Hold the architect liable for faulty planning?

Hm, I also think that one should have a) seen it on the plans, b) noticed it on the construction/site. I still remember that we often had our ear to the street to check the level at 10cm. With that I want to say: as a builder, you are actually very anxious and sensitive about whether you are at the right height or if the distance to the neighbor is correct. Just anonymously post the cuts to see if a layperson can recognize it.

First of all, thanks Bauexperte for the detailed answer.
We did not insist on the pitched roof. We had it as an idea and the architect implemented it. We also had another house for comparison, but architecturally it did not appeal to us as much as the current one. In terms of the slope, however, it would have been the better (and financially in any case more) reasonable solution based on the current situation.
I think it can be designed nicely, but the question is whether there will still be enough budget at the end to have it done professionally.
Regarding the drainage issue: We are building with a white tank and drainage and also in rock, plus the sloping street location. Since the basement is level at the bottom, fortunately that is not a problem, everything drains nicely.
To clarify again, we were aware that we would have a lot of earthworks. We were also aware that the garden behind the house is not level but slopes over the entire area. But we assumed that the slope would continue its normal course and that we would not build so much in that area that it would first need to be excavated.
I read somewhere about a court ruling where a builder won a legal dispute because of poor advice from the architect. That’s why I thought I’d ask here if anyone has experience with that.
Over the weekend I had a friendly appraiser come to the construction site and someone who knows about landscaping... let’s see what they say...
I can gladly upload the floor plan sometime, next week at the office ..

Good evening,

First of all, thanks Bauexperte for the detailed answer.

You're welcome

I read somewhere that a client won a legal dispute due to poor advice from the architect. So I thought I’d ask here if anyone has experience with this.

I remember having read about that.

The "problem" will be proving that your architect is responsible for the additional foundation costs, which would not have occurred with more careful advice – as you describe it.

Over the weekend, I called a friend who is an expert witness to the construction site and someone who knows about landscaping… let’s see what they say…

I would be glad if you kept us updated; it certainly won’t make us any dumber

Rhenish greetings