Thanks for your quick response. Re-Tiling is a more time consuming and expensive option for me. I just want my extension to finish. Although the builder will remove all the tiles but I will have to pay for the tiles and tilers. Do you this UFH will work if I go for Laminate over tiles

I agree with Matthew, a professional would realise sooner his mistake and correct it straight away.

If he doesn't want to pay, just remind him he has insurance, otherwise what is the point of having it!

I could have suggested to use Porcelain tiles which we supply they are 4 mm thick so very thin tiles, they would still conduct heat etc........, but there is no point adding to someone mistake trying to rectify it.

Best way is always to do it right as it should has been done in the first place.

just one more thing make sure that whoever does the tiling will agree on whatever surface he will tile onto, so the tiler everything first so he want have any complaints later.

Thanks guys, I really appreciate your help. I will try to get the builder to fix it. Just so that I know Will UFH be effective with one more layer of either 4mm Porcelain tiles or laminate. Basically I am preparing for the worst here. In case the builder just doesn't want to do anything, the cheapest option for me will be to get another layer of flooring on top.

I fully agree with all comments along the lines of getting the builder to put it right at his own cost... To answer your other question though, if you do end having to go for laminate flooring (which would be a pity), the underfloor heating WILL still work so you don't need to worry on that score. Just be a bit careful what type of underlay the installer uses -you don't want it melting, nor do you want it to prevent the heat passing through it. A competent laminate installer should be aware of what type will work with UFH coz it's not at all uncommon.

Have you paid him? If not, trading standards will give you advice on how to proceed.