Yes. It exclusively concerns rooms that are located in non-full stories. Thus, a supplement to the "normal" regulation, as stated in my post.
So the rooms in a converted attic, which is not a full storey, would be included in the calculation?
Your project is not that simple.
No idea if you brothers are single, staying, or have families.
But if you build a two-story building where one side, ground floor and upper floor, has one residential unit on, for example, a 9x9 area (a typical semi-detached house) for a family of four and attached to it a two-family house with one residential unit on the ground floor (parents) as well as the upper floor for a couple on an area of 108 sqm, then the floor space index is already reached with 380 (189 x 2, roughly calculated). Of the allowed 270 sqm, 189 are taken, leaving 81 sqm for paths and ancillary facilities. That is not much.
Which project exactly? So far I've only read confusing stuff about living space, residential units, semi-detached house, brother, and pieces of the development plan puzzle. Show us the plot, tell us where we can find the development plan, share your goal, your requirements, and your budget.would the project be realistic then or not?
What kind of project? So far I have only read random stuff about living space, residential units, duplex, brother and zoning plan puzzle pieces. Show the plot, tell us where we can find the zoning plan, share your goal, your requirements and your budget.
That doesn't fit. 380 sqm x 2000€ makes 760,000€ 170 sqm basement = 170,000€ Additional building costs, outdoor facilities, kitchens...The budget for the construction (without land) is max. 750,000€.