High temperatures and their impact on flooring

Martin Cummins

Published by Martin Cummins - UK Technical Support Manager, Bostik

Martin has been involved in the industry for over 20 years. He’s passionate about flooring in all its guises, with his particular expertise being in subfloor preparation products and adhesives. Martin is an active member of the CFA manufacturers committee and he sits on the CFA council. He aims to keep abreast of all the changes in the industry and feeds this knowledge back to installers to make sure when floors are laid they perform to their maximum potential.

Although the flooring industry is a very well established one, it does move with the times. For example, over the last decade we have seen an upsurge in the use of underfloor heating (UFH) systems with all the inherent benefits they bring. UFH in itself is not particularly problematic for flooring installations, but there are still a few pointers to be aware of when it comes to the effect that temperature can have on flooring installations.

So, what are the concerns? The short answer is that the problems are more to do with temperature variation or fluctuation, rather than floors being particularly warm or cold.

With manufacturers bringing out an increasing range of design floors (loosely referred to as LVT or luxury vinyl tiles) to mimic timber, ceramic tiles etc., there is a much greater scope for flooring. When such floors are used in conservatories, atriums or indeed in front of patio doors or glass fronted corridors and shop fronts, the effect of temperature can be very significant.

Any material is prone to dimensional change when subject to temperature variation. The greater the variation, the greater the dimensional change. Some products, and in this instance I am referring to LVTs, are extremely strong so any attempts to change dimension will be very hard to stop.

The biggest concern is with a conservatory, where the glass works to radiate the sunlight to greatly raise both the air temperature and the temperature of the fixtures and fittings, including the floor. However, in the evenings or on cool days the temperature will drop, meaning the floor temperature can easily fluctuate from 40oC down to 5oC, even on the warmest of summer days. This may also be the case with patio doors, atriums and glass fronted shops or corridors.

Another area of concern is with radiant underfloor heating systems, i.e. electric mat type systems. The ability to switch these on and off at ease coupled with the fact that the home owner is unlikely to be a flooring or scientific expert means they can sometimes be abused, with temperature fluctuations being applied very quickly.

Finally, warm water underfloor heating also has to be considered. These systems are generally designed to produce a floor temperature comfortable to walk on and this, for the flooring industry, should mean no greater than 28oC at the glue line. Traditional warm water UFH systems will find it difficult to suddenly raise temperatures. However, the newer design of warm water UFH, with pipes in grooved boards, may present more of a risk as they will rise in temperature more quickly when switching from off to full temperature.

It is important to appreciate that UFH systems were generally designed to make cold floors such as stone, ceramic etc. warm, and these materials themselves have very low thermal expansion rates compared to modern floor coverings. However, UFH systems are now often used as the primary heating source in many new builds.

So, what is the answer?
Historically very hard, solid curing adhesives such as epoxy or PU products have been used to “anchor” flooring in place. These adhesives are not easy to use and take a significant amount of time to build up bond strength. If the flooring starts to shrink or expand during this curing phase the floor will set in that position, i.e. with gaps or ridged up. The mechanical stability of such adhesives is part of the reason why they have traditionally been the default, but nowadays technology has moved on to offer easier to use alternatives.

The adhesives designed for such situations are often referred to as high temperature or HT adhesives, but this isn’t strictly true as to their benefit. Most flooring adhesive will work at a high temperature, or at a low temperature, or at a mid-temperature – the key is performing consistently across the range of temperatures. Modern polymers can offer a combination of good ‘trowelability’, reasonable open time and exceptional dimensional shear resistance over temperature ranges.

These are the products you should be using every time in a conservatory, or near glass fronted doors, corridors etc. and they should also be considered with radiant UFH. They may require extra consideration when bonding LVTs, so always follow the instructions.

HT adhesives won’t be suitable for dry stick pressure sensitive use, (indeed LVT should never really be laid on a full dry stick application), and you may have to work on smaller areas at a time to ensure wet bonding is achieved. The wet bond is key to ensuring cohesion between the back of LVT and the subfloor. The bond strength builds up quickly as soon as the materials are bonded and will increase over the next 48 hours or so. It’s still beneficial on hot days to black out conservatory windows for this period and definitely keep the UFH at a constant temperature during installation. You can still use your favoured LVT adhesive on the rest of the floor where temperature fluctuations aren’t a concern.

All in all, technology in adhesives has moved forward to accommodate design changes and areas of use and continues to do so. This is what makes flooring such an interesting industry to us technical bods. So, when I hear the old adage of, “I’ve been doing it this way for thirty years”, I raise a smile in the knowledge that so much has changed in that time, meaning that doing it a certain way for thirty years is far from a claim of proficiency.

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