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Schluter DITRA Over Wood in a Bathroom

Cracked floor tiles are bad.

There’s a simple solution: Schluter DITRA

DITRA can be installed on wood or concrete subfloors.

Then, tile can be set on top of the DITRA.

Today, I’ll show you how to install DITRA on a wood subfloor.

Why Use Schluter DITRA 

Tile floors look beautiful.

But broken tiles don’t look great.

Broken Tile

Cracked tiles are an issue when the substrate isn’t prepared properly.

I check three things before setting a tile

  1. The joist span, e.g. 16″ on-center
  2. The subfloor thickness, e.g. 5/8″ or 3/4″ are good
  3. The DITRA Handbook

The DITRA Handbook has specific tips for subfloor thickness based on the joist span and tile species.

It’s an excellent source of information and should always be read prior to setting tiles.

The best part is anyone can read the DITRA Handbook and for the most part understand it.

The Benefits of DITRA

DITRA is way easier to install than cement board.

First, it’s light.

Second, it stops tile and grout from cracking.

Third, it can waterproof the wood subfloor.

How to Waterproof DITRA

DITRA can prevent mold and mildew from forming on wood subfloors.

I will show you how to install DITRA today and make it 100% waterproof.

Here are the supplies you need

So what’s the first step when installing DITRA on a wood subfloor?

Know the Framing of Your Home

Schluter DITRA has the best technical support.

I constantly call my Schlute rep or the 800 tech support number.

They answer the phone every time!

Schluter also has the best installation directions.

Hey, they’re German and you know what that means…DETAILS my friend.


I always find the joist spacing before installing DITRA.

Here’s the basic rundown of how to use DITRA for ceramic or porcelain tile

  1. 16 inch on-center joist spacing with single-layer OSB or plywood subfloors
  2. 19.2 inch on-center joist spacing with single-layer OSB or plywood subfloors
  3. 24 inch on-center joist spacing with double-layer OSB or plywood subfloors
  4. 24 inch on-center joist spacing with single-layer OSB or plywood subfloors

Please read the DITRA Handbook to double-check these requirements. The Handbook can always change.

Each configuration has specific guidance for

  • subfloor requirements
  • substrate preparation
  • movement joints
  • thin-set, grout, and more.

DITRA can be installed over the following surfaces

  • plywood
  • existing vinyl floors
  • structural plank subfloors
  • concrete
  • and heated floors.

This tutorial is just for wood subfloors.

All the specifics for DITRA installation are in the handbook or on Schluter’s site.


I ensure subfloor panels are flat and properly fastened to the joists.

In addition, I Inspect the floor for protruding nails or screws and fix squeaks before moving forward.

Subfloors should have a 1/8″ gap between wood panels.

Tight subfloor seams don’t allow space for expansion and contraction.

If the subfloor lacks an expansion joint, it can tent. That tenting can cause tiles to crack.

Install Schluter DITRA Over Wood Subfloors

DITRA can be installed over plywood or OSB.

Schluter recommends using a modified thin-set over wood subfloors. Schluter ALL-SET is a modified thin-set and great option for setting DITRA

Schluter ALL-SET

I mix ALL-SET according to the membrane water ratio.

The ALL-SET should hold a notch but still be fairly fluid.

If I don’t use Schluter ALL-SET, I look on the bag for ANSI A118.1 and that’s an indicator that the thin-set is modified.

I measure the floor dimensions and cut my DITRA with a utility knife.

Then I dry fit the DITRA

And I clean and dampen the wood subfloor. This step is very important because it prevents the wood from sucking the moisture from the thin-set mortar.

This creates a solid bond between the thin-set and DITRA.

I use the KERDI trowel to apply thin-set to the subfloor for DITRA.

Here are the trowel sizes that can be used to set DITRA in thin-set

  • 1/4″ x 3/16″ V-notched or
  • 5/16″ x 5/16″ V-notched trowel or
  • DITRA trowel which features a 11/64″ x 11/64″ square-notched design

I apply the thin-set to the wood subfloor and make the trowel notches all run in the same direction.

How to apply thin-set for DITRA

Then I embed the fleece side of the DITRA in the thin-set, leave a 1/4″ gap between walls and membrane, and use a float to push the DITRA into the thin-set

How to install DITRA membrane

I lift up a corner of the DITRA to check for thin-set coverage.

The goal should be 100% coverage.

Here’s a short video that shares some tips

How to Make DITRA Waterproof 

I fill the cavities with unmodified thin-set mortar or Schluter ALL-SET

Then I comb additional thin-set over the joint using an approved trowel, e.g. the KERDI trowel.

Finally, I center the 5-inch wide KERDI-BAND over the joint and use the flat side of a joint compound knife to press the banding into the mortar.

How to waterproof DITRA

I use this method where DITRA meets drywall and other sheets of DITRA.

The gap between the bathtub and floor is notorious for water leaks.

I fill the 1/4 inch gap between the DITRA and tub with KERDI-FIX.

Then I fill in the cavities with ALL-SET and embed the 5-inch wide KERDI-BAND

Here’s a nice tutorial with several important tips for how to install DITRA

What’s Next

If you’re remodeling a bathroom and need help, join our Platinum Membership and make your project easier with over 250 step-by-step tutorials.

We show how to build showers install tile, upgrade basement bathrooms, and more.

The extra guidance is invaluable.

Thanks for reading and watching our tutorials and we hope to see you inside Home Repair Tutor!



DITRA Over Wood

  1. Faye says:

    Hi, I have a wooden sub-floor in my 1/2 bath that appears to be level to the naked eye. Do I need to use a leveling product before using DITRA, or will DITRA take care of any minor inconsistencies? Also, I think I need to pull out vanity, baseboards and toilet, install DITRA and then tile entire bath before reinstalling new toilet, vanity and baseboards. Is this correct? I may just surprise my husband by remodeling our 1/2 bath by myself! Thx!

    1. You’re right Faye, you need to remove the toilet, vanity and baseboards to install DITRA over your subfloor. And it should be as level as possible. DITRA is only 1/8″ thick so it won’t help with hills or valleys in your subfloor. You’ll have to sand those down or level them 😉

      Let me know if you have any questions along your journey, I’d be happy to help

  2. Dave C. says:

    Unlike Faye above, I know my subfloor is not level. When I pulled up the contractor grade sheet flooring, the leveling material came away in patches. So I removed it all to the plywood. The peel n stick tile I put down cracked within a year. Can I use a self leveling product under DITRA? I don’t think I can redo the subfloor.

    1. You can use self-leveling material under DITRA Dave, just make sure it’s completely dry before applying the thin-set.

      Sorry to hear about your issues, awe homeownership, the joys of DIY!!

  3. Elmer says:

    How about over vinyl tiles?.

    1. You can install DITRA over vinyl but make sure to follow the Schluter directions to a “T”.

      I’d personally recommend tearing up the tiles so as to inspect the subfloor for any damage.

      But if you’re sure the subfloor is solid, no water damage, and there aren’t other products under the vinyl…you could install DITRA over it.

  4. Ron says:

    Hi Jeff. Here, on the podcast, and in the videos it says to lay down MODIFIED thin-set. It also says to use ANSI A118.1. However, ANSI A118.1 is for unmodified thin-set (ANSI A118.4 is for modified). Also, the Schluter installation handbook also recommends using unmodified thin-set (ANSI A118.1) to lay down Ditra over wood. Am I misreading this?

    1. Ron says:

      Hi Jeff. I re-read Schluter’s install guide and you are correct to set the Ditra down it should use MODIFIED thin-set However, the standard above for MODIFIED should ANSI A118.11 (its currently listed as ANSI A118.1 which is for unmodified thin-set).

  5. Ken says:

    I am planning to put porcelai tiles on top of ditra. The Ditra will be on the vinyl over plywood. The installation manual says that I need to put a screw/nail through vinyl/ply every 4 inches that is about 9 nails per square foot. This is too much of screws. Is it really needed?

  6. Gilles Morin says:

    Is it better to put cement boards on wood floor first before installing Ditra?

  7. Joyce Brown says:

    I am really interested in your product but I have a question, how would you install this product if part of your design includes a radiant floor. Can/should the radiant floor be installed on top? If so is there a restriction of which type of floor install?
    Thank you

    1. Patrick Coberley says:

      Joyce, great news. Schluter makes a radiant floor system called Ditra Heat. It is an all inclusive system; mat, wiring, etc.
      Easiest install on the market.

  8. Ken Stevens says:

    What are the benefits of Ditra over the RedGard uncoupling mat? I see the Ditra installation uses both modified and modified thinset. Wouldn’t the RedGard be less complicated due to using all modified thinset?

    1. One way to cut down on the confusion Ken is to use Schluter’s ALL-SET. It’s a thin-set meant for both under and over DITRA. We like DITRA because it’s never failed us and the installation is very straight forward.

  9. Jane DIY ADDICT says:

    We use Schluter kerdi shower kit 72 x72 had purchase extra corners and also ditra heat , purchased extra band to join sheets. We also bought schluter thinset which is very expensive but we wanted the full warranty. It been a great deal of work and not as easy as it looks. Now planning out tile placement in all the shower area including ceiling and bathroom floor and walls…so much planning and time envolved

  10. Jane DIY ADDICT says:

    Can you make a video on tiling the shower ceiling with smaller mosaic tile and to keep in place and how yo cut these tiles on a wet saw without them falling off the webbed backing. This was one challenging job please help anyone else trying to do this, using schluter thinset. THANKS GUYS !

  11. Jane DIY ADDICT says:

    To Gilles Morin , no need to install cement over wood floor, please look on website. It will explain what is needed, even thickness of flooring needed. You can even send them a message or call they will reply

  12. Steve says:

    Can I use ditra over cement board like duroc?

  13. Tomas says:

    My toilet leaked and created some water damage into the lower floor. I plan on replacing the plywood subfloor in the entire bathroom before adding the Ditra floor.
    What kind and thickness of plywood do you recommend to use with the Shluter?

  14. Ning says:

    Do I have to tile over the Kerdi band where floor.meets wll or can I install pvc moulding?

  15. Brooke says:

    When I removed a cracked tile in my kitchen to replace it, the corner of the Ditra pulled up. Is there a way to reattach it or is it okay to go ahead and replace the tile?

  16. Vinod says:


    If the plywood floor in the bathroom is not level, do you recommend using a self leveling compound and then installing Ditra over it?

  17. Matt says:

    I’m considering installing a wood-like ceramic tile over existing wood flooring which consists of 2x wood plank subfloor (not plywood sheathing) with finish wood flooring on top. What is your recommendation to install Ditra over existing flooring? My initial thoughts include removing the existing finish wood floor, then install Ditra and modified thin set over the wood plank floor, and lastly unmodified and ceramic tile over Ditra. I’m interesting in hearing your thoughts before I begin my renovation.

  18. Patrick says:

    Hi, I just removed all of the old ceramic tile in my bathroom. Vanity and toilet have been removed, and the new tub has been installed. When removing the old tile, I realized the floor is not perfectly level, due to the old mortar. Can you recommend a self leveling product to use, before placing down the ditra? Also, would you be able to confirm that Mapei uncoupling membrane mortar (thin -set) is the correct product to use over the self leveling product that should be placed on the plywood subfloor? Additionally, can I use the same thin set on top of the ditra to fill in the waffles and cover the seems between the ditra?

    Thanks for all your help!!

  19. Roxanne McCallister says:

    We are looking at using Ditra to retile our kitchen. We have 16″ floor joist with a 3/8″ plywood, a layer of tar paper, then 3/4″ tongue and groove Drymax. I read over the Schluter PDF where it had the strengths of various types of tile listed as well as a lot of other data regarding the product. We were wondering what the maximum size of tile we can install is? We have been told that you can’t use tiles much larger than 16×16 with a wood floor and crawlspace. We weren’t sure this applied to the Ditra products or not. We found a 12×48 ceramic tile we fell in love with and I would like to know if that would be fine or would there be issues with it cracking?

  20. Christopher says:

    I just laid my ditra on my bathroom floor. I had to patch a piece of rotted subfloor and one corner of the is sitting Higher on the patch then the surrounding subfloor. Help!

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