In classical times, a layer of sand was used to separate the structural substrate from the tile. This layer of sand would help to protect the tile from cracks in the substrate by allowing the tile to uncouple, or separate, from the substrate. In more modern times, a reinforced mortar bed has been used to provide a buffer between the substrate and tile. While effective, reinforced mortar beds can add inches of additional height to the floor installation. Today’s
uncoupling membranes are designed to provide a similar function by allowing the tile to move independently from the substrate but without the addition of extra height.
Uncoupling membranes come in roll, are lightweight, and easy to install. Composed of a thin sheet with a waffle-like grid or mesh on one side and an anchoring fleece or fabric attached on the underside, uncoupling membranes are ideal for protecting all types of floor tile. They can be installed on a wide range of flooring substrates including concrete, cement mortar, cement backerboard, and plywood. Furthermore, uncoupling membranes can often be installed over challenging substrates like green concrete.
In addition to providing excellent crack suppression, uncoupling membranes will typically provide vapor management properties. By allowing vapor to dissipate through channels beneath the membrane, moisture buildup below the substrate can be prevented. This becomes especially important with substrates that require a lengthy curing time. Waterproofing can also be achieved when the seams of the installed uncoupling membrane are joined together with an appropriate tape, as recommended by the manufacturer.
To install the uncoupling membrane, the fabric underside is attached to the flooring substrate with either a modified or unmodified thinset, depending on the substrate. "Peel & Stick" uncoupling membranes are also available on the market today. Next, a coat of mortar is applied over the grid, making sure all the depressions or cutaways are completely filled. With a final coat of thinset combed over the top, the tile can then be laid.