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Builder Comes Unstuck After Fitting UFH

John Alcock on getting it right first time

A RECENT technical support job reminded me of the importance of using the right contractors for flooring projects – and perhaps also how the skills and experience of flooring professionals can sometimes be undervalued when there is a desire to get a job done quickly and with minimal costs.

A builder had called up for some advice on what smoothing compound to lay with a new underfloor heating system he was fitting himself.

Duly informed, the chap went away and purchased the fibre-reinforced underlayment as recommended, but rang back a while later as the tiles he laid had begun to rise and come away from the floor. It sounded very unlikely for this to be a problem with our smoothing compound, so I visited him to investigate further.

The site was a bungalow being renovated to a pretty high standard, hence the underfloor heating system. What immediately struck me was that his flooring installation was ‘alternative’, to say the least.

Keeping the existing floorboards and the usual air gap beneath, he had then fitted chipboard over them. Above this he had put down the standard grid system, into which he had installed the underfloor heating pipes. Over that he had then directly put down our smoothing compound. The finishing had been applied without primer – apparently he was advised elsewhere that primer was not needed.

To my mind the problem was simple: The floorboards were moving due to the shifts in temperature caused by the new heating system. This made for an unstable surface on which to fix the tiles, especially given that no primer had been used.

So they had begun to move and come away when the heating was switched on. Our smoothing compound was a blameless victim caught between the tiles and the moving floorboards.

The upshot is that the builder is facing the prospect of installing an entirely new floor – this time one that isn’t prone to moving whenever the heating system is switched on or off.

I dread to think of the cost involved in doing that. The whole unfortunate situation highlighted to me the danger of cutting corners on flooring jobs, and of making sure that those actually doing the job have the knowledge and skills to get it done right first time.

I don’t just mean this in regards to my hobbyhorse of not using primer, but also given the popularity of components like underfloor heating – although I am a fan – make the challenge of fitting a floor more complicated than in the past.

It’s tempting to think that there is a perception that fitting flooring is an easy job, or at least that you can save money on a project by not employing a flooring professional.

Clearly, and on this evidence especially where a pricey refurb job is concerned, it pays to make sure you have the right skills and experience on site to get things done right the first time, without making expensive mistakes.

John Alcock is technical specifications manager at Bostik

T: 01785 272727

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