Hi Scott, thanks for your question.
Tiling onto under floor heating or under tile heating systems may sound like a project too far – but fear not, with the right selection of tile adhesive, grout and other products your installation can be a success.
We would always recommend the use of an uncoupling mat system like Dunlop Pro Cover. Laid easily on top of your heated screed with a flexible tile adhesive, the mating provides a buffer layer between the tile and the substrate and helps prevent any cracking or de-bonding of the tile due to the different rates of expansion and movement experienced by the tile and substrate.
While new cement-based screeds and adhesives can expand at different rates to each other, this can cause stresses to build at the interface between tile /adhesive and the screed – causing the weakest part of the system to break, in this case the tile.
A flexible cement-based tile adhesive such as Dunlop Flexible Rapidset Floor and Wall Tile Adhesive is an absolute must when tiling on top of under floor heating or under tile heating. Flexible tile adhesives are modified with polymers which help the adhesive bend and move with the substrate and react to any expansion/contraction from the heated screed.
With this in mind, always use a flexible floor & wall grout such as Dunlop GX-500 Flexible Grout, to further protect against any lateral movement.
If tiling onto electrical under-tile warming mats, the use of Dunlop levelling compound is ideal to level over the cables such as Dunlop LX-360 Fibre Leveller. Simply pour the compound over the cables, making sure you cover them all and this will help guard against any accidently damage to the wire when using a floating trowel.
Once the leveller is dry after 2 hours, you can use a flexible cement based adhesive such as Dunlop Large Format & Natural Stone Adhesive and flexible grout such as Dunlop GX-500 Flexible Grout.
One final tip: don’t turn on the heating system to early it can weaken the tile adhesive and grout. If the adhesive is allowed to dry out before it has properly hardened it will become weak and crumbly. It’s important that the heating system is turned off before tiling, and remains off until the adhesive and grout is fully cured, minimum 2 weeks after tiling is finished and follow manufactures instructions on swiching on the heating system.
Want more tiling advice? Take a look at the Dunlop Blog (DunlopMan Blog) – here we take some of the best tweets we get, and turn them into helpful tips and advice.