Hard to tell for sure without a close look, but the roofing / waterproofing material looks like TPO, a single-ply roofing membrance. It is not made for direct traffic, so appears someone has installe ... read more
John,
I must confess to never having seen that application.
I am not sure the finish would look good or even hold up over the long term. I would also be worried about the potential vapor retarder ... read more