Rough construction flat-rate offer - forgotten necessary items

Hello everyone,

we had a flat-rate offer made by a shell construction company based on our floor plan. Unfortunately, various insulation baskets were forgotten here, without which the construction would have defects (numerous thermal bridges).

These are now being charged to us for several thousand euros after the contract was signed. Is this permissible? Without these insulation baskets as thermal insulation, the construction could not be free of defects, right?

Thank you very much for the responses!

we had a flat-rate offer created by a shell construction company based on our floor plan. Unfortunately, various insulation baskets were forgotten,

I do not read an offer "based on a floor plan" as meaning that you also provided a description of the construction services. If no insulation baskets are indicated in your floor plan (which would only be usual in execution plans), then they were not "forgotten" either.

Those who request offers "imprecisely" "risk" price-optimized responses. That is why a "proper" tender is also done by a professional.

Well, that clearly depends on what is written in the written contract. If you don't want to post the contract in a shortened form, you'll definitely have to go to a lawyer - or pay. And even if you post the contract, they can only give you opinions, not information.

Otherwise, you are basically right. If he sold you an item x, he also has to deliver x. If he forgot something in his calculation - which is absolutely necessary - that is basically his problem at first. The question is whether the iso baskets are really absolutely necessary for the freedom from defects. Without a contract, that is impossible to answer.

question is whether the iso-körbe are really absolutely necessary for the defect-free condition.

For a basic approval of the construction or a professional execution, no: "Isokorb" is a product name by Schöck - in a plan or a contract, one can specify this particular product, but not in a legal standard. So, objectively, a shell construction without "Isokörbe" is not impossible.

so it's a "maybe" thing, because it can also be solved differently? was it agreed anywhere that these baskets are to be used? in writing/orally or something similar? otherwise you might be off the hook. and another way to ask: have all the works been carried out by them and accepted as free of defects? and what amount is it actually about.

There it is again, what has always pissed me off about construction. In my eyes, this is systematic cheating of the builders. It’s not this extreme in any other industry.

Here an offer was made and a decision was made based on the price, now suddenly it no longer fits and the builder is supposed to pay. Since these insulation baskets are necessary according to the shell builder, he should have included them in his calculation. If I were you, I wouldn’t pay anything. How it looks in court should be decided by experts.

But just imagine you ask what a 90,000 km service on a car costs and when paying you have to pay extra for all the oil and air filters. You would never see that dealership again.