18.104.22.168 The material has a structural base of a noncombustible material with a surfacing not exceeding a thickness of 1/8 in. (3.2 mm) where the surfacing exhibits a flame spread index not greater than 50 when tested in accordance with ASTM E 84, Standard Test Method for Surface Burning Characteristics of Building Materials or ANSI/UL 723, Standard for Test for Surface Burning Characteristics of Building Materials. [5000:22.214.171.124.1]
Question regarding the meaning of the words, Structural base of noncombustible material:
- Does this mean materials used for structure (such as; steel, concrete or other materials which is used for building structure) with above mentioned surface?
- Or, this means whatever base materials, (ex.; soft rock wool), which is noncombustible under the surface of not over 1/8” thickness?