Water-based underfloor heating with tiles

Laying tiles directly on the Flooré underfloor heating

In dry room spaces, tiles can be laid directly on the Flooré underfloor heating. Flooré floor panels should be glued to the subfloor, regardless of the type of room space. A more detailed description is given below of how this should be done.

The laying procedure, system solutions and requirements vary according to the type of room that the underfloor heating will be installed in. In this case, a differentiation is made between dry room spaces and wet room spaces. Wet room spaces refer to rooms where the joists are fitted with a moisture barrier (they very often have floor drains), for example, bathrooms, washrooms, and in new boiler rooms. In wet room spaces, industry rules require a layer of leveling compound (screed) and reinforced mesh on top of the system.
Read more about Water-based underfloor heating in bathrooms

It is time to lay tiles on the water-based underfloor heating

When the underfloor heating system has been installed and the pressure has been tested, it is time to lay the tiles. The underfloor heating system must be turned off, in particular when laying tiles, as the temperature affects the tile adhesive’s and grout’s drying time and, therefore, long-term properties.
Please note that these are only general recommendations when laying a surface layer. If there is a discrepancy between these general recommendations and those of the supplier, follow the instructions of the manufacturer of the surface layer or accessories.
Make sure that the underfloor heating is:

  • Level and dry
  • Clean and free from any floor and other residue
  • The floor panels must be firmly affixed to the subfloor. If a panel is loose locally, wobbles or makes any noise against the subfloor, secure it further with screws or similar

To lay tiles directly on the underfloor heating, the joists must be stable and there must be no defect in the design. Movements of the joists can cause, for instance, cracks in the joints or the tiles to come loose at a later stage. In general, the installation procedure is as follows:

  • Wipe clean the floor surface with methylated spirits to remove dust, oil, grease, etc. from the surface. Don’t use solvents as they may abrade the cellular plastic.
  • Apply primer according to the supplier’s instructions. The primer must be applied undiluted, unless otherwise indicated in the product manufacturer’s instructions. Use only the product recommended by the manufacturer according to the table. Not all primer types work on aluminum foil. Make sure that the primer disperses and covers the whole surface area. Puddling must not occur. Allow the primer to dry as specified in the instructions.
  • Mix the tile adhesive according to the manufacturer’s instructions. Use an appropriate adhesive spreader (this depends on the size of the tiles, patterns on the back, etc.). Start by laying a few tiles as a trial. It should be possible to spread the tile adhesive without it running again (in which case it is too wet) or forming lumps (in which case it is too dry). Lay a couple of tiles and take them up – the back of them should be completely covered with tile adhesive.

Tile size

The tile adhesive combined with the tiles distributes point loads. However, the tiles should not be less than 15 x 15 cm. For smaller tiles or a mosaic, a load-distributing board or a layer of fiber-reinforced screed should be applied on top of the heating system. Leveling compound can also be used on top of the Flooré flooring to strengthen the subfloor before any tiles are laid.

Tile adhesive

The tile adhesive you choose is influenced, on the one hand, by the stone material which the tiles are made of (e.g. slate and marble may be sensitive) and, on the other, by your experience in laying tiles and how soon you can walk on the floor after laying the tiles. Before you choose a tile adhesive, the following words may appear in connection with the products:

  • Pot life – The time the tile adhesive is on the roller (in the bucket), from being mixed until becoming unworkable.
  • Wet-edge time – The time you have to lay tiles once the tile adhesive has been spread over the surface.
  • Adjustable – The time during which the tile can be readjusted, calculated from when tile adhesive was applied to it.

The size of the adhesive spreader’s teeth depends on the size of the tile. Ask your tile supplier what the appropriate tooth size is. An 8 mm spreader is usually used, but it is the tile’s properties and dimensions that determine the choice. Always use a mixer when tile adhesive or grout needs to be mixed.