All right. I had also googled the story with the geotextile in the meantime. That doesn’t seem to be a big deal! Thanks Pinkiponk! Our house will be a bit bigger, and we will also have the base slab constructed by the manufacturer (knowing that you pay a few hundred euros more than if you contract it out externally. But we simply don’t have enough knowledge and confidence to procure such a fundamental component ourselves and coordinate between the companies). However, the MSH is included. As far as I correctly understand, this is standard nowadays with mid-range providers and can no longer be “unordered.” Likewise, our manufacturer will take on part of the earthworks according to the construction service description, namely excavation, construction, and refilling for the frost protection strips down to a depth of 80 cm. How exactly that will work, I can hardly imagine. After all, “80 cm depth” is currently, due to the upcoming backfilling, about 10-20 cm ABOVE our ground level. But surely others will think about that... (I hope...)
Putting the worries aside is incredibly difficult for me. Surely many feel the same way. Currently, we feel more than betrayed by the construction manager of the house manufacturer, with whom we had already made a meticulous calculation weeks ago. Surveyor, building permit, soil report... everything costs at least 1,500 euros more than calculated. For example, the building permit: 500 euros was estimated, we made it clear several times that we do not have that much more money than the total sum calculated, so what happened last week? A look at the fee schedule of the city of Duisburg is enough to find out: the permit will cost 1,500 euros. The surveyor also works according to the fee schedule and wants 5,500 euros instead of the calculated 3,000 euros. We fall off our chairs every day. And now comes the big chunk for land preparation. If there are 50-100% cost overruns here as well (approx. 30,000 euros), we will be bankrupt even before the topping-out ceremony. Nobody expects a precise to-the-cent calculation. But that also means that sometimes you are charged a little more here and there than it ends up being. After all, you do trust the architects, house sellers, and construction managers. What other chance do you have as a building layman, and why shouldn’t you?? I don’t question every other service either that I do not do professionally myself. So far, we have to pay extra everywhere, which completely (really completely!) robs us of the anticipation, pride, and currently sleep.
But back to the topic: the static calculations are also done by the house manufacturer. In principle, he builds the house completely, provided the ground is prepared (by us). We have already signed the contract (to secure the fixed price, but we are still within the cancellation period), the bank follows the day after tomorrow, and in April the notary for the land. So unfortunately, there is no changing the contracts anymore.
Netuser, your answer also helps me a lot. From my point of view, a concrete number, as concrete as it can be estimated. Thanks! You calculate “high,” but I believe it will tend to be expensive for us as well. We are building near a water protection area, so only Z0 natural gravel is allowed, no RCL or something like that. But as I said, if we hit the budget here, the champagne corks will pop. Apparently, our construction manager has contact with an earthworks contractor who supplies, installs, and compacts gravel for 22 euros net per m3. You calculate more than 40 euros per m3. Based on experience, you are probably right!