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.

https://imgur.com/MEUxqiz

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

On 07/06/2020 11:49, ss wrote:
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?

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.


Any other thoughts on this.

https://imgur.com/MEUxqiz

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.



--
Cheers,

John.

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On 07/06/2020 11:49, ss wrote:
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.

https://imgur.com/MEUxqiz
If the floor is reasonably level just use a thick cement bed.

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


--
€œIt is not the truth of Marxism that explains the willingness of
intellectuals to believe it, but the power that it confers on
intellectuals, in their attempts to control the world. And since...it is
futile to reason someone out of a thing that he was not reasoned into,
we can conclude that Marxism owes its remarkable power to survive every
criticism to the fact that it is not a truth-directed but a
power-directed system of thought.€�
Sir Roger Scruton

On 07/06/2020 17:02, John Rumm wrote:
Any other thoughts on this.

https://imgur.com/MEUxqiz

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.

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