@ :
There are now many hints regarding the installation after the postings. Also with accurate statements. I summarize them here once with my own comments:
1. PVC planks with factory-applied dry adhesive on the back are to be installed.
2. In the residential property, a flowing screed (probably CAS-based) is available as the installation substrate, in which heating elements have been installed (warm water underfloor heating).
3. Due to unevenness, which cannot be avoided even with flowing screeds, these undesirable structures will show through the top covering without prior smoothing of the screed surface!
4. If the entire surface is not sanded beforehand (as a mandatory cleanliness sanding), the PVC planks, if installed directly on the screed surface, will probably loosen in several places, if not everywhere, at least at the edges. Renovation during the occupancy of the apartment is more than just unpleasant. Especially since the chosen approach of not smoothing contravenes the recognized rules of the trade (exception: solid parquet)!
Conclusion:
What is aiming at is a special construction that will very likely not work. The adhesive strength of the dry adhesive is opposed by an improperly pretreated substrate, but the PVC planks must be able to establish a sufficient bond to the installation level under the thermal load of underfloor heating. And they certainly will not, at least not everywhere! Where the PVC planks lie firmly, the structures of the flowing screed (which arise at least during degassing directly after installation, meaning: during "swabbing") will inevitably show.
If you therefore compare the additional effort (sanding, vacuuming, priming + smoothing) with the risk, which consists of a foreseeable damage together with the effort to fully renovate during the living phase, leaving aside the unsatisfactory surface appearance here once, then the decision regarding the procedure should at least be made in favor of the sanding and smoothing method with this insight gained here.
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Regards: KlaRa