Possible residential floor area

I once marked your property in a picture from a presentation found online - to illustrate how the developers of the building area envision its development:

We intend to build a basemented semi-detached house with 3 residential units (a normal semi-detached house with approx. 140-150sqm and a semi-detached house with two apartments and a total of approx. 230sqm).

There you go, it works. At least a start has been made.

I have marked your plot in a picture from a presentation found online

Close only counts in horseshoes. [ATTACH alt="Bebauungsentwurf.png" type="full"]52956[/ATTACH] But never mind. The visualization shows very well how many freedoms the development plan allows. Only the floor area ratio is too small for the OP's project, although he leaves open how the specific numbers regarding the desired living space were arrived at. Maximum floor area 773m² * 0.5 = 386.5m² corresponds roughly to 80% * 386.5m² = 309.2m² living area. Now you might be able to squeeze out a few more square meters with non-habitable rooms in the non-full storey and wall thicknesses, but IMHO it should be over at 330m². Since more precise information on the intended legal division (co-ownership, ideal division according to WEG, real division), the space requirements and the design wishes (villa instead, Bauhaus fake, retro style, etc.) are still missing, I recommend, contrary to my usual efforts for maximum independence, a multi-family house with common traffic areas (hallway and stairwell), shared building services and WEG division in view of the tight space and limited budget.

Since more precise information about the intended legal division (co-ownership, ideal division according to WEG, real division), the space requirements, and the design wishes (substitute villa, Bauhaus fake, retro style, etc.) is still missing, I recommend, contrary to my usual striving for maximum independence, considering the limited space and budget a multi-family house with shared traffic areas (hallway and stairwell), shared building services, and WEG division.

But even there, one could create the desired solution of the quasi two-unit building with one side maisonette (with an external main entrance like in a semi-detached house) and the other side a two-family house – and with a kind of "house-garage-hatch door" one then changes into the main stairwell when you want to enter the heating room, and internally within the maisonette one makes do with the usual spiral staircase ...