Uncoupling Membranes for Tiling over Cement Slab

Uncoupling Membranes for Tiling over Cement Slabs Protect against Moisture and Shearing Force Problems that can Crack Tiles

By Mark J. Donovan




Ceramic, porcelain and stone tile floors look gorgeous and are easy to maintain and clean. However, they are susceptible to cracking if installed on an unstable subfloor, be it a wood subfloor or cement slab, without the use of an uncoupling membrane. Creating a solid wood subfloor is fairly easy to do, assuming correctly dimensioned floor joists were used in the subfloor construction, and proper thicknesses and layers of plywood are attached to them. Cement slabs is another matter. Cement slabs can crack and shift.

These shearing movements can cause tiles attached directly to the cement floor to crack and the grout to crumble. Moisture can also be a problem for tiles directly attached to cement slabs.

Fortunately there are easy to install uncoupling membranes for tiling over cement slabs to address these concerns.

One of the best uncoupling membrane products on the market is called DITRA. It was developed and is manufactured by Schluter Systems. DITRA is a Polyethylene inverted waffle looking membrane product that is attached directly to the cement slab with thinset mortar. The backside of the DITRA uncoupling membrane has a fleece like surface to ensure a solid bond to the thinset mortar.

The top layer of the DITRA uncoupling membrane has again an inverted waffle like appearance with a sea of individual square valleys for the thinset mortar to reside in and the tiles to attach to.

Uncoupling membrane for tiling floors

The valleys have slightly cutback bottom edges to help lock in the thinset mortar and to ensure a strong bond to the ceramic tile or stone.

The main purpose of using an uncoupling membrane for tiling over cement slab is to allow the ceramic tile to effectively float over the cement slab and uncouple it from any in-plane and shearing movements of the slab that can and will occur overtime. As a result, the ceramic tile will not crack or delaminate from the thinset mortar that it is attached to. Likewise the grout will not crack and crumble.

The DITRA Polyethylene uncoupling membrane also works to nearly eliminate moisture concerns. Cement slabs more often than not have ground moisture that percolates and wicks up through them. Ceramic, porcelain and stone tile, along with the thinset mortar can be negatively impacted from constant contact with high moisture levels. Over time this can cause the tiles to delaminate away from the cement slab.

Schluter’s DITRA Polyethylene uncoupling membrane product prevents moisture from reaching the tile and is specifically designed so that air channels on the back side of it can actually direct the moisture away from the tiled surface area.

Installing ceramic tile floor

So for your next cement slab tiling project make sure to take a look at uncoupling membrane products. Also, before installing the uncoupling membrane make sure you thoroughly clean the cement slab, repair any cracks in it, and if necessary apply a self leveling compound on it to create a flat surface. Also, if there is any underlying moisture or water issues associated with the slab have them resolved first prior to installing the tiles, even if you do plan on using an uncoupling membrane.


For information on installing a shower pan membrane liner for a ceramic tile shower, see the Shower Pan Membrane Liner Installation Ebook from HomeAdditionPlus.com.  The Shower Pan Membrane Liner EBook will quickly teach you the step-by-step process for installing the shower pan membrane liner correctly. It includes instructions on framing the shower stall, pouring the pre-slope and shower base mortar, and installing the shower pan membrane liner.

See HomeAdditionPlus.com’s Ceramic Tile Calculator

See my “How to Tile a Custom Ceramic Tile Shower” Ebook to learn how to tile your own shower:  For a detailed set of instructions on tiling a shower floor and walls, including pictures for every step in the process, see my “How to Tile Custom Ceramic Tile Shower Ebook”.

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