Two-family house, optimize?

not related to the development plan at all.

We don't even know it yet!
Maybe the OP is not even allowed to implement his wishes. The development plan I inserted is only for the OP's explanation.

But the possibilities of the development plan are also not that important...

in number 12 the OP inserted one. I can’t get the house compliant or I’m just that clueless or a cold is fogging my gray cells.

in number 12 the OP inserted one.

I overlooked that. But then it already gets really tight with the floor area ratio. But as I said, a) an architect needs to be involved and b) the budget needs a significant increase.

In principle, I have to agree with you, I would indeed like to accept the help of a professional, but if I have to invest several thousand euros in the basic idea, it somewhat discourages me. The home construction company has estimated around 9,000 euros for the architect, so we wanted to do as much preliminary work as possible. Regarding the topic of the granny flat with the young man, an MV will be made so that I also have a little security and, if he moves out after all, I can still rent it out.

What this granny flat costs you more (not just money! especially in quality, as you deprive yourself of some possibilities for your own floor plan in terms of planning!) you can also give to your boy as a rent subsidy for external housing... Let the arguments sink in first, think about it for a few days, and then make your decision again, whether with or without a granny flat.

What this granny flat costs you more (not just money! especially in terms of quality, as you deprive yourself of some planning options for your own floor plan!), you can also give to your boy as a rent subsidy for living externally...
Let the arguments sink in first, think about it for a few days, and then make your decision again, whether with or without the granny flat.

Thats it !