Floor plan planning shortly before submitting the building application

During the earthworks, they have now discovered that the demolition contractor apparently left old house foundations standing. They also found construction debris, roots, and concrete residues in the excavation pit. Some of it must be disposed of as Z2 and causes significant additional costs. Unfortunately, this could not be seen at the end of the demolition work, as apparently something was dug over it.

It will surely be difficult to prove this.

It will surely be hard to prove that.

Try not to always find a deliberately guilty person! Even with new construction, you are not protected from surprises, which is why, among other things, it is advisable to plan reserves for unforeseen events and not to stretch yourself financially to the last euro.

Try not to always deliberately find someone to blame!

I see it differently. If I hire a demolition company to tear something down and dispose of it, they can't leave half of it standing and bury the waste directly on the site. The guy deserves to be punished for fraud.

I understand that you see it differently ... your selective perception is also interesting ... I do not read anything in the post by the OP that half of the demolition remained on the property, nor in any sentence about buried garbage.

Well, I wouldn't see it that simply here either. I don't know the background, but two scenarios come to mind for me right now:

1. The OP bought the property after the demolition, then I would feel fooled in his place and would call the seller.
2. The OP commissioned the demolition themselves, then I would feel fooled in their place and would immediately call the demolition company.

That the OP is interested in finding someone to blame is probably understandable. That he should set aside financial reserves for unexpected events is another matter, but has nothing to do with the issue at hand, not even if he mentions the additional costs.

I do not read anything in the OP's post that half of the demolition remained on the property...,

... that the demolition contractor apparently left old house foundations standing.

... also not a single sentence about buried garbage.

They also found construction debris, roots, and concrete remnants in the excavation pit.

Can this be misunderstood?