If you were to follow the idea that led to this very poor floor plan: There should be the option to separate into two residential units.
You, those of you participating here and following the forum, have certainly understood that well. I have been involved with house construction for over 25 years, and with apartment construction even longer. Let's call it affinity. I have been in this forum for 12 years, and you are certainly not the first to imagine a house that unites life today with the family and later, after remodeling and separation, “living on one level.” So something simple, pragmatic, which covers eventualities. In your case, it should even provide insurance. In real life, my job has taken me to dozens of houses and apartments. There is the standard single-family home, then the typical two-family houses, which probably had their heyday in the 80s. Let’s exclude special houses for now. An apartment, especially the ground floor apartment in a two-family house, may have its justification, but honestly only if the concept of the fundamental planning of two residential units exists, in which you have a family bathroom and bedroom as well as two children’s rooms in the apartment. The latter two rooms were always appreciated by residents because they offered retreat and options for personal space. Upstairs, there was then a loggia for the second residential unit. The typical two-family house has become relatively uninteresting nowadays because people dislike living under one roof with landlords. Even holiday apartments with the landlords are unpopular. Life in a multi-generational house is now rare, as you want to grant your child freedom after graduation, and nowadays it’s also known that children need to leave, go out, live their own lives in order to learn to stand on their own feet. Whatever, of course there are exceptions, the youngest who never really grows up, and so on. The couple without hobbies and one child clinging because it is their life’s purpose, etc. But let’s get to the remodeling: half the apartment on the ground floor is just a compromise. A very expensive compromise. Today and tomorrow, i.e., later. Neither fish nor fowl, simply inharmonious. Family life equals zero because you want your peace. For that, you also don’t have an ear upstairs, so you can’t do daily chores while the kids are upstairs. Clear separation like in the 50s. These days, houses are built differently than decades ago. If you’re not the kind of “one” who belongs to that group, then just build it. Or question yourself why you want a house. People don’t dream of accomplishing something in life by building a house that insures them. Honestly? Our house is almost paid off. 132 sqm for two. One room could be bigger (we are under 60 and under 70). If we want to change something, our great house is our retirement provision. Nothing more, nothing less. So what leads to the poor design here: beforehand: there are houses that combine both. But not in the affordable, standard size, and amateur planning version. Your design is already bad even if one should not separate the floors. I’m not going to scroll back and collect quotes, but I know the justifications are posted here. Rather, you should really read and also understand the criticism. For the money, people just want something nice and simple, not insurance. That is available cheaper.