At the time, we built in the same way with my parents and lived well in BaWü for a long time. Our plot was on a slope and about twice as large, so it's not directly comparable. My parents wanted a simple basement flat, which was out of the question for me, so we built them a large, stylish apartment of almost 100sqm including a roof terrace on the upper floor or attic. Today I think I may have overdone it a bit because my parents would have lived just as well in a well-planned 75-80sqm apartment, and as my mother got older, it became too big for her.
The fact that they were on the upper floor (plus a long staircase to the front door) is something I would do again anytime for the following reason: As long as the parents were fit, they could easily walk the stairs to the apartment and it was their training anyway. When it was no longer possible for my father, he could hardly move on his own at all, and we used an automatic stair climber or went down with him 2-3 times a week; after all, we live together in the house. If you can no longer manage that, you also can't move around alone outside anymore, in my own experience, by the way also with my currently 90-year-old mother-in-law. I experience significantly more unsolvable problems on a mental level with older people. My mother then moved again to the grandchildren and also lived there on the upper floor with a small bathroom. She always said that this was better because she could hold on to things everywhere.
What I want to say with that:
I would place the parents’ apartment on the upper floor and look for a nice layout there with a beautiful view and balcony; I would rather avoid a basement in flat country for cost reasons, but regarding the floor area ratio, etc. of the plot I have no idea. I would simply free myself from the sometimes-read urge to necessarily accommodate the parents on the ground floor because their problems and risks lurk everywhere where you cannot prevent them. Falls, etc. usually do not happen at the front stairs but often at small carpet edges, different floor coverings, etc.
Your shown floor plan lacks any furniture, which actually makes your individual life, so as it is, it is not really usable.
Honestly, I don’t like looking at the floor plan because of that, it’s not nice and should be reset to zero. Don’t let yourselves be pressured, it takes time and also conversations.
The children need direct access to the terrace, the parents (that would be the case with me now) are fine with a nice roof terrace or similar.
Maybe you could say more about the background, including that of the parents.
Thank you very much for the detailed answer.
I have partly already written the background in previous answers. Currently, the parents-in-law (both just under 60) live on the third floor in 120sqm. In the future, they no longer want to carry the heavy groceries so far up and would therefore prefer to live on the ground floor. Initially, it was planned that both parties would have direct garden access, but that option was well beyond the budget. They are willing to downsize in terms of living space (but not below 80sqm).
An asymmetrical semi-detached house was also far above our budget, so we decided on the current variant. According to the developer, building upwards is cheaper than building outwards – which also benefits the small plot ;-)
My wife would like the "character" of a house and therefore does not want everything on one level. That was the reason we chose upper floor + attic.
I have already noted your tip about scale-accurate furniture and we will definitely follow up on it.
I am happy to answer any further questions.
