Do you have a floor tile project in the future?  If so, I highly recommend installing Schluter DITRA first!  In this post, I will explain what DITRA is and why you should use it, provide a list of required tools, and explain how to complete DITRA installation in 5 easy steps!

This post is all about the Schluter DITRA installation

The project I will share in this post is one of two bathrooms we created from a Jack and Jill Bathroom.  I am preparing to lay floor tile in the smaller of the two bathrooms.  I will be installing Schluter DITRA over plywood. The existing plywood subfloor upon which I will install the tiling uncoupling membrane is a single layer of plywood.

DITRA can be used on a wide range of substrates, including wood or concrete; however, this post will only explain how to install it over a single layer of wood subfloor.  For DITRA installation instructions on other types of subfloors and more detailed information, please reference the DITRA Installation Handbook.

What is Schluter DITRA?

DITRA is an uncoupling and waterproofing membrane specifically designed for the installation of stone and ceramic tiles.  It is a 1/8″ thick uncoupling membrane intended to replace cement backer board.  It has a polyethylene membrane top layer with a honeycomb-like design (square cavities)and an anchoring fleece layer on the underside that is embedded in mortar.

Why You Should Use DITRA

Once installed, DITRA serves four critical functions:

1.  Uncoupling

The DITRA underlayment helps prevent tile cracking and delaminating due to stresses between the tile and the subfloor by allowing for in-plane movement.

2.  Waterproofing

DITRA’s polyethylene composition helps to prevent moisture from making its way to the subfloor.

3.  Vapor Management

Schluter membrane installation helps to prevent moisture and vapor from the subfloor from reaching the tile where it otherwise might cause damage.

4.  Support/Load Distribution

The honeycomb-like design of DITRA helps to transfer load from the tile through the columns created by the cells to the subfloor.  DITRA can evenly distribute heavy loads without affecting the tile’s integrity.

Tools Required

​As a reminder, I am sharing information about installing DITRA over plywood.  If you have a different substrate, make sure to look up the installation instructions (and required tools) for your particular substrate.  The DITRA Installation Handbook is a great resource!

• DITRA Membrane
• DITRA-TROWEL, a 1/4″ x 3/16″ V-notched trowel, or a 5/16″ x 5/16″ V-notched trowel
• All-Set, Fast-Set, or Modified Thinset Mortar – ANSI A118.11
• Bucket
• Thin-Set Mixing Paddle
• Corded Drill
• Clean Water
• Float, DITRA-ROLLER, or a Piece of 2″ x 4″
• Shop Vac
• Microfiber Rags or Mop
• Scissors
• Measuring Tape
• Utility Knife

DITRA Installation

1.  Prepare the Subfloor

The subfloor must be level for a proper installation.  If you have to take any steps to level the floor, you must do it before installing the DITRA membrane.  This is also the time to ensure your plywood, or OSB, is adequately secured and that the seams are tight.

Before installing the Schluter DITRA uncoupling membrane, it is essential to ensure the subfloor is also clean.  I use a shop vac to vacuum debris and dust, then a damp microfiber mop or cloth to remove any remaining dust.

 

2.  Cut the DITRA

It is now time to measure the space where you will install the DITRA uncoupling membrane and cut it to fit.  When measuring for the DITRA, you want to leave 1/2″ of space around the perimeter.  Make sure any seams between pieces of DITRA are tight but not overlapping.

I use scissors to cut the tile underlayment and a utility knife to cut around penetrations in the floor.  Once you have cut the DITRA to fit the space, I recommend laying it out flat to let it flatten out.

If you are installing the DITRA in a large space, it might help to place a mark at the base of the wall where your seams are so you know where to place your pieces.

 

3.  Mix the Mortar

Now that you have cut the DITRA, the next step is to mix the mortar.  Check the manufacturer’s mixing instructions for your mortar of choice.  Typically, you will mix for some time, let it rest, then mix again.

Each mortar is different, so just follow the instructions on the bag.  Schluter recommends a fluid consistency but stiff enough to hold a notch.

Helpful Hint:  Pay attention to the working time and only mix up as much as you think you can use in that amount of time.  Feeling pressed for time can make this process more stressful than it has to be.

 

4.  Spread the Mortar

Using your preferred trowel from the Tools Required list above (I use a 1/4″ x 3/16″ V-notched trowel), spread the mortar out using the flat side of the trowel first.  You do this to ensure a good bond with the substrate.

Once you have spread it out over the subfloor, it is time to trowel using the notched side.  It is best to trowel in one direction while holding it at a 45-degree angle.

Helpful Hint:  Do not apply so much mortar that you cannot reach the farthest point to lay the DITRA in place.  In this bathroom, I spread about three feet, then set the DITRA in place with the unused portion still rolled up.

 

5.  Lay the DITRA in Place

Once you have troweled the mortar, it is time to lay the DITRA in place carefully.  It is essential to ensure the DITRA is embedded in the mortar.  I use a piece of 2″ x 4″ (DITRA recommends a float or a roller) to go over the DITRA, applying pressure to ensure it is properly embedded.

You can use the float or your fingers to apply pressure along the walls to press the DITRA into the mortar.  I recommend gently pulling up a corner to verify the fleece is achieving complete contact with the mortar.

 

​Optional Step

When you reach this point, you are essentially finished with the installation of the DITRA membrane and can start the floor tile installation!  Part of the tile-laying process includes filling the honeycomb-like spaces in the DITRA with the mortar you will use to lay the tile.

Schluter recommends using their ALL SET, FAST SET, or an unmodified thin-set mortar.  You can fill the spaces now or wait until you lay the tile.

I fill the spaces when I lay the tile.  The fewer batches of mortar I have to mix, the happier I am!

Summary

In this post, I explained what DITRA is and why you should use it, provided a list of the required tools, and explained how to install Schluter membrane in just 5 simple steps!  You should now have all the information you need to successfully install DITRA for an even better floor tile job!

If you are planning a bathroom renovation, you might be interested in my posts, DIY Cost to Remodel a Small Bathroom, Best Grout for Shower Tile: How to Choose the Perfect One, and Penny Tile Shower Floor Pros and Cons.