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
+1 to the previous comments. Depends on what the foam manufacturer specifies as well as what the exterior sheathing is going to be. I would also recommend a thicker foam for additional insulation and ... read more