Unauthorized high-quality work - additional costs

What kind of special measures are these? Unfortunately, I have come to know that DIN allows a lot of leeway

Sealing of the earth-contacting perimeter walls according to DIN against non-pressing water.

So basically the minimum.

And what exactly did the soil report say???

Soil report is available, which shows conditions other than non-pressing water.

Because if there is more than non-pressing water, the general contractor really has no other choice?!?

That's exactly how I see it too. Surely one wishes for it to be different communicatively, but would there have been any alternative? Would this alternative have been significantly cheaper?

To me, it sounds like you would have felt better with appropriate communication (rightly so!), but in the end could only nod along anyway.

There are also the so-called Sowieso costs, i.e. one would have had to pay them anyway if it had been known beforehand, as there was no real alternative.

It is a general contractor, not a VOB contract. The soil survey was available before planning.

I have taken out the soil survey, it states:
For structures that cut into the terrain, sealing measures according to DIN 18195 Part 4 (sealing against ground moisture) must be provided.

Basically as described in the construction description. Now higher quality construction was done against pressing water, probably based on on-site measurements or for safety reasons. Exact reasons were not given. I cannot assess the necessity. Information was provided only afterwards. Therefore, there was no approval from me.

Before entering negotiations, I need to know the legal classification. Unexpected additional costs are not regulated in the contract. I am currently of the opinion that the general contractor bears the cost risk in turnkey construction.

Hello Markus, It would be good if you would write that you are either in the planning, execution, or already after moving in as a status. In your last question, it reads as if you have already moved in. And it also became clear that it is _not_ a developer. That's my recollection [emoji6]

Regarding the question: You seem to be hung up on the word “turnkey” and have consciously chosen this option with a general contractor so that everything runs smoothly. However, turnkey can mean anything. It is often used to suggest to builders that they have nothing more to do or that the price remains fixed. The latter is called a fixed price. Nevertheless, during some months of construction, one thing or another can happen, and the ground can also contain quite a bit that could not be calculated beforehand. For this reason, the general contractor has a contract according to VOB or the Construction Code, which should be understood before signing it. There are formulations that inform the builder that the arising additional costs must be borne by the builder. The builder therefore secures themselves well with an expert as well as a financial buffer that can cover unforeseen costs. Turnkey does not mean that you will not face any further costs or work on or in the house. The expert will also check this contract for further costs if necessary so that the financing calculation is complete.

However, a builder can expect that any change or extension will be communicated to them in advance. We ourselves also had to pay an amount of about +-3500 after the soil survey. This was communicated to us by phone, and by e-mail we received a document/offer which we _had to_ commission; without this, they would not have started. We as builders often have to trust the general contractors or specialist companies, i.e., the professionals. We ourselves do not have the expertise to decide.

The general contractor should also be chosen with regard to trust.