Tiling to concrete floor

[ss]

Not mine, sons in Holland. He states there is no membrane between the old adhesive and the concrete floor (with underfloor heating), so what to do.

I am thinking if he cant take the old layer off then to level first to even out the old adhesive grooves and then fresh adhesive for tiling. Questions: Is this the way to go, and Will the fresh adhesive stick to the old adhesive?

Any other thoughts on this.

[Tricky Dicky]

I would give it a covering of self-levelling compound. It will be a bit expensive using tile adhesive as both adhesive and filler not to mention how the extra thickness might might affect setting times and ultimate strength

The better quality self-levelling compounds do tend to stick like sh*t to a shovel to most substrates as long as they are sound. There is a type that rather than mixing with water it is mixed with liquid latex which I have been told is more flexible which might be a good idea with UFH. I used some a long while back and unfortunately cannot remember the brand but a good tile supplier/builders merchant should be able to help you out.

Richard

[John Rumm]

It will - although if doing it just with adhesive you would need to do a full bed of it, with ribs on top rather than just ribs.

Latex self levelling compound - pour on, trowel roughly into position and leave it alone - it will consolidate the surface into a flat smooth one, ready for new adhesive. Judging by the size of room, he will only need one 25kg bag.

[The Natural Philosopher]

Only use compound to fill in really low spots - frankly its almost as expensive as tile cement

I put levelled strings in my kitchen before tiling as guides and used tile cement all over up to 2" deep in one spot, and less than 1/4" at the high spot

Works fine with UFH

[ss]

Richard & John Rumm. I have passed on the info, thanks.