This excellent product is made up of two layers . Its purpose is to uncouple the stone floor from stresses arising from the subfloor which can otherwise lead to cracking in the tiles. For example- where tiles are laid on electric underfloor heating on a plywood base - the heat typically shrinks the ply , the adhesive will not cope with this and the tile will crack . Similarly new screeds , especially heated screeds are prone to cracking and slight curling in the long run - again this often leads to cracking. Durabase matting will prevent this and we strongly recommend its use on all new screeds , all timber subfloors and anywhere where you have subfloors of a mixed composition.