Additional costs (this is off to a good start)

The property already belongs to us and it has also been surveyed.

What I mean is the staking out of the house.

Then it is not a developer.

I have concluded a contract with the company that they will deliver a house from the foundation slab to the washbasin.

It is not about what the correct designation would be.

I am simply surprised that if the company commissions a subcontractor with a service, such as digging the pit for the foundation slab, this subcontractor charges me any costs. Or that I have to pay a surveyor so that this company builds the house straight and to the correct dimensions. I think the company actually has to take care of that itself.

Everything you have bought and still need to pay for is stated in your contract... nothing more and nothing less

But that is exactly what it is about. It does not say that I have to pay for the removal of the excavator. But it also does not say that this is included in the price.

Correct. Everything that is not stated in the contract is also not part of the contract.

And it is indeed about what the correct designation is, because the answer depends on it.

If it were a developer, I would have said: His problem.

But it is not a developer. So everything that is not in the [Bauleistungsbeschreibung] is more or less your problem.