Schluter-DITRA Tile Underlayment

By Todd Fratzel on Flooring

I tiled our bathroom and mudroom in the new house. One of the issues I needed to figure out was the transition between the 3/8″ thick engineered wood floor and the adjacent rooms with tile. Traditionally I would have installed 1/4″ cement board under the tile. Then the adjacent wood floor would have needed a thin layer of wood underlayment to match up with the tile floor thickness. After talking to my cousin (he sells and installs flooring) he suggested that I try using the Schluter-DITRA underlayment under the tile floors.

Schluter-DITRA is polyethylene membrane with a grid structure of square cavities, each cut back in a dovetail configuration, and an anchoring fleece laminated to its underside. The biggest advantage to this product is it’s ability to act as an “uncoupling” layer. The membrane allows for in plane movement due to horizontal shear forces. You ask what the heck does that mean? Well in simple terms every time the floor changes temperature, moisture content or a load is applied (people) the floor flexes and causes a shearing force between the tile and sub-floor. This membrane allows for that movement without causing the tile to break.

The installation is actually quite simple. You role out the product (it comes in a role 3′-3″ wide) and cut it to fit the room. After you’ve cut all the pieces you adhere it to the sub-floor using thin set mortar. The fleece on the bottom of the membrane adheres to the sub-floor with the thin set. You use a regular rubber grout trowel to smooth out the membrane and make sure it is fully seated in the thin set.

The next step is to lay the tile as you normally would over a cement board application. The manufacturer even says you can apply the tile right away before the first layer of thin set has cured. I actually found laying the tile on this product much easier than the traditional cement board. The membrane is much softer to kneel on and the squares act as a great grid to help you maintain straight grout lines.

Tools I recommend:

I successfully used this product a year and a half ago and the tile floors are performing great. I even have radiant heat and that works great with this product. Next time I tile a floor I’m definitely going to use it. If you’re looking for cheap prices on Schluter Ditra then click the banner below. - Ditra as low as 99 cents per square foot!

About the author

Todd Fratzel

I'm full time builder for a large construction company in New Hampshire. I run their design-build division that specializes in custom homes, commercial design-build projects and sub-divisions. I'm also a licensed civil and structural engineer with extensive experience in civil and structural design and home construction. My hope is that I can share my experience in the home construction, home improvement and home renovation profession with other builders and home owners. I'm also the Editor-in-Chief and Founder of Tool Box Buzz. Please feel free to contact me if you have any questions, suggestions or you'd like to inquire about advertising on this site.

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  1. Scott Rossow says:

    Have you ever heard of Viega Climate Panels? I have the panels installed over a concrete floor that is 16′ x 16′. I am hesitant on adding 1/2″ CBU to the top of the panel since I don’t want to add height to the floor as well as possible damage to the PEX tube running in the Viega boards. Schluter says they won’t guarantee Ditra mounted over the panels in thinset. I don’t entirely understand why since the Ditra is an “uncoupling” layer, which I would assume would work great in an application such as Viega. Any ideas are greatly appreciated.

    • Todd says:

      Scott – I haven’t personally used that system in the past. I’m not entirely sure why Schulter would say that other than they are probably covering their “A SS”. It also may have something to do with how the Viega panels are attached to the concrete. would it be possible to test a small section…see how it sits on those panels with the thinset?

      • Joe says:

        Hmm, I am having the same question and getting various answers from tile contractors. I have a 40′ by 14′ addition room with wood subfloor that will have the Viega climate panels with radiant pex tubing. Trying to figure out the best underlayment for on top of that. 1/4 cement board or the ditra solution. Argggh, just want to know what the best solution is!!

        • Todd says:

          Joe – Sounds to me that maybe you should try another radiant solution…just a thought. We always use radiant tubes that are attached below the floor. Sorry I can’t be much help on this issue.

  2. Bostonguy says:

    I have a concrete floor in my basement which was painted by the previous owner (I just moved in 2 months ago) and the paint is peeling right off due to moisture. I fixed a downspout issue which was letting water in but there are still some spotty areas on the floor that get damp/wet. What can I do to fix this issue? It is an unfinished basement w/ concrete floors and block foundation walls. I was told to lay mortar and tile over the existing floor and upon looking for solutions came across this article. Would adding this membrane with thin set, then adding tile on top “fix” my problem? or just hide it underneath. The reason i ask is that I was told the mortar laid on top of the basement floor would keep the moisture from protruding. Adding the rest on top (membrane with more mortar and tiles) would just be overkill? I would gratefully appreciate any advise or suggestions as a new homeowner.

    • Todd says:

      Mortar isn’t going to fix a moisture problem. It’s likely that the builder didn’t use a vapor barrier under the slap. DITRA will certainly act as a vapor barrier but you need to get the loose paint off first.

      • Bostonguy says:

        My house was built in 1940 and so I’m not sure if they had/knew what vapor barriers did. I had a cracked corner underneath the set of stairs going into the basement that I decided to to open and clean (to repair) and found out that theres is about a 2″ slab of concrete thickness on my basement floors. They are not level but as mentioned, has loose paint which I will scrape off. Once I do that, how do I go about preparing the floor for tile? scrape paint, clean and then lay some DITRA on the mortar with more on top and finally the tiles?

        • Todd says:

          Couple of thoughts before the how’s on tiling.

          With only a 2″ slab it’s likely that you will get cracking in your new floor at some point due to movement in the slab. Of course there’s a possibility that won’t happen if you have a really great sub-base but frankly it’s quite risky. So…if you want to tile it beware that you may have problems.

          Schluter-DITRA is really easy to work with. First you put down a layer of thinset (follow manufactures spec sheet closely for the type) and lay the DITRA in that. This creates a bond between the concrete and the DITRA. Then you simply use thinset and tile over the DITRA like any normal tiling situation. I really like using this stuff for several reasons.

          This product will certainly help stop cracking as it allows the slab to do it thing while protecting the tile. Just not sure if it will prevent 100% of problems with a slab that thin.

  3. Bostonguy says:

    Todd, thanks for your great advice. I could be wrong about the size of the concrete but nevertheless great tips and help. Thanks again!

  4. Mark says:

    I installed an insulated subfloor over my concrete basement. Planning on using ditra with tiles. The floor has some unlevel spots though, but they are gradual for the most part. High spots mostly towards the wall. Can I just build up the base with thinset when putting down the ditra and tiles to even it out? Or do I need to get into some sort of self leveling product?

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