Tile Underlayment Membrane

Schluter-Ditra Tile Underlayment is a polyethylene membrane that replaces 1/2″ cement backer board when applying tile over a plywood subfloor. At only 1/8″ thick, it can significantly reduce the finished height of a tile floor.

The flexible membrane comes in rolls and weighs only two ounces per square foot. After being cut to length, it’s set in a bed of thin-set mortar then covered by another coat of thin-set in which the tiles are laid. The membrane acts as an uncoupling layer to prevent cracking as well as providing waterproofing in one easy application.

Ditra Tile Underlayment is available at The Home Depot stores.

Further Information


  1. Hi:

    I want to replace some linoleum with tile in my kitchen and bathroom. The sub floor is cement (Condo built in the 80’s). Will this stuff work on a cement sub floor?

  2. i live in the netherlands and am preparing to tile my new kitchen’s countertops. we’ve been researching different ways to create a good underlayment, and most of the US sites either refer to cement/fiberglass backerboard or polyethylene membrane. we’ve also talked to hardware & kitchen installers here and they have frequently told us that we should simply use 3/4inch plywood, and carefully waterproof-varnish it on both sides. since NONE of the DIY sites i’ve seen have mentioned this as a possible method, i wonder what your opinion is of it? it seems a lot simpler, esp since i haven’t yet seen cement backerboard in the stores, but it also seems unlikely to work properly. can you advise me? thanks!

    • Hi Sharon,
      Varnishing the plywood subfloor under tile is a new one to me, but if you can’t get cement backer board over there, it would probably be better than nothing. Since cement backer board would be difficult to ship, you might try ordering the membrane online and having it shipped to you.
      Good luck with your project!

  3. I too had this problem, as putting down cement board would have made the height of the floor too high and I used marine spar varnish on the existing plywood to seal it. 9 years later, it seems to be still working.

  4. I’m tiling my bathroom and installing electric radiant heat. I also want to install a membrane under the tile to help with moisture and flex. Do I put the membrane under the wiring or over it?



    • Hi Beverly,
      To purchase tile underlayment membrane, check your local Home Depot store or click on the Schluter-Ditra link in the article above and use their dealer locator option in the navigation on the left. Good luck with your project!

    • Hi Don,
      The tile underlayment membrane eliminates the need for cement backer board, so you can use it on top of a plywood subfloor. The thickness of the plywood subfloor needed under the membrane will depend on the spacing of the joists and other factors. You can find out more in our article on Installing Tile Over a Wood Subfloor. Good luck with your project!

  5. I was told to use sureply as an underlayment. Now I am told I should have used ditra or cement board. Is there any proper way, such as some kind of coating I could put on the sureply, to put porcelain tile over this. I have a subfloor of 3/4 plywood with another 1/2 plywood.

  6. I want to lay tiles over a concrete ground floor area comprising one half which was part of the original build, and another half which is part of a recent extension. Significantly, the extension is built on piles whilst the original house was not. The ground beneath is mainly clay. Will this underlay prevent cracks or should we avoid tiles altogether?

  7. 18 years Ago I tiled my kitchen over3/4 plywood using 90 % thinset & 10% Elmer’s construction glue. To date I have had no problems with cracking of grout or tile! Just saying.

    Ed Donnelly

  8. I want to apply 12 x 24 ” porcelain tiles over 3/4 osb. 12″ high manufactured (scissor style) floor joists; 18-20″ o.c nailed every six inches. Should another underlayment be used and what is best and what thickness?


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