About to throw the trowel in....

[jimbob]

Hi all,

My wife has bought some 450 x 450mm porcelain floor tile (9mm thick) which she wants me to put down in our hallway. As if it could not get any worse, she wants me to put down warmup underfloor heating first. The floor is concrete, I shall be putting down insulation boards first and then the heating wires, then tiling straight on top of those.

I have read a lot about thin-bed and thick-bed, but still can not figure out which is best for me, and what trowel will do the job properly. The heating manufacturers recommend a plastic trowel so as not to damage the wires, but they seem to be few and far between. I read somewhere on here that a trowel with round notches 20mm wide and 10mm deep is correct for flooring. I have also read a recommendation for Karl Dahm Special Maxi trowel, but they are only 12mm by 12mm notches. Will that be enough? Does the adhesive need to cover the heating wire completely? Will it cause a problem if not all the wire is fully covered and some of it is touching the bottom of the tile?

Any help would be greatly appreciated.

Believe me, if I could afford it, I would get a pro in, but with a high maintenance wife.......

Cheers
Jimbob

 

[diamondtiling]

You could cover the heating mat with a flexible self leveller if you want, or you could use tile adhesive, a 12mm trowel will be fine, the wires are pretty tough and i have not damaged one yet, just be careful, follow the wires with the trowel, you should aim to get 100% coverage on the back of your tile ,

 

[Matt]

I generally recommend using Flexi Self Leveller instead of going straight down with flexi adhesive. There is nothing wrong with going straight onto the wires with flexi adhesive, but if you're not careful, you can damage the wire. It can also work out cheaper using flexi self leveller

If the wires aren't 100% covered you risk getting hotspots. So getting a 100% coverage is recommened.

 

[jimbob]

Cheers guys. Altogether now, what is a hotspot not........

 

[Rob Z]

Jim,

We've done a lot of heated floors, and only on one of them do I recall trying to set the tile directly over the wire in one step. I thought it was a hassle and not worth the aggravation. I would definately use a SLC over the mat , and then set the tile in a separate step.

 

[CJ]

Cheers guys. Altogether now, what is a hotspot not........

Showing ya age Jimbob :smilewinkgrin:

 

[david campbell]

defo go with the self leveller,and get yourself a cheap multimeter to test as you go so you don't accidently nick the wire,wouldn't fancy having to lift it all and re-do it:yikes:

 

[White Room]

Again self leveler but make sure any wires are taped/fixed down or the leveler may push the wires up

 

[smurf21]

Me Too self leveller over the ufh first

 

[doug boardley]

self leveller for me too jimbo. A hot spot is a void in your adhesive that expands when heated, and pops your tiles cos its not expanding the same as your adhesive