Underfloor heating and tiling

28 Nov 2005
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United Kingdom
Hopefully someone can help me on this one - I've been asked to tile a bathroom floor that has been fitted with underfloor heating. Normally I'd put a screed on top of matting and then tile onto this. However the underfloor heating matting has been laid on top of what appears to be some sort of under mat, about 10mm thick made of foam (I think).

My question is should I still screed and then tile as usual or is there something else I should be doing, I'm worried that even with the flexible screed/adhesive that the matting underneath the ufh will compress a cause problems later on. Can anyone offer some advice.

Another question -to save on screeding is it ok to fix floor tiles with extra adhesive straight onto ufh. Sorry if this seems an obvious question but I need to get this straight in my head :eek:

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Lots of info on the klima and warmup websites. Or pick up one of the warmup booklets from tile shops (Topps have them on the counter) which are really informative.

The 10mm insulation board if layed on a flat surface has very high compressive strength, and can be tiled straight onto, over the heatmat. Just be very careful with your trowel, if you damage the mat you certainly won't be on their christmas card list! Some would say use a plastic trowel or spreader to be on the safe side.

Make sure the mat is firmly fixed down before you start, with the correct mesh tape. (Looks like, and probably is, drywall tape)

I had to lift some vinyl tiles which had been laid on UFH (you could see the layout of the heating cable burned into the top of the vinyl tiles :eek: ) the matting had been stuck down with gaffa tape with levelling compound over the top
When pulling up the tiles long strips of the screed came up with it as the silver part of the gaffa tape had melted away from the backing, leaving the screed not stuck to the deck, and the cables exposed. (In the end I managed to patch it up and lay proper tiles on top.)

Words of warning!

Make sure the insulation board has been securely fixed down as per instructions. Special screwed fixings for timber, flexi adhesive for concrete.

Do you know what is under the heating mat? A crappy subfloor could still give you cracked tiles.

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