Ditra is a polyethylene uncoupling underlayment with a grid Ditra is an uncoupling membrane designed for ceramic 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.