Underfloor heating under tiles and uncoupling membranes (Ditra)
Tile is a good surface over underfloor heating because it conducts heat well, but the floor moves as it warms and cools. An uncoupling membrane such as Ditra sits between the substrate and the tile, absorbing that movement so it is not transferred into the tiles and grout as cracks.
What does an uncoupling membrane actually do?
It separates the tile layer from the substrate. Timber and screed floors move with heat, moisture and load, and tile does not. The membrane lets the two move independently, which is why it is used over underfloor heating, new screeds and timber floors rather than being an optional upgrade.
Do I need Ditra under every tiled floor?
No. On a stable, dry, well-prepared concrete floor a good adhesive on a primed substrate is often enough. It earns its place over underfloor heating, over timber and chipboard floors, over young screeds and where movement or cracking is a known risk.
What is the build-up over underfloor heating?
A typical tiled floor over heating is built in layers, each one dependent on the last:
- A sound, level substrate — concrete, screed or an overboarded timber floor.
- The heating system, whether electric mat or wet pipework, installed by the relevant trade.
- Levelling compound over the system where required.
- Uncoupling membrane, bedded fully with no voids.
- Flexible adhesive and the tile, then flexible grout and movement joints where needed.
Why do tiles crack over underfloor heating?
Usually because the floor was tiled rigidly onto a moving substrate, because movement joints were left out at perimeters and doorways, or because the heating was turned on too soon and dried the adhesive unevenly. The tile itself is rarely the problem.
When can the underfloor heating be switched on after tiling?
Not straight away. Adhesive and grout need to cure first, and the system should then be brought up gradually rather than put straight to full temperature. Follow the heating manufacturer's commissioning instructions, and if the screed is new it also needs its own commissioning cycle before tiling.
Which tiles work best over underfloor heating?
Porcelain and ceramic are the usual choices because they are dense and stable. Natural stone and marble also work well but move more with temperature and need suitable adhesive and joints. Check the tile is approved by its manufacturer for use over underfloor heating.
Does TLS Tiling install the heating itself?
No — we do tiling only, so the electrics and plumbing for the heating are handled by your electrician or plumber. We take over once the system is installed and tested, then level, install the uncoupling membrane and tile over it.
How TLS Tiling can help
We tile over underfloor heating across London and around twenty miles out, including Ditra uncoupling membrane installation, with over ten years' experience and an NVQ in tiling. Tell us what heating system you have and send photos of the floor for a free quote.
Related services: Floor tiling, Natural stone tiling, Bathroom tiling.