Plot Single-family house C630 Heinz von Heiden at the location Saxony

Is that written like that in the contract? It doesn't make sense to me.

Yes, that's true, I need to correct myself. We have a different construction service description due to the self-performance. The original version from the initial consultation includes excavation of 30cm and compacted gravel including 1m all around. Although I find that strange because Heinz von Heiden assumes 2m all around. Also, in hindsight, I really find the €2500 credit way too little. I also asked the civil engineering company that works for Heinz von Heiden, and they want over €1000 just for the construction site setup and around €12.5k in total without gravel!! Well, there is also some crane area and parking spaces included, but with their offer, I end up at over €15.5k with gravel. And we only have to excavate/heap up 20-30cm more.

That's what I thought. Exactly reading the contractual content that is omitted.

Makes sense. The profit stays with the company, and part of the costs is reimbursed to the client ;)

And when the additional costs come, you have to pay an extra 12-13k. Nevertheless, it is cheaper if you do it yourself. This way you save 4-5k€. I did some calculations. At 30cm, you have about 40m³ of excavation and 70t of gravel. Gravel alone would cost 1,250€. That would be 1,250€ for setting up the construction site, storing materials on the side, and placing/compacting/preparing the base.

The original question whether it is based on hours or quantity is more because I wanted to know if anyone had something comparable. It would be interesting to know how long a civil engineer usually takes on average for excavation/foundation.

He can more easily cheat on hours, although the time indication is already quite generous. I believe our civil engineer back then took three days for the excavation and the fine grading. I could be wrong, maybe it was a week. But it was 1m excavation and 1.2m fill (about 120m² base area).

For quantities, you get weighing slips and thus have proof.

I would also advocate for the neighbor.