New building with basement | WU concrete plus ring drainage

Well, I myself work in a construction company, but in multi-storey residential building. Here, WU components like underground garages are now standard, but the discussion is the same every time.

The contractor can only factor in what is tendered.
At first, he cannot know what is desired and of what is desired, the type of execution is decisive. Then the contractor also cannot know according to which concept it is created (allowing cracks and sealing them, avoiding cracks, etc.).. So he can't really say much at first (actually).
The problem is, however, that companies offer "WU basements" or "basements made of WU concrete" despite the lack of specifications, because the term is not protected..
Long story ;)

: What would be the safest possible clause in the offer text for that?

Of course, ideally you have a detailed plan/specifications describing and specifying all WU components precisely, but aside from that, assuming you want to buy a prefabricated basement as a client, how can you protect yourself?

First of all, back to your soil expert -
The water pressing from the outside has no influence on condensation inside. If you want to use the cellar in a higher quality way, insulation should be considered. WU keeps water out from the outside; if the component cools down, water from the air inside can of course condense. This connection is not logical to me.

Of course, particular attention must be paid to tightness - this should always be the case! Usually, a WU cellar in house construction is only tight because the water exposure is low. If the water seeps in so slowly, particular thought should be given to the wall-ceiling connection. Windows or light wells both exist as waterproof against pressurized water - planned high enough so that water does not run in there above ground level…
A soil expert is simply not a WU specialist… a good WU construction does not need anything else for support…

Certainly, the transition from ground floor to cellar must be considered, but it is also feasible with appropriate planning.

So if you have a basement built, the "seller" should at least ask what you want to use the basement for and then inform you about the possible construction methods and the resulting conditions so that the client can make a decision.

Questions should be:
How will the basement be used? Will walls and floors be covered?
Which usage class?
Which design principle?
What wall thicknesses and how are they made?
Which joint sealing system?
How are future cracks dealt with? Who repairs them?
How is the basement connected to the rising masonry?

A specification should definitely include a note on the usage class (there are A and B) and design principle (a, b, or c). If the company cannot explain these two questions, do not choose them.
Additionally, it should contain a note on joint sealing (sheet metal or tape).
One should also write something about how (always expected) cracks outside the joint sheets are dealt with.

And I would advise against taking a basement with element walls, i.e. semi-finished walls that are then filled with concrete. This can have costly consequences in case of a crack.

I can't answer your question quite so easily :D