I need suggestions on your approach in tiling over Marley tiles (80s). The customer wants U.F.H.

Here is the situation:
There was no mentioning of UFH until I nearly finished prepping the floor with Multibase (main substrate is screed). The floor was nasty, and managed to smooth it out (mostly) with two application of the SLC.

50% of the floor has a SLC thickness varying between 6 - 12mm, with the thinnest section to another 30% of the floor going to a couple of millimetres.
The rest is feathered to nothing, you can see the old Marley tiles.

If I knew in advance, I would have stripped the tiles off, hired a scrabbler and mechanically removed the black glue, then applied the SLC and tiled.

Now, what would you do in my situation?

1) Apply yet another 6mm of SLC?
2) Board off the floor with ..................?
3) Overlay with Ditra matting?

Consider that I usually apply 2 coats of SLC after the cable has been installed.

Over to you people.

I would remove the Marley tiles and then SLC again all over.

Originally Posted by Sir Ramic

I would remove the Marley tiles and then SLC again all over.

Thanks Sir!
Are you suggesting the above on the section where the marley tiles are visible or do you mean ALL of the floor. Kitchen units have now been installed so complete removal is not viable.

The first thing that jumped into my head is I often remove marley tiles with a heat gun and you're talking about putting a heating mat on top of them. I don't know what would happen there.

You should have removed the marleys first mate.

I would install insulation boards.. best to heat just the tiles and not the slab as well..

Originally Posted by SandyFloor

The first thing that jumped into my head is I often remove marley tiles with a heat gun and you're talking about putting a heating mat on top of them. I don't know what would happen there.

my first thought too

Originally Posted by diamondtiling

You should have removed the marleys first mate.

I was not told of any UFH prior to it hence the reason for not removing them.

Originally Posted by Dave

I would install insulation boards.. best to heat just the tiles and not the slab as well..

That's my feeling too mate.

I was told by a local tile shop that I could use Ditra matting but I do not like that idea.

Which type of insulation board would you suggest Dave? It needs the thinnest possible though!

Another thing... I am not sure of what wattage the element it's gona be... I assume that it is for warming the floor only and not as a main source of heating.

IMO 10mm min.. but you can get 6mm if height is an issue.. You have loads of choice really to buy from... Uheat do their's and wedi or warmup etc etc..

Ditra will not insulate a floor..

Originally Posted by Dave

...Ditra will not insulate a floor..

I knew that, that's why I was not convinced on using it.

If the UFH is low wattage I should be fine with the 6 mm, the heat transfer should be minimum. I will be removing a section of Marley tiles up to where the existing levelling compound is to a depth of 6.

would the extra 4mm make any difference franco.. 10mm will help with heat loss that's all mate..

Originally Posted by Dave

would the extra 4mm make any difference franco.. 10mm will help with heat loss that's all mate..

Assuming that the board is 6 mm, the cable is 4 mm thick, the SLC 5 mm (over the cable), the adhesive 6mm, then the thickness of the tile 8 - 10mm.

We are looking at a minimum 29-31 mm, so looking at that, another extra 4 mm can take it to 35 mm visible at the door.

Before anyone comments on the 5mm top levelling... I always do this for cable protection as once had to replace a tile that had a small glaze blemish on it... that made me swet a bit... when I had to Multimaster the old ahesive off and got to see the red cable coming through. So, the 5 mm extra self levelling will be applied. LOL

I will have to discuss it with my contractor first.

I think you will get the adhesive to compress to 3mm..lol

Yeah, sure but you know how it is... always allow for a little more... than less.

Let us know which way you go, perhaps with a few pics hey!!