How much additional cost according to the structural engineer's calculation?

Yes, but now the black tank came unexpectedly, which we need according to the soil survey.

best regards

Yes, that’s what I meant: everything concerning your property is of course not included in the house price.
My example with the foundation slab is the basement in your case. Some only buy a property after the survey or wait for the survey before going to the bank for calculation.
I assume there is also a construction service description for the basement and that nothing about waterproofing is mentioned there, so that the amount only arises now?
I thought black tank means waterproofing and is common or has to be done, but it is cheaper than a white one?

If you are building with a basement, then your house costs 400-500,000€? Then a 20-40,000€ buffer should be planned.

And that you are supposed to waive the special termination right in writing, is that normal?

That is probably not normal. But you don’t have to sign.

Yes, that’s what I meant: everything concerning your property is of course not included in the house price. My example with the foundation slab is the basement for you. Some only buy a property after an appraisal or wait for the appraisal before going to the bank for calculation. I assume that there is also a construction specification for the basement and that nothing about waterproofing is mentioned, that this cost is only now coming up? I thought black tank is waterproofing and common / must be done, but is cheaper than a white tank? If you are building with a basement, then your house costs 400-500,000€? Then a 20-40,000€ buffer should be planned. That’s probably not normal. But you don’t have to sign.

Yes, correct – 423,000 euros including tiles, painting and flooring. Apparently the black tank is extra because only drainage is included in the price, which we can’t use now. Best regards

Yes, that’s what I meant: everything that concerns your property is of course not included in the house price. My example with the base slab is the basement for you. Some only buy a property after an appraisal or wait for the appraisal before taking it to the bank for calculation. I assume there is a construction service description for the basement as well and it doesn’t say anything about sealing, so that amount only comes up now? I thought black tank is sealing and common / has to be done, but it’s cheaper than a white one? If you build with a basement, then your house costs 400-500,000€? Then a 20-40,000€ buffer should be planned. That’s probably not normal. But you don’t have to sign.

Since you apparently know your way around, I wanted to ask what the earth removal approximately costs, no one could tell me that either.

What kind of special termination right have you agreed on that you are supposed to waive? Every demand of "sign here that you waive your right XY" would initially make me suspicious as well.

What kind of special termination right have you agreed to that you are supposed to waive? Any demand like "sign here that you waive your right XY" would first make me suspicious.

They said otherwise they cannot start the planning.

Since you seem to know your way around, I wanted to ask how much earth removal roughly costs, no one could tell me that either.

No one can tell you that without context. I only know that removal is currently extremely expensive. We have spread all our earth material around the property because removal is too costly for us. We were given a figure of about €400 per truck trip, and that doesn't even include the landfill, just the transportation. And in the context of cellar excavation, what fits on such a truck is quite manageable. Can you store it somewhere on your property? If not, can you repaint the cellar? I don't think this was planned properly. If no waterproofing was factored in, and you didn't budget for earth removal / earthworks, this could blow your budget.