What is an Uncoupling Membrane? Why do You Need it?

Floor tiles and substrates tend to contract and expand at different rates due to changes in moisture levels and temperatures. Unfortunately, some people still install stone or ceramic tiles by bonding them directly to the substrate. As a result, these tiles split or crack over time. Alternatively, the tiles become de-bonded from the substrate due to the build-up of natural stresses.

To prevent these issues from happening, it’s important to prepare the subfloor before you install your tiles. Something you can easily accomplish by using an uncoupling mat or an underlayment. Doing so will prevent any subfloor movement that can cause grout or tiles to crack. But do you even know what an uncoupling membrane is or when to use it in your tile installation project?

What is Uncoupling Membrane? 

A dimple mat simply refers to a ⅛” thick plastic sheet. The surface is covered with square cavities while its back is made up of fleece or synthetic fabric.

The dimples anchor onto the top thin-set layer that adheres to the tile. On the contrary, the backing adheres to the thin-set mortar that’s laid to the subfloor. So a decoupling mat acts as a form of intermediate materials between the load-bearing substrates and the tile.

Also, their design allows them to neutralize lateral stress that may occur between the tile covering and the substrate. It’s also worth mentioning that uncoupling membranes are ideal for use over various substrates.

As an example, they’re ideal for use on concrete, timber, gypsum-based screeds as well as cementitious screeds. Better still, since the decoupling mat is made of plastic material like polyethylene, it’s completely water and moisture resistant.

Benefits of Uncoupling Membrane

Nowadays, most tile installers seem to be choosing decoupling membrane for tile underlayment over other methods like cement board/ backer board. Thanks to the several benefits they come with. Some of them include;

1. Moisture Resistant

As mentioned earlier, uncoupling membranes have outstanding waterproofing properties. So, if you seal the joints properly, they’ll effectively protect substrates from water infiltration. At the same time, this will help to extend the longevity of your uncoupling membrane system.

2. Prevents Tiles from Cracking & Lifting

Another benefit of using decoupling mats is that they prevent newly laid tiles from lifting or cracking. Especially when the subfloor cracks or moves in any way because of environmental or natural causes. For instance, the foundation of newly built structures settles into the ground, causing it to move slightly.

That slight movement is enough to cause tiles to crack or lift. However, that will not happen if you’ve got a decoupling membrane. Instead, the membrane will absorb the lateral movements, thus preventing the tile from breaking up or cracking.

3. Distributes Stresses on Floorings Effectively

Lastly, decoupling membranes allow the distribution of stress on tile floorings when subjected to heavy loads. Moreover, some mats ensure uniform heat distribution from underfloor heating systems to the floor tiles.

Why Use a Decoupling Membrane? 

For years, floor tiles installation has been done on reinforced mortar beds that move freely from the subfloor. Thanks to the use of a weakly bonded/ loose plane installed between the subfloor and the mortar bed. That way, if a crack forms due to the movement of the subfloor, it’s not transmitted to the tile surface through the underlayment.

Surprisingly, the installation method is still in use up to this day. But the un-bonded mortar technique can handle underpayments that are up to 1.5 – 2″ thick. Yet, most remodel and new construction buildings cannot handle such an extra weight or height.

Most modern projects involve the use of thin-set mortar during tile installation. And in an attempt to reduce the floor covering’s thickness, the thin-set mortar is bonded directly to the existing floor surface. In total, this increases the height of the floor by less than ½”. In addition, flexible mortars and bonded mortars have been developed to prevent cracks from moving to the floor tiles through the subfloor.

The use of crack isolation mats and mortars may not be suitable in some circumstances though. As an example, if you install tiles directly over a concrete slab too soon after pouring it, the tiles will crack or come loose.

That’s because concrete surfaces undergo constant changes as the concrete shrinks and cures during the 1st 30 days after pouring. In return, this develops stresses that are then transmitted to the installed floor tiles.

That’s where the installation of uncoupling membrane comes in! As mentioned earlier, the loosely bonded, bottom fleece of the membrane adheres to the subfloor. While tiles are attached to the membrane’s top surface, the membrane preserves the integrity of the tiles and absorbs any stress caused by substrate movement.


Provided you install an uncoupling properly, it will give many benefits to your tile floor. It has excellent waterproofing, load-bearing, and heat exchanging properties that will make your project a success.

You can install it on various subfloor surfaces such as plywood, concrete, gypsum, OSB, radiant heated floors, and even vinyl floors. And its lightweight nature allows faster installation, saving you a lot of time.


1. Are uncoupling membranes waterproof?

Uncoupling membranes have outstanding waterproof properties since they are made of polyethylene. For that, you can use them to waterproof substrates that are affected by moisture. This may include; wood, plasterboard as well as anhydrite.

2. How long do uncoupling membranes last?

Uncoupling mats can last for several years if they’re installed properly. This is because they’ve incredible resistance against water, weather elements, and chemicals.

3. Are uncoupling membranes expensive? 

Laying an uncoupling membrane plays a crucial role in extending the longevity of your tiled floor. However, they significantly increase the tile installation cost since they’re quite expensive.

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