agreed, but if we are talking about a hearth extension that whose main purpose is for embers shooting out, any substrate does not get very hot at all in front of the stove in a extended hearth scenario, the finish material, yes, it gets warm, pretty warm. when my stove is 600d and i feel the floor in front, it's only warm.
any other application, i agree that durock is the safe choice.
any other application, i agree that durock is the safe choice.