How to Install DITRA-HEAT Flooring Systems

This guide will help you understand the key steps for installing DITRA-HEAT floor heating systems. Always refer to the manufacturer’s handbook for specific instructions.

Watch the video below and read through our installation guide. If you have questions about the installation process or the products needed, please reach out to the Warm Your Floor team. We are always happy to help!

Tools & Materials Needed for DITRA-HEAT Installation

Standard Installation Tools

• Trowels – for spreading thinset mortar
• Utility knife – for cutting DITRA-HEAT membrane
• Thin-set mortar – for adhering membrane to subfloor
• Rubber float – for pressing membrane into mortar
• Multimeter – for testing conductor resistance

DITRA-HEAT specific materials

• Membrane
• Cable
• Thermostat

Build a Floor Heating Kit

Planning the Layout

Calculating Heated Area

Before installing your DITRA-HEAT system, you need to calculate your heated area to determine the amount of DITRA-HEAT membrane and cable required.

If you need additional help, contact one of Warm Your Floor’s experts for quick assistance. Be sure to include the drawing and your contact information.

Determining Cable Layout

After you figure out your heated area, you need to determine your heating cable layout. This is a very important step that requires several considerations:   

• Do not purchase a heating cable that is the same size as the area to be tiled; you will be left with too much heating cable!
• Very important: Never CUT or modify the heating cable in any way. This would change the cable resistance, will cause damage to the cable, and could cause cable overheating.
• A cable spacing of 3 studs is standard.
• Cable may also be spaced at continuously alternating 3 stud – 2 stud intervals in isolated areas or over the entire floor. This practice may be desirable to increase heat output (e.g., over uninsulated on or below grade concrete subfloors) or to consume more cable length in a given area (e.g., when using the standard 3 stud spacing doesn’t allow the selected cable to fit the floor area and respect minimum spacing requirements from walls, partitions, etc.)
• A cable spacing of 4 studs is not recommended, as it can produce inconsistent floor surface temperatures.
• Minimum spacing from walls, partitions, and fixed cabinets is 2″ (50 mm).
• Minimum spacing from other heat sources (baseboard heaters, other fixed heating devices, fireplaces, etc.) is 8″ (200 mm).
• Minimum spacing from any plumbing drain and forced air heating duct  is 4″ (100 mm).
• Minimum spacing from centerline of toilet drains is 7″ (180 mm).
• NEVER install the heating cable under vanities with no air space beneath, bathtub platforms, free standing bathtubs with no air space beneath, kitchen cabinets and islands, any other fixtures in storage or clothing closets. Excessive heat will build up in these confined spaces and may cause cable overheating.
• NEVER install the heating cable under or through a wall, partition, or through a floor.
• NEVER install the factory splice (i.e., black plastic junction between the cold lead and gray heating cable) in the wall. This will cause overheating, system failure, and could cause damage. This splice must be installed entirely under the floor covering, as shown in the heating cable installation instructions.
• It is helpful to plan the location of a buffer zone, as it is not always possible to predict where the heating cable will end. The buffer zone is an area where heating is not essential, typically behind a toilet or adjacent to a door opening. This area allows for the placement of excess heating cable. Heating cables may also be installed 6″ (150 mm) from the wall to create a buffer zone.
• Heating cable testing is required while the heating cable is on the spool and at two subsequent steps during installation to ensure cable quality and for warranty purposes.

Determining Thermostat Placement

Cables have an 11ft power lead that must reach the thermostat location. The sensor wires are 15ft long and must also reach the thermostat location. The thermostat should be placed close to eye level for easy use, not low like light switches.

Subfloor Preparation

To ensure a successful install, you need to start by prepping your subfloor. Follow the key steps below.

Checking & Prepping

• Start by inspecting your subfloor. Check for any signs of damage, cracks, or uneven areas. Repair any damage before installing your DITRA-HEAT system.
• Remove any debris or extra building materials from the area.

• Fill any gaps or cracks with the appropriate filler to create a smooth, even surface.

• If you’re working with a wood subfloor, ensure that the plywood or OSB subfloor is appropriately secured with screws to minimize movement and squeaking. 

Cleaning & Leveling 

• If your subfloor is uneven, you may need to apply a self-leveling compound to provide a level base.
• Clean your subfloor so it is free of dust, dirt, debris, or any other compounds that could prevent the thin-set mortar from properly adhering.

Installing the Membrane

Once you have all your required materials, your layout is planned, and you’ve prepared your subfloor, it’s time to start the installation process. If you are not using DITRA-HEAT Peel & Stick membrane, you need to start with a thin-set mortar. 

DITRA-HEAT & DITRA-HEAT-DUO Installation Steps

1. Begin with mixing up thin-set mortar suitable for your subfloor. The consistency should be fairly fluid, but still firm enough to hold a notch from your trowel. The texture should be smooth and creamy.
2. Spread a layer of thin-set mortar using a notched trowel over the area where the first section of the membrane will be placed.
   1. Tip: If the thin-set mortar skins over before installing the membrane, remove the thin-set mortar and reapply. The thin-set mortar needs to be wet.
3. Press the Ditra-Heat membrane into the wet thin-set, fleece side down. You can use a float or roller to help press the membrane into the thin-set mortar and remove any air pockets.
   1. Tip: Each section of the membrane needs to be securely adhered to the subfloor. Check that there are no voids or bubbles underneath.
   2. Tip: Back-rolling the membrane before application can help prevent the membrane from pulling up from the thin-set mortar.
4. Lift a corner of the membrane to check that there is 100% mortar coverage on the fleece. If there is not full coverage, remove the membrane and reapply the thin-set mortar.
5. Align the edges of adjacent sheets tightly against each other without overlapping. This will create a singular plane for the heating cables.
   1. Tip: Aligning the studs on the top of the membrane will make cable installation easier. 

Continue this process until the entire area is covered with the membrane. Allow the thin-set mortar to cure as recommended by the manufacturer. 

DITRA-HEAT-PS and DITRA-HEAT-DUO-PS Installation Steps

1. Remove the liner from the membrane.
2. Apply the membrane to the floor with the adhesive side down. You can use a float or roller to help embed the membrane to the floor. There shouldn’t be any gaps or air bubbles between the subfloor and the membrane. 
3. Align the edges of adjacent sheets tightly against each other without overlapping. This will create a singular plane for the heating cables.
   1. Tip: Aligning the studs on the top of the membrane will make cable installation easier. 

Continue this process until the entire area is covered with the membrane.

Installing the Cable

After your DITRA-HEAT membrane is installed, it’s time to work on installing the cables. 

Required Heating Cable Tests

These tests need to be done before removing the heating cable from the spool, after the cable is installed in the membrane, and after the flooring is installed. 

1. Test the conductor resistance of your cable. This test is required for warranty coverage. 
   1. Grab your multimeter and set it to resistance measurement.
   2. Place the red lead from the multimeter on the red wire from the heating cable and the black lead from the multimeter on the black wire from the heating cable.
   3. Record your ohms measurement in your heating cable tests log in your Installation Handbook.
      1. If the ohms reading taken varies 10% or more from the value that is printed on your heating cable spool, the cable may be damaged or your multimeter is not set properly. 
2. Test the conductor and ground braid continuity. This test is required for warranty coverage.
   1. Set your multimeter to the continuity test function. 
   2. Test the braid and one of the power leads. 
   3. If there is no continuity, the multimeter will display either “OL” for “overload” or “I” for infinity. This means that the test was successful and there is no continuity. If a value appears on the multimeter, then the test failed. 
   4. Repeat the test with the second power lead.
   5. Record the test results in your heating cables tests log in your Installation Handbook.
3. Test the floor temperature sensors. This test is required for warranty coverage.
   1. Set your multimeter to the resistance setting at room temperature, Ω or 20K Ω +/-2 as applicable. 
   2. Take a reading between the sensor leads. 
   3. Compare the values with the table in your Installation Handbook and record your results. 

Note: You will also see an insulation resistance test in your Installation Handbook. This test is not required for warranty coverage, but it is still recommended to ensure successful installation. Reference your Installation Handbook for further information.

Cable Installation Steps

1. Do all required cable tests mentioned above.
2. Pass the cold lead of the heating cable through a conduit from the bottom of the wall to the thermostat’s electrical box. 
   1. Note: The floor temperature sensors will also get passed through the same conduit as the cold lead or within a separate conduit. 
3. Make a mark where the cold splice will be placed. Then, cut out the section of the membrane (and subfloor if needed) where the cold splice will go. Insert the splice. 
   1. Note: The splice needs to be flush with the membrane so that the flooring can have level installation. 
   2. Tip: Temporarily secure the splice to the floor with thinset or adhesive. 
4. Carefully embed the heating cable between the studs. Make sure to use the proper pattern and spacing determined in your layout plan. 
   1. Note: The heating cables cannot touch or overlap. 
   2. Tip: Leave space for the floor temperature sensors. 
5. Install the floor temperature sensors. They should be evenly spaced between two cable runs, near the middle of your layout, and at least 12 inches into the layout. Mark where the sensor will go on the membrane. Cut an appropriate recess for the sensor. Embed the sensor wire into the membrane. Do not overlap or cross the sensor wire with the heating cable. 
   1. Note: If you’re using a 3-2 stud spacing, then the sensors should be installed in the middle of a 3 stud spacing if your flooring will be ceramic, porcelain, or stone tiles. If you’re using AFCs, install the sensors in the middle of a 2-stud spacing. 
   2. Tip: Remove the heating cable from the area while performing any cuts to prevent accidental damage to the cable. 
6. Retest the heating cables once the heating cables and floor temperature sensors are installed.  

Tip: Take pictures of your floor heating system including cable layout, sensor placements, and splice locations. This can be helpful if you do any future house projects or if you need to troubleshoot. 

Waterproofing

Waterproofing is not required for all applications, but if you need to do it, this is the time in the installation process. For in-depth waterproofing instructions, reference your product’s installation handbook. If you have questions on whether you need to do waterproofing or how to do it, contact one of our team members or call us at 1 905 298 1291.  

Shop Schluter Waterproofing Products

Installing the Flooring

After you have installed the membrane, floor heating cable, and floor temperature sensors, it’s time to install the flooring. Follow the flooring installation instructions for your specific product. 

Note: DITRA-HEAT systems can be installed under ceramic tile, stone tile, vinyl, luxury vinyl tiles (LVT), luxury vinyl planks (LVP), wood plastic composite (WPC), stone plastic composite (SPC) tiles and planks, engineered wood and laminate flooring.