Around 1960, the new tile laying technique employing thin-set mortar became widely used. The screed was now bonded directly to the concrete substrate. Once the screed had hardened, the tiles were laid using dry-set mortar. The former sandwich structure, built-up in four layers, was thus replaced by a monolithic structure. However, the new process failed to take into account the differences in physical behaviour of each of the layers, particularly the difference in dimensional changes between concrete/screed on the one hand and ceramic tiles on the other. Problems were created by shrinkage, warpage and cracking of the screed, the creation of temperature gradients caused by the installation of radiant heat systems, and floating screeds introduced for acoustic and thermal insulation. Schluter Systems GmbH has developed special systems to address these problems, namely Schluter-Ditra, a polyethylene membrane which compensates for dimensional changes between the screed and the floor tiles, and Schluter-Bekotec, a studded screed panel which eliminates warpage and cracking where there are radiant heat systems. Flooring assemblies that integrate insulation and radiant heat are emerging as major markets of the future.