We have a covered deck that has an enclosed storage room underneath. We are extending this deck 8' and raising up a lower deck (that is not covered and has no storage underneath). The finished deck will be 17'x20'. Currently I have a vinyl decking on the covered portion (so moisture can't leak through) and composite decking on the un-covered portion. Once the deck has been expanded, I want the entire floor to be covered in the same material. Any suggestions for something that will not leak through to the room below without going back to a vinyl type of product?