Basement semi-detached house soundproofing

Hello everyone :)

I have a small problem and hope someone can help me.

Our project is a semi-detached house with 3 units each. The foundation slab is monolithic and the basement is constructed as a white tank. Construction is done with prefabricated elements from the company H+L Baustoffwerke GmbH. So far so good. Our building inspector has now criticized that the gap between the two houses in the basement area was concreted and that this represents a sound bridge. This circumstance was pointed out to our site manager (and H+L). The response from H+L was that they always do it this way and can only guarantee the white tank this way, and if we accept this (with a signature), they will upgrade the upper floors to a higher sound insulation status free of charge.

What do you think? Are they trying to pull a fast one on us?

Here is a picture of it

What you can expect in terms of sound insulation depends on the contractually guaranteed quality agreement in which specific sound insulation values are set for the individual floors/components, etc. For example, based on a detailed component structure with either standardized, proven sound insulation values or your own component structures with sound insulation certification.

In your case, reduced sound insulation values are to be expected for the basement/ground floor, which can be improved again on the upper floor. As mentioned, it depends on what was originally agreed upon.

Thank you for the response, sound insulation according to DIN 4109 was agreed upon, whereby I have read various BGH rulings and understood them to mean that DIN 4109 does not correspond to the current state of the art and the client has a claim to increased sound insulation, regardless of the contract, as explained in [Beiblatt 2 zur DIN 4109].

We have a semi-detached house with a white tank. Nothing needs to be concreted, but two completely separate white tanks were built side by side. There is no connection between them. The white tanks can also be created separately - whether he is tricking you? No idea.