Building in existing structures - Subsequent additional costs despite a fixed price

The question is whether it is really beneficial to enter into a legal dispute with the construction company before the execution? If he does not get the money from you now, he will charge additional costs for every nail within the maximum tolerance range. If the costs are significant and make the construction nearly impossible, the goal could rather be a termination of the contract by mutual agreement.

What are your arguments/reasons that with such a wording the problem can be shifted onto me, or is that just a feeling? This is not meant to be rude at all, but I'm really looking for some reliable clues so that I know how harshly I should discuss the matter with the GÜ...

In my job, part of my task is to find loopholes, definition errors / inaccuracies, etc., or to prevent these from being disadvantageously incorporated into contracts for my company. The excerpts you post from the contract are all not particularly good. Example: point 17: exterior wall thermal insulation. If there is not yet a proper definition of the insulation material including manufacturer, etc., he could also use sheep dung. Five specialist lawyers will produce six interpretations of your contract documents for you, the seventh may then be a judge. I agree with : If you want out of the contract, then let it come to a legal dispute. If you want a house, come to an amicable agreement.

If he doesn't get the money from you now, he will charge additional costs for every nail within the maximum tolerance range

Not only that. It is also quite possible that work will simply not continue until the matter is resolved. There are plenty of excuses to be found.

I am currently building a single-family house on an existing basement. At the beginning of April 22 I signed the offer at a fixed price. Five months after the contract was signed, I was informed that the existing foundation cannot bear the load of the new house and therefore needs to be reinforced. I am supposed to bear the additional costs in full.

The contractor, if you ask me, does not want to put his people on short-time work during the declining construction market and has to maintain order volume. In my post #9 of your old thread (the basement shown there, from my point of view, is not suspicious or too weak) I linked you a comparable case, which you also apparently followed up on to my recollection. Of course, it may be that the new building has load-bearing walls located unfavorably from a load transfer point of view – however, I do not recall knowing your new construction project.

Nobody is talking about a legal dispute. It's about finding an amicable agreement. We are talking about costs just under 20k. That is nothing that endangers the construction project, but still an unplanned, unfunded expense that we would have preferred to have absorbed elsewhere in the house.

In September 2022, I received an email that said: "The structural engineer commented on the foundation under the middle wall, with the conclusion that the extremely eccentric strip foundation leads to an impermissible edge pressure, which exceeds the allowable soil pressure by 190%."

My point was that it would be cheaper to rebuild the wall rather than underpin the foundation.

This proposal was rejected with the reasoning that even with a concentric wall, the foundation is not properly dimensioned.

Again, my concern: I do not want a legal dispute, but a fair solution, e.g. 50:50.

Do I have more than "motalische" arguments on my side here, or are you generally of the opinion that I am out of luck?

What do you mean by "the contractor has to [...] increase order volume."?

I find all of this very unprofessional or deliberately non-transparent communication. We were always led to understand that we could carry out the construction project this way; otherwise, we would not have signed...

I don't want a legal dispute, but a fair solution, e.g. 50:50.

You will only get that if your contractor understands that he cannot push 100% of the costs onto you. And for that, you need a professional on your side.