Property development - basement yes or no?

Yes, I understood that (I thought so ;) ). But then why is the idea of planning 170 sqm being dropped?
Maybe I expressed myself awkwardly in my initial post. When I referred to the square meter figures in the floor plans, I always meant the living area – i.e., spread over the two full floors.
If I stick with the example from post #3, in a house with exterior dimensions of 12 x 9.5 meters, I have a built-up area of 114 sqm.
I calculated: 477 * 0.3 = 143.1 sqm, plus 50% of that for ancillary areas would be about 71 sqm.
In this example, I would therefore still have 143.1 sqm – 114 sqm + 71 sqm = 100 sqm "left over" for ancillary areas.
Is it unrealistic to get by with that?

If it matters: Our development plan dates from 1989 – therefore the 1986 Building Use Ordinance should apply to us.

Sorry, I can no longer update the initial post. So here are the plans again, each with north marked. I hope it is understandable. I rotated the development plan so that the orientation matches in all plans.

ok, I had read that as the base area.

Hang Minimal

Do you have a specific number for that? Like 0.3m height difference in the building window? Estimating a slope by eye is rubbish, but the economic efficiency and practicality of a basement is decisively determined by how much slope there is. The other points are energy standard and plot size. Currently, I would assess it as follows: Slope: probably against Energy standard: ? Plot size, floor area ratio: in favor When it comes to storage space, often you can achieve a lot simply with a large attic.

You mean the plot size and floor area ratio suggest a basement? So far, we unfortunately do not have a concrete figure regarding the slope. Who determines that? Is that the surveyor’s responsibility? Regarding the energy standard, we have so far tended towards KfW 40 EE, as the majority of the conditions are already met through our desired building technology. However, if, for example, a basement would only be affordable with KfW 55, we would have no problem with that either. The soil survey will be conducted the week after next.

You mean the plot size and floor area ratio suggest a basement?

Yes, the less area you are allowed to build on, the more valuable it becomes to move things like a technical room and storage options underground. Specific information about the slope can be found, for example, in the cadastre, where the contour lines should be marked. Otherwise, you can buy a hose level for little money at the hardware store and measure it yourself. I am a burned child in this regard; our "very slight slope" is 2m across the plot with 70-80cm in the building window. But I must also say, now that the foundation slab is in, it doesn't seem that much to me.

Because you write above "otherwise 2 parking spaces in a row," have you even clarified whether tandem parking spaces are accepted?