Schluter Technical Manager Ian Knifton looks at ways of protecting tiles from damage, when fixed over underfloor heating

Underfloor heating systems have no visible heat emitters such as radiators to disfigure walls, and they generate gentle, controllable heat while offering low running costs, special precautions must be taken to counter the effects of thermal expansion and contraction.

The current boom in underfloor heating is bringing its own set of problems for tiling contractors and specifiers: temperature changes within the screed mass of underfloor heating installations -- whether water or electric – lead to the screed moving at a different rate from the tile or stone surface. The rigid surface simply cannot cope with the degree of movement, and the tiles split or debond.

Underfloor systems are increasingly being recognised as an ideal way to warm a variety of rooms, both in domestic applications and commercial buildings. They have no visible heat emitters such as radiators to disfigure walls, and they generate gentle, controllable heat while offering low running costs.

But all too often they are fitted without sufficiently protecting the tiles from movement. Frequently just flexible tile adhesive is used, which doesn’t always provide a total solution against the range of movement caused by underfloor heating. Therefore, special precautions must be taken to counter the effects of thermal expansion and contraction.

Schluter has had numerous enquiries from tilers who’ve been wary of fixing over heated screeds because of problems they’ve experienced in the past, and from contractors called in to undertake remedial work.

If a “traditional” fix is required, where the tiles were originally installed directly onto the substrate, most problems can be overcome by using an uncoupling membrane such as Schluter-DITRA to neutralise the differential movement between the substrate and the surface. It will also bridge and neutralise any cracking in the substrate.