Ceramic tiles have one very human quality: Sometimes they crack under pressure. And although the installer for many years been seeking ways to strengthen the bond between tiles and their subfloors, often caused by stress fractures that are too close bond. When changes in temperature and humidity cause the subfloor to expand or contract, tile and grout can crack or buckle.

Schluter-Systems (www.schluter.com) has one solution: a polyethylene membrane in a pattern wafflelike placed between the subfloor and tile. Called Ditra, it is eight inches thick and weighs 2 ounces per square foot. Ditra acts as a mild "uncoupling membrane" that frees the surface of the tiles from the subfloor pressure. This also serves as a layer Waterproofing. Ditra works on commonly used subfloor materials, including plywood and concrete.

Ditra has been used commercially for almost 20 years, and has developed more into the housing market with increasing improvement projects home, including the do-it-yourselfers, according to Reinhard Plank, president of Schluter-Systems North America.