Schluter Systems Ditra 150-sq ft Polyethylene Waterproofing Tile MembraneDitra is an uncoupling membrane designed for ceramic, porcelain, and stone tile installations on floors. It provides uncoupling to prevent cracked tile and grout. It is made of polyethylene creating a waterproofing layer protecting the substrate. Ditra can be installed over a variety of subfloors including concrete, plywood, OSB and radiant heated floors. The thickness of the tile assembly is minimized by using Ditra, which is only 1 8 in thick.