Who has experience with Bonum Haus GmbH?

That is why I pointed out that one should go along with it if one wants to have certainty about the basement

That's why I pointed out that you should go along with it if you want certainty about the basement

And that's why I also added that you should take a stone sample if you want certainty about the walls. And if you need even more assurance, you also take frame and glass samples from the windows, etc. I want to say that this doesn't require s... in single-family house construction. A waterproof basement is much more than the composition of the concrete.

It is optional, we simply did not do it

And how exactly does it now manifest that you regret having done this?

In such quality matters, I also see the site manager or Bonum as being responsible. In the end, it should be in everyone's interest that it fits at the end or even after 10 years.

In quality issues like these, I also see the construction manager or Bonum as being responsible. In the end, it should be in everyone's interest that things fit properly both at the end and even after 10 years

Specifically regarding Bonum, I am not sure whether their self-image is more that of a construction director or a craftsman mediator. In general, you can only direct such expectations to an architect construction manager or you must explicitly mention them to a construction-accompanying expert in the contract wording. With a contractor "construction manager," you are doubly at the wrong address – the second time simply because these guys have a care ratio like a caseworker at the job center. Naturally, this is a world of difference from "chief physician treatment in a private room."

Short update

We now have several offers for house construction on the table. All of them include construction management. During the sales talks, two of them also mentioned that the construction manager has insurance. I was also always told that the construction manager controls the quality and, in the worst case, is liable for it.

Here in the forum, however, it rather sounds as if the construction management only takes care of coordination and wants a quick completion of the construction.