Bathroom underfloor electric mat for tile heating

[Deleted User]

I've just had a quote for a bathroom rip out and installation and it includes electric underfloor heating. The purpose is not to heat the entire room (we have a radiator for this), however to heat the tiles so they are warm underfoot. It sounds nice, although a luxury. The subfloor is just a concrete slab, so I assume a layer of insulation will be required under the electric mat to ensure only the tiles are being heated.

Has anyone else had this installed in their bathroom?

ComicGeek

Is it a concrete slab, or is it concrete screed over insulation? Is it a ground floor bathroom, or above any other heated space? How warm does the floor feel at the moment?

Normally it's just a 6/10mm insulation board that sits below the heating mat, helping to direct the heat upwords - but if it's an uninsulated concrete slab then you definitely want proper insulation below the mat. It does mean that once you've installed the insulation, mat, then latex screed over the top and tiles the overall build-up can be chunky - need to think about how this affects the door threshold into the room.

I installed it in our bathroom 2 years ago. I ran it for about 3 months and it was a lovely luxury in the mornings - after the summer, and elec prices went up, I just turned it off and haven't used it since. 

We have Karndean in the bathroom though, which isn't too cold on the feet - tiles without underfloor heating can be really cold.

fenwick458

use insulated tile backer boards, minimum 6mm, more if you can raise the floor slightly, depends on the threshold at the door?

the warm up time will be halved even with 6mm insulation (and the time taken to go stone cold again when you turn it off will be doubled)

[Deleted User]

ComicGeek said:

Is it a concrete slab, or is it concrete screed over insulation? Is it a ground floor bathroom, or above any other heated space? How warm does the floor feel at the moment?

Normally it's just a 6/10mm insulation board that sits below the heating mat, helping to direct the heat upwords - but if it's an uninsulated concrete slab then you definitely want proper insulation below the mat. It does mean that once you've installed the insulation, mat, then latex screed over the top and tiles the overall build-up can be chunky - need to think about how this affects the door threshold into the room.

I installed it in our bathroom 2 years ago. I ran it for about 3 months and it was a lovely luxury in the mornings - after the summer, and elec prices went up, I just turned it off and haven't used it since. 

We have Karndean in the bathroom though, which isn't too cold on the feet - tiles without underfloor heating can be really cold.

It is just concrete slab on the ground floor. There is no insulation under the concrete, just earth. It's a farmhouse built in the 50s. Considering we don't want to raise the floor height too much perhaps we will give it a miss.

fenwick458 said:

use insulated tile backer boards, minimum 6mm, more if you can raise the floor slightly, depends on the threshold at the door?

the warm up time will be halved even with 6mm insulation (and the time taken to go stone cold again when you turn it off will be doubled)

I'll ask the installer about these. 6mm is not much height to add to the floor.