Can epoxy based flooring be installed over plywood flooring?

Answer 1

In a word, no.

In may words: Yes, it can, but you must understand what epoxy-based flooring actually is. If you are referring to products typically used to coat concrete garage floors, epoxy-based flooring is essentially a very resilient, thick paint (but actually not very thick at all compared to vinyl-sheet flooring or hardwood boards). Because it resists chemical staining and things like scuffing, it is ideal for a quick cosmetic improvement on hard surfaces like concrete. Concrete doesn't shift very much from temperature and moisture changes, so despite an occasional crack wherever the concrete cracks, epoxy stays where it is put when applied over concrete, if applied properly.

Plywood, on the other hand, shift dramatically due to temperature and moisture changes. Even if it is impervious to moisture from above, say if vinyl is placed over it, it will absorb moisture from underneath and on the sides. Nothing can be practically done to prevent wood from seasonal shifting. With that in mind, no matter how thick epoxy is applied to a large plywood subsurface, within a year as the seasons change, every sheet of plywood will become visible and the epoxy will crack at each seam. As general rule, one shouldn't apply a hard surface to a soft (wood surface).

If you are trying to cover a plywood floor inexpensively, your best options are vinyl-sheet flooring (sometimes incorrectly referred to as "linoleum"), carpet, or maybe even vinyl tiles. If you are determined to use some type of painting solution, just use acrylic-latex paint designed for outdoor decks, which are widely available at home improvement stores. It will be less expensive and will be able to shift with the seasonal changes in the wood, and also cover the grain of the wood in a more aesthetically pleasing manner. Good luck.