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UFH and wooden flooring: it's all in the preparation!

Last week we received a question from a rather frustrated home-owner:

"Hi, I am having trouble in getting my floor leveled. Got the builders to remove the floor joists and lay concrete layer. I went on holiday post this and when i returned, builders suggested this was topped with insulation, and then followed by the UFH pipes. They say it was then topped by Latex screed, which by the time i came back was very unleveled and had cracks all over.

To get it to level, builders use self leveling compound wherever it was needed (in large parts), but to my dismay just after 10 days, the floor has started cracking and unleveling again because of these cracks.

I am so damn frustrated with all this leveling thing, and we have already got the engineered wood we want to lay on top of it. But my floor layer says, if he lays the wood on top of this floor, it will move quite a bit and be wobbly and also showed me the movement by placing a few pieces together.

I have no clue as to what we should be doing now, even though builders are very nice i guess they are clueless as well. They are thinking of topping it with another layer of some kind of mixture, and I am just concerned that with 2 layers already on top of UFH, a third layer of a compound, which if everything works ok will be topped by engineered wood - which will make the UFH pretty useless or extremely expensive to heat up the floor in my view.

Would you be able to advice what you think we did wrong and how can we get our floor to be leveled so the wood floor doesn't wobble and UFH remains effective too.

Thank you for your question and sorry to hear about your problems. However, very glad to read that your wooden floor fitter refuses to install the wood floor on this crumbling underfloor, 'cos he's absolutely right.

If the crumbling layer is patched up again your UFH system will never work properly - as I fear it will not do this anyway at the moment due to the cracks (patching up solutions on patched up solutions never works!)

A floor can be unlevel, but only 3mm maximum over 1 meter and only in one direction. Presumably your fitter plans to fully bond the floor to the concrete with flexible adhesive and if the floor is too unlevel (dips and hills) this will never work: there will be air-gaps underneath the wood everywhere, rendering your UFH system useless indeed.

I'm afraid you have to re-call your builders and tell them to start over with the screed - preferably back to the insulation. Your concrete/screed ontop of the UFH needs to be smooth and whole (no cracks!) in order to work and in order to provide a proper surface for your wood floor fitter.

Sorry we don't have better news for you and I recommend you also get advice from the manufacturer/supplier of the UFH system.


An installation of a wooden floor starts with the correct preparations, especially when there is new concrete or screed involved. Like in the case above, when you also add Underfloor Heating to the fro - a sound, dry and level concrete/screed surface is even more important. A defect surface will definitely mean a defect or at least inefficient working of the UFH.

Always get advice from the supplier/manufacturer of the UFH system about the correct preparations, follow this (have this followed by you builder) and prevent aggravation, frustration and extra costs and/or delays.

And never accept patching up solutions, no matter how nice or hard working your builder seems: it is bound to end in tears.


If you are thinking of using Underfloor Heating and install a wooden floor, request our start-up tips here.

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