Received an offer from a builder: Cost of shell construction - experiences?

Can someone just quickly give a rough estimate of how much the surcharge would be from 30cm to 36cm aerated concrete? Possibly this could be used as a negotiation point... (As an upgrade at the same price)

So our contract with the shell builder is at least 10 pages... Everything is listed there, starting from the exact brick, to the exact roof tile, to information on the quantity of steel and concrete... (And for example also the windows and cellar shafts, the roller shutter boxes, etc...) As I said, and that only for the shell construction! Your offer seems very brief to me. However, if you have really only heard good things about the construction company so far, that at least speaks for them. But I would have a few things detailed more precisely. (Exactly which bricks, which roof tiles, how the execution of the foundation slab is, how much insulation goes into the floor and for example into the roof...)

So our contract with the shell builder is at least 10 pages... Everything is listed there, starting from the exact brick, to the exact roof tile, to details on the quantity of steel and concrete... (And for example also the windows and basement shafts, the roller shutter boxes, etc...)

Hello WildThing, could you email this description, anonymized of course. Thank you

So, I'm checking in again. On Friday, we signed for the shell construction. We were still able to negotiate a few things and specify a few things more precisely. I will then upload the plans in the corresponding section.

Many thanks at this point for your opinions and comments

Hello Diddy, sorry I only just read it now... But you have already signed. That means for you it's a fixed price no matter how much steel or concrete he needs? Just like the drainage around the house is included, no matter if and how much pipe is needed?

Yes, that was the statement from the contractor. Quote: If required by the soil survey, we'll just put in a ton more steel... Drainage should be limited based on the experience with the neighbors. The connections are located centrally to the north at the street. 3-4 meters away from the house.