Should I Install Floor Heating under the screed bed or directly under the tiles?

Generally, your heating can be placed under a screed bed if the bed is to be less than 40mm thick, or on top of the screed bed to sit just under the tiles. Both will work nicely, but will just perform a little differently, as the screed will act as a thermal mass, storing the heat. With the heating positioned under the screen, it will take longer to heat up and cool down, however, a good result is achieved as the thermostat and in floor temperature sensor will adjust and regulate the floor temperature accordingly.

Temperature changes at different times of the day are more effective for heating installed directly under the tiles. Faster response times are due to the heating having to heat through less material before reaching the surface.

In summary, both methods work well and are recommended installation options. Personally, I have 3 heated bathrooms in my own home. Two heated areas are under screed, and one is under tile. The difference in performance is not noticeable, and they all work flawlessly. The thermostatic controllers adjust the temperatures accordingly and provide a beautiful warmth to the bathrooms.

Other Considerations
Generally, on larger building sites or developments, under tile heating is placed underneath the screed bed. This is due to a higher risk of damage with several trades people working on a building site. In this case it is an advantage to cover the heating with a sand & cement screed bed before the tiling commences.

Avoiding Damage to Floor Heating while screeding
The main culprit in damaging heating after it has been installed is from wheelbarrows being run over the heated area while screeding. This is especially common if a large area has been heated and the screeders are using wheelbarrows to transport the sand cement mix. If possible, use buckets of screed, or make a “track” for the wheelbarrow over the heating with core flute or similar. The corflute track can then be repositioned as necessary as the screeding process is completed.

Advantages of under screed heating

  • Your floor will retain heat longer if the floor heating is installed under the screed bed.
  • The heating cannot be damaged during tiling, if the screed bed has been installed first.
  • If a tile needs to be replaced, there is no risk of damage to the heating element.

Advantages of under tile heating

  • Your floor will heat up more quickly if the floor heating is installed directly underneath the tiles.
  • The floor temperature can be regulated up and down more effectively at different times of the day.
  • The temperature sensor is closer to the tile giving a more accurate floor temperature.

Which Heating product should I use?
Custom Heat under tile heating mats are designed for both under tile and in screed installation. Our mats are 3.8 mm in thickness which makes them thin enough to sit within the tile adhesive, whilst they are also powerful enough to heat through a 40mm sand cement bed. If you have a bed greater than 40mm we can upgrade the heating cable to suit your application. Just give us a call!

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