Rigid Supporting Surface UL 962A:2023 Clause 38

For the impact tests, the rigid supporting surface is to consist of a layer of nominal 25 mm (1 in) tongue-and-groove oak flooring (actual size18 by57 mm or 3/4 by 2-1/4 in mounted on two layers of nominal 19 mm (3/4 in) plywood. The assembly is to rest on a concrete floor or an equivalent nonresilient floor during the test. The rigid backing surface is to consist of 19 mm (3/4 in) plywood over a rigid surface of concrete. An equivalent nonresilient backing surface may be used.

UL 962A:2023 Clause 38.1.5