I just added a 20' x 14' screened porch to my house. It was built on a full foundation giving me new storage space in the basement. The builders put 3/4" plywood as a subfloor, then laid down a Grace Water and Ice membrane to make it watertight. The problem is that they had planned to lay Home Depot's Allure Ulltra vinyl tiles as a floating, waterproof floor. Perfect, right? Nope! It looke awesome but it is not rated for exterior use. I am looking for a waterproof, floating, exterior flooring option and am stuck! The other little glitch is that the 36" walls are raised about 2" from the floor, to allow for ventilation. Do you have any suggestions? Is "luxury vinyl tile" rated for exterior use? Help!!!