Install DITRA on a Wood Subfloor (stop Cracked Tiles)

Introduction: Install DITRA on a Wood Subfloor (stop Cracked Tiles)

About: We love home improvement and enjoy sharing tips on YouTube and Home Repair Tutor. Everything we do is self taught. Over the last 12 years we've bought and rehabbed several rental homes in Pittsburgh. Somet...

Cracked floor tiles stink…REALLY BAD

There’s a simple solution: DITRA

It goes down on top of wood or concrete subfloors.

Your tile then goes on the DITRA.

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

PLUS you get to see a pro tile installer do it.

This tutorials is gonna make your tile installation way faster!!

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Step 1: Gather Materials

Tile floors…there’s no doubt they make homes look nicer.

But what’s not so awesome are broken tiles.

This is a HUGE issue if your home settles over time.

Guess what, all homes settle!!!!!!!

DITRA solves this problem?

The best part is anyone can install it.

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.

If you’re afraid of mold in the bathroom DITRA will help. Steve and I will show you how to install DITRA today and make it 100% waterproof. Here are the supplies you need

  • Schluter DITRA
  • Schluter DITRA Trowel
  • Schluter KERDI-BAND
  • Schluter KERDI Trowel
  • Utility Knife
  • Modified Thin-set (Ardex and Mapei make great thin-set)
  • Unmodified Thin-set
  • Caulking Gun
  • 1/2″ Drill (for mixing thin-set)
  • QEP Super Grout Mixer (for mixing thin-set)
  • Rubber Grout Float
  • Five Gallon Bucket
  • Nitrile Gloves

Step 2: Know Joist Spacing

Know the joist spacing of your home before installing DITRA.

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

  • 16 inch on-center joist spacing with single layer OSB or plywood subfloor
  • 19.2 inch on-center joist spacing with single layer OSB or plywood subfloors
  • 24 inch on-center joist spacing with double layer OSB or plywood subfloors
  • 24 inch on-center joist spacing with single layer OSB or plywood subfloors

Each configuration has specific guidance for:

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

Basically you can install DITRA over

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

BUT again, this tutorial is just for wood subfloors.

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

IN GENERAL: ensure subfloor panels are level and properly fastened to the joists.

Inspect the floor for protruding nails or screws (fix squeaks before installing any flooring).

Step 3: Mix Modified Thin-Set

Once your subfloor is good to go it’s time to install the DITRA.

Mix up modified thin-set.

Thin-set should be mixed to a fairly fluid consistency.

BUT should still hold a notch.

How do you know you have the right modified thin-set?

Look on the bag for ANSI A118.1.

Again, modified thin-set is what you want between DITRA and the wood subfloor.

Step 4: Measure Floor Dimensions and Cut DITRA

Measure the floor dimensions and cut your DITRA.

You can cut DITRA with a utility knife.

Step 5: Dry Fit DITRA

Dry fit the DITRA on your wood subfloor.

Step 6: Clean & Dampen Wood Subfloor

Clean and dampen the wood subfloor.

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

Step 7: Apply Modified Thin-Set

What trowel should you use to apply thin-set to the wood subfloor?

Check it out, we’ve got you covered

  • 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

How’s that for detail!!

Apply the modified thin-set to the wood subfloor.

Notches should all run in the same direction.

Step 8: Embed DITRA Into Thin-Set

Embed the fleece side of the DITRA in the thin-set.

Leave a 1/4″ gap between walls and the bathtub.

Use a rubber grout float to push the DITRA into the thin-set

Step 9: Check Thin-Set Coverage

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

Your goal should be 100% coverage…we had a few bare spots here and fixed that issue!!

Step 10: Abut End and Side Sections

You can abut end and side sections of adjacent DITRA sheets.

Step 11: Watch the Video Tutorial (Part 1)

Watch our step-by-step video for all the juicy details

The beginning shows you why I like DITRA versus cement board

This is Part 1 and shares the entire step-by-step of installing DITRA on a wood subfloor.

Step 12: Start the Waterproofing...

So how easy is it to waterproof DITRA?

Pretty darn simple.

At the joints, fill the cavities with unmodified thin-set mortar.

Make about an 8 inch band of thin-set centered over DITRA joints.

Step 13: Center KERDI-BAND Over Joints

Comb additional thin-set over the joint using an approved trowel.

Center the 5 inch wide KERDI-BAND over the joint.

Step 14: Firmly Press KERDI-BAND Into Thin-Set

With the flat side of the trowel, firmly press the KERDI-BAND into the mortar.

Make sure to fully embed the KERDI-BAND and remove any excess mortar and air pockets.

You can use this same method where DITRA meets drywall.

We used a 5 inch wide KERDI-BAND because if it’s centered, your base molding will hide it.

Check out the video for those details.

Step 15: Fill Gap Between Tub and DITRA

One of the worst spots for water damage is where your tub meets the tile floor.

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

Step 16: Embed KERDI-BAND

Fill in the cavities with unmodified thin-set and embed the 5 inch wide KERDI-BAND

Step 17: Watch the Part 2 Video on DITRA Waterproofing

Steve shows you the exact method in our video,

you’ll be a whiz at DITRA installation after today!

DITRA is the easiest way to waterproof your floor and prevent tile & grout from cracking.

What do you think, do you feel like you could install DITRA?

Let me know in the comments.

ALSO: if you have a question, fire away in the comments.

As you can tell…I’d love to hear from you, haha.

Thanks for reading, watching and being an awesome DIYer.


Founder, Home Repair Tutor

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    14 Discussions


    7 months ago

    I wish to use Ditra over my plywood floors. What thickness must my plywood floors be to do this?


    Question 1 year ago on Introduction

    Ok, I have a wood kitchen floor that consists of the following

    Concert footing

    Joists are 16”

    2x8 boards set diagonally

    3/8” plywood on top

    We installed the distra two days ago. It appears solid. Now we have an installer that says we needed no less the 3/4” plywood and he won’t guarantee the work.


    Question 1 year ago

    Thanks for the post!! Well done! Ok let me get this straight, to install Ditra heat over a plywood floor, I need MODIFIED thinset. When waterproofing the joints between ditra membranes or cavities with the wall, I need an UNMODIFIED thinset?

    But I need MODIFIED thinset when tiling over the ditra heat membrane, correct?


    2 years ago

    "How do you know you have the right modified thin-set?

    Look on the bag for ANSI A118.1."

    By following your instructable, I ended up using un-modified thinset on my wood subfloor and then modified thinset over the Ditra.

    Please fix the wording here. ANSI A118.1 means that it is UN-modified! ?


    3 years ago

    I can sure see some advantages of this for a project. You could haul 1000 square feet in the back of my Expedition without the need to barrow a trailer. However, I see this stuff is pricey at nearly twice what hardybacker runs not counting the thinset. So, just so happens I am in the middle of repairing the floor (a small amount of termite damage) in a large living room. (28' by 16') then on to the dining room then kitchen as part of an over all remodel. I don't need to water proof the larger rooms. Would you still need to use the kardi bands? With the waffle squares, I see it using quite a bit more thinset, so how much more should you figure on using?


    Reply 3 years ago

    I forgot to ask about suggestions for radiant heat underlayments. Do you have any suggestions for that?


    Reply 3 years ago

    You could actually opt for DITRA-HEAT, that solves two problems with one substrate. Worth checking out


    Reply 3 years ago

    The benefit of using DITRA over cement board is like you said the ease of installation but also the fact that it protects the tiles from cracking...for me those two reasons are big. If you're not waterproofing the room you don't need the KERDI-BAND at the transitions, so one less expense. You do need to fill in the waffles with unmodified thin-set. Schluter recommends one 50lb bag of thin-set per 40-50 sq feet of tiled floor if you're using a 1/4" x 3/8" square-notched trowel. Always buy more than you need and return what's unused. That way you're not running back to the store.


    3 years ago

    I just love Ditra! Used in on two bathroom floors, first time I had ever done floor tile. Years later, no cracks. PLUS, didn't have to lug cement board to the second flor


    Reply 3 years ago

    Amen, lugging cement board up steps and more of that.


    3 years ago

    looks like great stuff. There seems to be an inordinate amount of Kerri resources required. Are there any readily available substitutes for the Kerdi materials?


    Reply 3 years ago

    KERDI is Schluter's foam board for tiling showers and there are other foam board products out there. In terms of DITRA, I think Lowe's made a similar product and Noble makes a thin membrane that also can be applied over plywood.


    3 years ago

    This is a great advertisement. I really don't see how this is any better that tile board. At least tile board has been tested with time.


    Reply 3 years ago

    Don't agree at all gunguru...DITRA has been around for a long time and used by the best tile setters. It's lighter, easier to cut and prevents tile from cracking...unlike cement board. Plus it doesn't add to the height of the finished floor like Hardiebacker or cement board. Schluter has done extensive research with DITRA and all their products and provides fantastic customer support. I've called them many times and have gotten answers every time.