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Alternative to the heated towel rail, the low temperature electric floor allows to obtain very quickly an excellent comfort without big jobs.

Floor heating and tile from above in a bathroom

Difficulty: 2/4
Cost: about 400 € (excluding tiling)
Time: 3 days
equipment: scissors, screwdriver, trowel, notched trowel, sponge, paint roller, electric tester, screwdriver, hole saw, grinder, tile, grooving machine...

There are two solutions for heating a bathroom: the classic radiator - but the floor stays cold - or a floor heating system. In renovation, equipping the entire house with a heated floor is certainly powerful but expensive. On the other hand, it is possible to efficiently heat a body of water without carrying out heavy work, by opting for low temperature heating by the ground.

Low temperature heating: a comfortable extra... and adhesive!

The system selected on this site ("Comfortmat STE" by Deléage) temporarily alleviates the feeling of cold soil (it is not a central heating!).
It consists of a self-adhesive fiberglass mesh 50 cm wide, on which is attached a shielded heating cable (diameter less than 5.5 mm). The process is based on the integration of this heating element into the tile adhesive.
The adhesive weft sticks directly on existing tiles after the application of a primer. The coating of the heating elements requires the use of a flexible adhesive mortar (type C2-S1 / S2, Weber, Parexlanko or PRB) that resists deformation related to heating.

Lay an electric heater on and under tiles: heater

1) New coating
2) Adhesive mortar
3) Heating frame
4) Existing tile

Individual control of a floor heating for bathroom

The system is associated with a wall-mounted electric regulator proposed by the manufacturer and connected to a floor sensor. It has a timer adjustable up to 2 hours.
For safety, the regulator must be installed in the bathroom area more than 60 cm away from the shower and / or the bath, in accordance with the regulations (NF C 15-100). It must be connected to a 30 mA differential circuit breaker on the electrical panel.
When connected to a thermostat with a protection rating (IP) of less than 30, it must be installed outside the room.

Heating frame: soil preparation before laying

Prepare a floor for laying a heating screen

  • In the empty room, after marking and tracing on the ground, make 2 grooves to the grooving machine: one for the cold connection connecting the thermostat to the heating cable, one for the temperature sensor.

Install a floor heating thermostat

  • Using a 67 mm diameter hole saw, cut out the recess box housing of the thermostat.

Connect a floor heating to your thermostat

  • Run the corrugated ducts through the bulkhead from the thermostat location to the bulkhead and into each groove.

Fix the cable ducts of a floor heating

  • The sleeves must remain in position.
  • If necessary, place dots of PU glue (Pattex, Bostik) at the bottom of the groove to hold them.

Prepare the installation of a floor heating: the primary

  • After checking the surface condition of the substrate (flatness, cleanliness, asperities) and, if necessary, make a patch *, apply a layer of primer to the roller. It promotes the adhesion of the adhesive mortar.
* Patching is unnecessary if the ground flatness gap is less than 7 mm under a 2 m mason ruler.

Info + for laying tiles on underfloor heating

Glue large tiles

Double sizing can sometimes be tricky, especially with large tiles.
In this case, it is possible to coat the heating weft with the mortiercolle (spatula notched and smooth) and, the next day, to perform the actual laying of the flooring with a simple glue (unless otherwise specified by maker).

Setting up a heating plot

Laying a heating screen: the cables

  • Insert the cold connection into the dedicated duct.
  • Retrieve the end at the flush-mounting box of the thermostat.

Laying a heating screen: useful areas

  • Unwind the heating screen according to the layout and manufacturer's instructions.
  • It only covers traffic areas.
  • It is forbidden to place under the bath, furniture, etc.

Heating frame in a bathroom: installation tips

  • Continue the pose.
  • Unroll each self-adhesive tape by gently flattening it to the ground to obtain a homogeneous surface.

Heater for bathroom: how to cut

  • Cut the weft to the desired length using scissors, to orient it differently if necessary.
  • Be careful not to cut or crush the heating cable (red).

Position a heating screen

  • Spread the weft over the entire surface (without overlapping or crossing expansion or splitting joints).
  • Record on the installation plan (provided), the heated surface dimensions relative to the partitions and the location of the cold connection and the probe.

Powering up a heating screen

  • Cut the excess cold link at the thermostat.
  • Connect it to the control system, then turn on the power.

Test the resistance of the cable of a floor heating

  • Using an electrical tester, check the resistance of the cable and the good insulation of the frame.
  • Post the data on the warranty card.

Laying tiles on a floor heating

Spoil a floor covered with a heating screen

  • Mix an adhesive mortar (class C2-S1 / S2) and cover the heating screen with a 10 mm notched trowel.
  • Move the comb in the width of the frame.

Glue a floor to be tiled on a floor heating

  • Establish a layout plan and begin laying the tiles in the most visible corner of the room.
  • Glue the back of the tiles with the mortar.

Gluing door profiles before tiling

  • After cutting to the desired width, glue the door profiles (or nosing steps, etc.) with a trowel.
  • Their height must be equivalent to the thickness of the mortar + tile.

Lay an electric heater on and under tiles: heater

  • If the straight cuts can be made easily with the tile, others, more complex, require a grinder equipped with a diamond disc.

Lay an electric heater on and under tiles: heating

  • Continue sizing by regularly cleaning the tiles with a damp sponge.
  • Then grout with a special joint mortar (Bostik, Sika, Weber).

Heating of a floor equipped with a heating screen

  • Perform the first heat up after complete drying (one week) or, ideally, after all finishing work (wall, floor, ceiling and furniture).

Supplies for laying a heating screen and a bathroom tile

• 5.55 m frame with 337 W heating cable, cold connection, probe
• Thermostat
• Recessed box
• Tile primer, mortar and tile joint mortar
• Floor finishing profiles
• Floor tile


Video Instruction: How to install underfloor heating and tile with large porcelain tiles