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Commercial Flooring News

UFH – There’s More To It Than Meets The Eye

Martin Cummins on underfloor heating

GIVING recommendations or specifications for flooring installations over underfloor heating (UFH) used to be quite a straight forwards process. The understanding was that UFH was a system that involved a series of pipes encased within a screed, typically 50 to 75mm (depending on the nature of the screed) through which warm water passed.
A knowledge and understanding was built up and a series of questions could be asked to ascertain whether the floor was ready to overlay with a particular floorcovering or smoothing compound. For instance, you need to know whether or not the UFH been commissioned? Is the screed dry? Have expansion joints been incorporated? Will the adhesive line temperature be controlled to less than 28degC?
Over time most manufacturers offered a bespoke specification and conditions needed for when this type of UFH was present.
However, nowadays a reference to UFH can mean a whole new set of parameters needing to be considered. The systems now on offer can include electrical mat or cables on the surface of a screed or a boarded floor.
The type of boarding may be a cementitious faced insulation board, an unfaced board or even plywood. There may be reflective surfaces to direct the heat away from the subfloor and upwards into the room. The system could well have been fitted prior to your arrival and you may have very little knowledge of what is expected.
What temperature will they create at the adhesive line? How much control will the client have on the temperature fluctuations? This type of heating is prevalent for use with stone and ceramic type subfloors and is generally referred to as undertile heating or radiant UFH.
Due to where it originally was aimed it is easily possible to get these systems to generate much higher temperatures which would not pose a problem to stone or tiled floors but could be problems with resilient and timber floors.
An even wider spectrum of UFH systems are warm water systems where the pipes are not encased in a screed but are ‘slotted’ into a grooved out boarded system. The technology and design behind such system, often referred to as retro fit UFH, is changing day by day.
There can be very sound strong gypsum or cement based boards either glued or fixed to the substrate but it maybe that the boards are floating and consist of nothing more than a chipboard construction. There are some designs that incorporate reflective bases also.
There are areas of the subfloor that may be plastic materials which can pose an adhesion problem for any smoothing compounds. The water temperatures are generally not too great on these systems but the question of glue line temperature needs to be asked about and not assumed to be less than the 28degC usually required (for resilient flooring).
So, when looking at technical brochures don’t simply look and see if a product can be used with UFH and then assume it is suitable for all systems. If you have any of the latter two types of system then phone up and speak to the technical departments.
A good technical department will engage in conversation and find out what it is you have, what problems are posed and, where possible, what solutions can be offered. The various substrates will mean consideration for different priming requirements and suitable smoothing compounds as well as minimum and maximum depths of smoothing compound.
Commissioning processes for the systems and use of background heating may be recommended. Product curing and settling times prior to bringing the heating fully on line can be very important.
Adhesive choice for bonded floors will be a key consideration. Advice regarding maximum temperatures can be offered. There is a lot to be considered.
Further help is on its way fortunately. The CFA have put together a cross-manufacture group to put together a working guideline document for UFH.
A great deal of research into available systems is being carried out with the aim to give generic guidance as to what to be aware of and how to approach different UFH systems. Hopefully this will clear the water and perhaps even differentiate the various types of UFH so as to avoid confusion in the future.
So, in summary…. if anything is changing at pace in our industry it is the use of UFH systems. This is in both new build and refurbishment projects. Warm water systems in screeds are generally not too problematic but both warm water retro fit systems and electrical radiant heating offer significant technical challenges for both the flooring contractor and the manufacturer of flooring products.
Only by communication can you ensure the correct recommendation so do your research before the job to ensure that the lovely floor you have fitted isn’t going to need to be uplifted again.
Martin Cummins is Ultra Floor technical sales manager

T: 01827 871871

This article has been reproduced from the Contract Flooring Journal website. You can find them at