The costs did not rise linearly at all, and this was also confirmed to us by a civil engineer who works in the residential construction sector and recently built "as big as allowed" himself. Not even the shell construction rises linearly; many other trades do not increase in cost at all or at least not as long as no additional rooms are added. But that should not be the topic. Financing is not an issue. In the worst case, we build 1 year later and have an estimated 30,000 EUR more equity. But even without this measure, it should not be a problem.
It should be in the range of 185-190 sqm plus attic. Others build 185-190 sqm plus basement. But don't be fooled by the numbers, it is visually probably indistinguishable from a 160 sqm house of, for example, 10.20 x 10.20. One side is 14 percent longer, the other side is 3 percent longer. You never see 3 percent, and even 14 percent I doubt.
Its size is roughly comparable to a Weberhaus CityLife 600 or even a bit smaller than a Lifestyle 29 from Massa Haus, which stands among other places in Bannewitz near Dresden (pictures on Google with the respective keywords). The latter house was, as I was told, ordered twice for the mentioned construction area. So our house would not even be the largest in the development.
4-family house? If you subtract usable units, add corridors, etc., maybe 30-40 sqm remain for each of the 4 families on that floor plan.
Do you see any possibilities to make compromises WITHOUT reducing the space offered?
Just for comparison, the house with a hip roof. However, the expansion potential would be very limited here, and we might have to consider a basement.
Edit: Another house for visual comparison: the Helma house Leipzig. The floor area is almost exactly comparable, but the eave height is significantly higher, while the roof pitch is much less steep. These are not unusual dimensions that we have here. It’s just a "somewhat" larger house.