Uncoupling / Decoupling membrane is a barrier placed between the tiles and the substrate ensuring that any movement or cracks are isolated and do not transfer through to the tiles. These anti-crack mats will also provide a 100% waterproof barrier. Suitable for: --- Wood Or Concrete Floors --- Wetrooms or Commercial Areas --- Underfloor heating --- Ceramic, Porcelain, Stone or Mosaic Tiles Why Use A Waterproof Decoupling Membrane: Building materials expand and contract with changes in temperature. These materials vary in how much they move and sometimes these differences create crack or stresses that can be disastrous to tiled above and cause it to expand the substrate which can then lead to cracks in tiles and grout joints, or even cause tiles to de-bond.