Tile Underfloor heating.

Oct 20, 2006 6 Replies

I am going to tile our hallway, downstairs loo and kitchen with porcelain tiles and thinking that underfloor heating would be a nice addition also. The plan of those three, lends itself to a continuous run and is probably about 10 sq m in total size. though the long hallway, Im thinking only really the middle of the passage needs heating - and not really needing of up and down runs.



Just a couple of simple questions....


Firstly, the surface. The floor itself the tiles are to be laid on, is from the original building floor. Its not concrete - but a plasticy type tile that is often seen. Ive got no idea of its depth, but would say its probably about 2 or 3mm.



Does that sound likely to be ok for using underfloor heating with? I dont think the tiles mentioned are plastic (which would obvioulsy be likely to melt under an electronic element), but that about the best description I can think to describe them. I am unable to lay boards to insulate further. It would raise the level too high.



My second question is related to wiring and the sensor probe Ive seen mention in these kits. They talk about digging down to fit the probe, whilst the heating elements themselves, are just sticky taked into position, then tiled over. Im confused as to why you would dig down? Is that just because of its bulk - which would be much higher that the rest of the elements? Im assuming that to be the case - but dont like the idea of cracking the current plasticy flooring thats in situ.



Lastly, hardwiring. Obviously a thermostat is part of the equation and a spur to power it. Is this really a "must" for a qualified electician? It doesnt sound too difficult! Im supposing ignoring it and DIY, would mean a potential insurance problem?



Cheers



I can't answer this I'm afraid. I laid onto concrete.

The kit I used said just put the probe between the wires - and not too close. There was no mention of digging down and I didn't. The probe wasn't must thicker than the wire.

There was some gumpf about not crossing the element with the probe as well, so I didn't.

I put in a completely new circuit for the underfloor heating with it's own MCB on the fusebox (and it has to have an RCD, so I put it on that side of the CU). I believe this would now Part P notifiable (I did it a couple of years ago, although I wouldn't bother notifying if I did it today). It ain't hard, but know what you're doing if you're working on leccy. It would probably only be an insurance problem if you screwed it up and burnt your house down. You're not going to do that are you?

The other advice I would give is make sure you test the heating before you tile over, and then every so often as you tile. You can normally stick a nornal plug on the cables and power it up that way. Oh, I was using "warmup" brand stuff.

Sounds like marley floor tiles, they're usually stuck down to concrete with a bitumen type adhesive, and are relatively easily removed with a heady duty scraper/blade

Assuming that they are, would I really want to dig them up? They do form a good flat finished surface and obviously using heating onto concrete isnt recomended.

However, I am asking in case these tiles are not suitable to lay on - and am accutely aware of the potential for them to melt - and obviously why Ive asked!

You won't melt them, but you will soften the bitumen enough for them to lift. If you lay onto them, the floor will come back up fairly quickly.

A hot air gun is one good way of removing plastic-bitumen floor tiles.

The only other option to removing them is to screw down some ply, then tile onto that.

Oh. Thats not good then! ;-)

Only problem with that option is it raises the floor higher and dont want to do that. I way well remove the tiles, then do that - or use the thermal boards they recommend. I need to look into this a bit further.

Many thanks for your help.

If you can I'd use 6mm aquatherm board - gives you a better surface to work on, plus insulates. I've just fitted some DEVI stuff from cj electrical. Seems good and straightforward - I particularly like the controller/thermostat as it includes an air temperature sensor as well as the floor probe, it learns how quickly the floor heats so that it controls it more efficiently, and multiple thermostats are linkable so that you only have to set the timings on one of them. Also CJ sell the

6mm aquatherm - most places only do 10mm.
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