Are the costs justified?

- the excavation/exchange of soil is now known to always come with the same costs. but one also knows that this can really get expensive. but 9000€ extra for 90cm depth? Bungalow? at 10x10 it should be significantly cheaper.

- plot needs to be filled up? just use the soil from the excavation. that saves multiple times. it doesn’t have to be hauled away, there are no disposal costs, and you don’t have to bring in (or bring in less) soil.

oh yes: welcome to building and the unplanned expenses. if the connection costs already shock you, I wonder how well you actually prepared yourselves.

We are at 120cm soil replacement at ~28k Euros, well, there are a few more cubic meters due to the floor area.

Not every soil is suitable for this, if clay comes into play, then just get rid of it quickly.

that is, to put it mildly, nonsense. you hire professionals for really expensive money. their sole task is to take the blame for mistakes. if I sign off on the accuracy of the work, I might as well level the house myself! you get the surveyor for 600€ for 30 minutes of measuring not so that he does the work, but because his head rolls if he messes it up. the signature is only there to confirm that the work has been completed and an invoice can be issued. the signature NEVER releases the contractor from their duty of care and liability. that’s simply nonsense. the builder is a layperson and can’t verify the accuracy at all. none of these trades will ever get away with that in court.

to the thread opener:

- excavation/replacement of soil is now well known to always be the same with costs. but you also know that it can really cost a lot. but 9,000€ extra for 90cm deep? bungalow? at 10x10 it should be significantly cheaper. the real depth of the excavation can only be seen once you start digging. I consider soil testing nonsense and money wasted. you could have just put the 500-1000€ into the excavation anyway (everyone here sees that differently...)
- does the plot need to be filled? then just use the excavated soil for that. that saves multiple times over. it doesn’t have to be hauled away, there are no disposal costs, and you don’t have to bring in (or bring in less) soil. also consider whether it would make sense not to raise the entire plot by 34cm, but for example go down 1-2 steps from the terrace/entrance platform.
- who is at fault for the planning error with the height no one can tell you like that. you need more information for that
- house connections cost money. that’s no secret and you could have asked about that beforehand. if you plan somewhat properly, Telekom can also throw their cable in there. for us that worked wonderfully. I ordered the water association for Monday, then informed the utility company and Telekom for gas/electricity/fiber for Tuesday that they should please lay the cable Monday or Tuesday. by Tuesday noon the cable was in there. the planner at the water association knows the planner at the utility company (I do too, I trained with him at the utility company ^^) and they coordinated. water association opened the trench, utility company closed it. the shaft at the construction road stayed open 1-2 weeks until all connections were finished. it all works...

oh yes: welcome to building and unexpected expenses. if the connection costs already shock you, I wonder how well you actually prepared.

Then there’s also Telekom. The street will be reopened for this connection and of course we are supposed to pay for that as well. The basic connection costs about 700 euros. The civil engineer who opens the street for Telekom also issues an invoice, but we just can't understand why all this has to be done two or three times and why it cannot be better coordinated.

The surveyor or the architect, we don’t know exactly... also made a mistake measuring. Our house was planned 37 cm too low... so it has to be "set" higher... which means we have to pile up more soil in the garden to maintain the planned level with the terrace. Again, costs that were not planned beforehand. Do we just have to accept that?

That’s why no general advice should be given here along the lines of just backfilling with the excavated soil to save money. If the OP then has to redo the terrace three times in the next 10 years because it keeps settling, they certainly won’t be happy to have saved a few thousand euros beforehand, which they will later have to spend little by little and constantly have a construction site in their garden!