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Short Summary
Main recommendation: install the Schluter Ditra Heat cable system as a combined uncoupling membrane and electric floor heating layer under tile, bonding the mat to a clean, wet subfloor with non-modified thin-set. The video also recommends buying the cable and thermostat together, since the sensor cable comes with the thermostat and must be embedded before the tile goes down.
Key Points
- Ditra Heat is an uncoupling membrane with heating cable pre-installed; the presenter says it protects tile from cracking if the structure expands or contracts at a different rate than the tile, which is why it is used on outside walls.
- The presenter says the mat can be walked on right away, so tiling can start immediately after it is laid, provided only a light amount of cement is used.
- Heating cable is sized by the area to be heated, not the room size: the cable is run about five inches off walls and kept about two feet back from a vanity.
- The presenter notes the system can double as part of a floor waterproofing system when used with Schluter Bond tape, though it was not used that way in this build because heat runs through the floor.
- The presenter says the installer should record the cable's electrical resistance (in ohms) before installation, after installation, and after tiling, then send the records to Schluter.
Details Worth Noting
- Concrete instructions:
- Clean the subfloor thoroughly, removing debris and screws, and make it wet (not dry) before installing.
- Wet the wood subfloor so the cement bonds better; the presenter says the longer the cement stays wet, the better it adheres.
- Spread non-modified cement with the Ditra trowel, using a small notch ("less is more"), and comb it out so the mat can be pressed into it.
- Lay the mat and apply a moderate amount of pressure; double-check adhesion if desired.
- Line up the mat sections so the heating cable can be interwoven into the spaces, keeping lines relatively straight.
- Buy the cable and thermostat at the same time, and embed the thermostat's sensor cable during installation, not after tiling.
- Snap the sensor into place; the lead wire is long enough to reach the thermostat from an inconvenient location.
- Measure the area to be heated, keep the cable about five inches from walls, and avoid running it under cabinets or the toilet.
- Use a rubber float (not a metal trowel) to press the cable into the grooves.
- Turn the cable corners about two feet before the vanity (the vanity used was 21 inches) so toes do not get cold.
- Space the cable every three inches (three octagons apart) since this is a floor-warming system, not the primary heat source.
- Test resistance with an ohmmeter (about $20 at a hardware store): the value on the package was 29.6 kilo-ohms, so the meter reading (times 1,000) should be close to that. Record it before install, after install, and after tiling, and keep the records for Schluter.
- The presenter says heated floors can also be run in a shower pan, with cable set in hot glue and tiled over; Schluter reportedly was not against this if installed properly, and the presenter says it helps shower floors dry out and reduces mold, mildew, and hard-water rings.
- The presenter notes the warranty card must be filled out with the certified installer's personal information, since he is a certified installer.
- The video is a single installer's walkthrough; no cost, tile type, or general electrical code guidance is given.
Bottom Line
Ditra Heat combines an uncoupling membrane and electric floor heating, and this video shows that the key to a successful install is preparing a clean, wet subfloor, embedding the sensor and thermostat up front, and recording resistance readings for the warranty.
