Massive problems with the builder - is contract termination possible?

Because of the basement, it actually annoys me the most. After the report was created, we were offered the ground investigation for the WU basement for an additional €13,000. Then we were offered an alternative with a WU slab (necessary according to the ground investigation) but a masonry basement. The whole thing was then only about €9,000 cheaper. That’s why we asked why it would be so expensive, wanted a breakdown of how much steel is in it, how the price of the eliminated foundation was offset, etc.
I mean, if you take a broken car to the workshop, you also get a detailed price for the repair and not just “transmission repaired €3,000”!
In any case, the basement has now been offered to us again as a WU basement, just €2,000 more expensive. And the breakdown is still missing.
We waited another 3 weeks for this. Now the builder wants to start and we should finally decide, otherwise other customers would get ahead, the order books are full and the start of construction would be delayed by months.
Actually, I do have the right to transparency regarding the basement costs. Besides, we have been waiting for him for weeks.

Hi
don’t wait, but take action. What is obvious to the provider is incomprehensible to the customer as a layperson. To resolve this, direct communication is required. The additional cost of 2000 EUR in the last offer can, for example, be justified by a thicker layer of gravel under the basement or something similar. Indeed, this should be presented in more detail in the offer, but you can always ask. And insist on an answer, especially so close to the start of construction. Actually, all necessary things like reinforcement etc. should already be ordered and on their way if it is supposed to start in a week.

Just asking directly: Do you have a flat-rate contract and a [Bauzeitenplan]?

We do not have a construction schedule. Deadlines were not specified, only approximately, at least they were not confirmed in writing. Not even after repeated inquiries. Flat-rate contract? We have basically commissioned a turnkey house.

A question:

Is it possible to get out of the KFW70 in order to use a 30 cm brick? The developer refuses to use a 30 cm Poroton with internal insulation. The reason would be that the walls are already prefabricated and this would not be possible.

We have not yet signed a construction contract, nor an equipment protocol. Construction is supposed to start this week, at least with the surveying. However, the KFW70 application has already been calculated and submitted (which also cost extra). The loan has not yet been disbursed (I believe this only happens upon submission of invoices).

You haven't signed anything yet? Then there are still all possibilities to avoid ruining yourself through the construction... First: The lump-sum contract is absolutely not an option. Otherwise, you are always exposed to some crazy additional claims. And second, a construction schedule must be part of the contract. Third: make sure that the contractor does not have the possibility to demand the entire payment for work against a bank guarantee all at once and at the beginning. That would severely worsen your position during the construction project and you would also have to start paying interest immediately. By the way, according to my calculations, the living area would shrink by exactly 4.68 m² with a masonry reinforcement of 6.5 cm. And furthermore, even after the building permit has been granted, an enlargement of the building by 13 cm is possible without any problems ([Tektur]). Conclusion: Right from the start, there is a game of poker – and experience shows that this will intensify during the course of the construction project.

If you change the wall thicknesses afterwards, the entire structural engineering must be redesigned. Energy calculations must be redone, etc. And then you want to start next week? What exactly is supposed to be surveyed? Sorry, but I would stop the construction here for now. Create clear conditions - establish written agreements for everything and only then start. Once they have laid the first stones, you can’t do anything anymore. It’s very naive to just want to start when fundamental issues are still unresolved.