Parquet on underfloor heating without basement - floating with vapor barrier?

Hello,

I am currently facing a little puzzle.
Everywhere I read that for underfloor heating it is generally recommended to fully glue parquet, even for click parquet.
Now, I have chosen laminate with 8mm thickness (0.073 m²K/W) for the upper floor and parquet from Living by Haro from Bauhaus with 11mm thickness and 0.063 m²K/W for the living room on the ground floor. The impact sound insulation for both will be Wineo Soundprotect 0.01 m²K/W, because:

If I can lay laminate floating, why not also the click parquet, which even has a better thermal resistance?
Am I overlooking something crucial?

Under the cement screed on the ground floor is 8cm insulation, below that a bitumen sheet fully applied, then the floor slab.
Do I need a vapor barrier or, put differently, can it harm if I install a vapor barrier?
Vapor barrier also on the upper floor?
There the moisture can escape through the underside. The vapor barrier won’t cause any harm there either, right?

Thanks for your help!

Has been clarified by now.
Please feel free to delete the thread, thanks!

How did you solve it? I have wondered about that myself before.

Was about to write the same: Let the community share in your gain of insight! That is what a forum is all about.

Well, a forum is characterized by people who know something stepping up and answering the question. I now have the information that a vapor barrier at least does no harm. The screed won't wash away, soften, nor will it mold... Whether I really need it, I still don't know, as the site manager didn't want to commit, as with so many things. Whether that's true, I'll see after a few years. Therefore, the information is actually useless to you. Because I myself don't know for sure whether I should believe it.

Yes, well, I hadn’t really thought about damage caused by the vapor barrier either. According to my research when I looked into it, the vapor barrier on the screed is necessary if you assume that residual moisture can still escape and particularly moisture-sensitive floors like laminate and parquet then receive too much moisture and swell. Since there was hardly any residual moisture left after a long drying phase in my case, I omitted it in the upper floor where I laid laminate. That has been about a year now and I cannot detect any damage.

Attention, assumption:
1. The residual moisture must be checked before laying the finished floor anyway; then, if the result is positive, no harmful moisture should escape.
2. If you were to install a vapor barrier and moisture actually wanted to escape, it does so via the edge joints and can cause damage there either to the floor covering or to the skirting boards, unless they are made of plastic. If they are made of plastic, they also act as a vapor retarder (vapor barrier) and completely enclose the moisture under the floor.
Conclusion: from my point of view, this is just a precautionary measure by the flooring manufacturers to protect themselves from overzealous DIYers. Because proving that the residual moisture in the screed was still too high at the time of installation will be difficult. Not installing a vapor barrier is immediately apparent.

It is different with the vapor barrier under the screed. According to my research, that is absolutely necessary.