I can only keep repeating: Please stop it! Either you buy a system, or you rely on proven installation methods. What has been discussed here for weeks does not comply with the technical rules!! What happens, or put differently: what has already happened in the past with such an installation technique? Well, the so-called "impact sound insulation foil" is nonsensical simply because the actually effective and prescribed impact sound insulation in residential construction is located beneath the screed. And it is at least 20mm thick, so it can absorb vibrations through its material cross-section. A 2 or 3mm thin foil can never provide effective impact sound insulation that deserves that name! Just by looking at the test standard for such impact sound insulating layers, we see that the setup involves a concrete subfloor, then the insulation layer, and on top of this a screed is applied, on which the standard hammer device is placed and activated for sound measurements. A thin foil is never installed under a screed. And since thin-layer coverings on a foil cannot be tested according to standards for the effectiveness of sound reduction, skepticism towards the values stated by manufacturers is also warranted. Now, let’s look at the installation substrate, and this gets even more interesting! Usually, this will be a smoothed screed surface. The result would be even worse if one were to forgo the leveling compound. Why? Every mineral surface has a certain roughness, which creates resistance against horizontal shifts. The rougher the surface, the less a layer slides—logically. Now, if you lay a foil with supposed impact sound reduction on a screed or a leveling compound and connect/fix the floor elements to the foil, all types of coverings are subject to physical laws. For example, coverings expand with heat and contract with cold. Wood-based materials also react to changes in humidity. The covering surface thus "works," it moves. Beneath the covering surface, chaos threatens with the setup "recommended" here. Because the foil is held in place by friction forces against the substrate, the top covering moves alone, the dry adhesive cannot absorb the shear forces, and so the foil starts to roll up under the covering. Initially as small “sausages,” which increase in size over time (due to constant movement of the top covering). This can be seen in the surface of the covering, and from professional experience I can assure you: the expected bumpy landscape looks really bad! The only way to get this "under control" again is full removal of the covering. Including removal of furniture. And at the back, a kind of "smear" of dry adhesive with the foil hangs on the floor elements. Meaning: the floor elements are no longer installable, they must be completely removed and disposed of. ------------------- The question now is: do we rely on our gut feeling that it will just work that way, or do we trust the considerations of a practitioner who (unfortunately) is never called to beautiful and perfect floors, but only when things have "gone wrong"? Regards: KlaRa