I intend to place a hearth on to the plywood floor of my mobile home. Just a basic question really. Do I need a plastic barrier between the plywood and the concrete? My worry is that it may condensate under the concrete if I put plastic. Any thoughts?
I can't think of a strong reason to put polyethylene sheeting down, but if you want to preserve the plywood surface for the future, or you're afraid that water will leak through the seams, you could. I'd be a bit concerned that poly would act as a lubricant and allow more movement than is desired.
Condensation isn't really a concern with such a small, interior area unless you expect temperatures above and below to be dramatically different.