Unpredictability of construction costs - Will the project fail because of it?

I would change the floor plan again. Where is the garden access? The mini granny flat is actually not meant to be rented out. And is that what you want?

Gather your documents and get advice from a lawyer. Do you have a contract now or not? Is the price allowed to be increased, etc.

And what’s the point of changing the floor plan? The garden access is in the area of the dining table.

And the mini granny flat is never meant to be rented out but is only for the teenage daughter. Since we had to make a basement anyway, we planned this to receive the subsidy.

If you have doubts that the increase is lawful, then you can probably have it checked legally as well. An initial consultation usually doesn’t cost much(?) and maybe there are already some findings.

What you then do with the information gained from that is the next question. If the answer is no, they weren’t allowed to do that, then the question is whether blocking 100% really gets you anywhere. At least it would give you a stronger negotiating position, however you then use it (there is a lot of room between swallowing every increase completely and blocking everything).
And if the answer is yes, yes, they were allowed to do that, it would also be important for you to know if they are allowed to do that in the future as well (and if so, to what extent) and what your options are. So, I have no legal knowledge there, but if my bank changes the conditions for my checking account, I can usually cancel with shorter notice periods, etc. Or object, but that can also have consequences. Something like that.

So for me, it would probably be important first of all to know whether what has happened so far was correct and what could actually still come your way. And only someone who knows construction law and dissects your contract again can really explain that to you. (Just because you get advice doesn’t automatically mean you have to sue or anything)

That's exactly it. We can't get out, but they can do whatever they want, that can't be right?

The following wording was included “ The contract stated that the prices are binding until 03.03., for any later order placement they reserve the right to adjust prices.” However, the order was placed on 14.02. And there was nothing about being non-binding or similar.

What does the contract say? Most contracts state that after the price binding period expires, costs will be increased according to the construction price index

At Zapf. Double garage with two doors.

What is on the plan is not a prefabricated garage.

That's the point. We can't get out, but they can do whatever they want, that can't be right?

The following wording was included “ The contract stated the prices are binding until 03.03., for a later order placement they reserve the right to adjust prices.” However, the order placement was on 14.02. And there was nothing about being without obligation or anything similar.

No, you misunderstand. You signed the offer before the date (03.03.). That means acceptance of the offer is equivalent to a contract. Therefore, the contractor cannot adjust the price. Unless they are threatened by insolvency.

Only if you conducted another negotiation would that speak against an existing contract.

If the contractor wants to change the price, you are off the hook from the contract. Generally, you should still have done little in advance and thus the damage you would have to compensate the contractor for would be rather small.

This is just my opinion. The exact procedure is specified by a lawyer. They know all the details.

I would also like to see if a redesign of the UG and EG makes sense.

With a ceiling height of 2.60 in the basement, the minimum height (2.40m) for living spaces is hardly achievable. I would like to see the layout. Is there a plan of the property with height indications?

And what’s the point of changing the floor plan? The garden access is in the area of the dining table. And the mini granny flat is never intended to be rented out but is only for the teenage daughter. Since we had to build a basement anyway, we just planned it in to get the funding.

Before everything is scrapped, it can be reduced by changing the floor plan.