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TTA provides UFH advice for tilers

There has been a surge in interest in underfloor heating systems (UFH) in recent years, as knowledge of the benefits and ease with which UFH can be installed has evolved. Industry estimates indicate that the market has been virtually doubling annually in recent years. It is not difficult to appreciate why this is the case, since UFH provides a cost-effective, comfortable and unobtrusive heating solution.

Its use enables building designers to meet modern energy efficiency regulations, reducing the carbon footprint of buildings and allowing for the implementation of contemporary design concepts. Homebuyers may also look at underfloor heating as a point of difference and a good USP on the resale market. The use of UFH with tiling transforms what is traditionally viewed as a rigid and cold surface, into a warm and welcoming environment.

UFH installations are increasingly tied to renewable energy sources, because of the lower running temperatures of the technology, and this concept appeals to consumers who aspire to a zero carbon house, as well as those who just want to reduce their fuel bills. It therefore seems certain that the UFH will continue to grow in importance.

For homeowners, the latest innovations mean high comfort levels, consistent temperatures and greater cleanliness, coupled with low running costs, because the systems tend to employ large surface areas heated to a lower temperature. The installation cost of UFH in new build is comparable to a standard radiator system but it can provide 30% greater energy efficiency compared to traditional space heating.

So these systems have become a mainstay of modern house construction, and there are two different types to consider. The first category comprises electric matting systems, installed directly under a tiled floor and which are therefore laid as part of the tiling process. The second group is made up of warm water (wet) systems, which are installed within a screed. Installing electric UFH is less disruptive than a warm water system and more suitable for small scale – less than 20sqm – installations, like bathrooms. However, an electric system tends to be more expensive to run when compared with warm water UFH – as a general rule 30-40% more.

Warm water is ideal for installation in new build, complete renovations, extensions and large areas in general. It can be linked in to an existing radiator system and most effective when installed with alternative energy sources such as geothermal or solar.

The installation of such systems, particularly wet systems, is not however always problem-free. Historically, cracked tiles were associated with heated floor construction. Inappropriate tiles or adhesives used on equally inappropriate substrates would result in weakness or fragility. Surface deformation, resulting in tenting and debonding, or cracks in the tiled surface covering, can be caused by the different rates at which different materials expand when heated.

Also, if expansion joints are poorly positioned, problems will arise when the different elements of the floor assembly move at different rates. Of course, quality of workmanship can also be an issue.

Since ceramics and natural stone are rigid finishes that will not deform laterally when they are bonded directly to the heated screed with adhesives – intermediate movement joints are essential.

This requirement applies for all types of rigid screeds including cementitious and calcium sulfate based screeds.

The provision and detailing of intermediate joints should be considered at the design stage and the thermal movements of the substrate assembly should be taken into account.

There are a number of areas that installers need to look out for in order to avoid problems. TTA has released a technical document entitled: ‘Tiling to Heated Floors’. As with all TTA Technical Documents, members are able to download these free of charge, and non-members can purchase them either in PDF or paper format.

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