Floor plan of a two-family house with a stepped floor - too compact?

I think the data (heights) will fit (except for the budget). While reading, I thought: well, even if adults don’t like slants, you can still give the children nice rooms under the roof. But then I also thought that the roof terrace does make some sense if you live on the upper floor and give the garden to the seniors. But I only see the roof terrace being used by the children. I don’t know if it’s really used like that. Also the gallery… that’s a cozy area for the children, but a no-go zone for adults ;) To sort it out for you (apart from the floor plan): You’re giving up a larger footprint so there is still some garden left, but then you don’t really have anything from the garden, or the remaining piece of garden now has to be maintained by the seniors. Does that make sense? Basically, it’s going to be a two-family house and remain a two-family house. A little bit of garden share for some parking spaces and that’s it. Then it is assumed that the 30-year-olds have the same living needs as the seniors over 70. The seniors’ apartment is nice, but I find the 8-seater dining table somewhat out of place and too large. The bedroom is a bit cramped. A small dining table makes sense in the kitchen. Guests can be accommodated more cheaply and with more privacy in a hotel. For “later,” the bedroom partition wall could be removed… But: I want to throw another suggestion into the ring: Increase the footprint after all, put a kitchen-living area, WC, and utility room on the ground floor for the young family, then adjust the upper floor on the footprint with a small living room and children’s room. The bedroom will probably also fit there. Just as an example in a sketch (without binding measurements or anything, just as a rough size indication)

I would arrange for a drug test at the building authority and the legal department – as they say at the station, you can look at me for that.

I can only say that the previous "exploitation" of this regulation has been implemented consistently in my opinion, but of course I agree with you that it can be abused in doubtful cases. In any case, it helps the supporters of stepped roofs to generate additional living space without inclines.

So I can only say that the previous "exploitation" of this regulation has been implemented consistently in my eyes, but of course I agree with you that in case of doubt it can also be abused.

Unfortunately, it does not need any doubt to become abuse. A recessed top floor means a factual roof pitch of 90° on all edges without setback – and here I have to remind you of Kant’s categorical imperative in protection of neighbors (while most questioners here are very sensitive to the full shading of their own property).

In any case, it helps proponents of the recessed top floor to generate additional living space without slopes.

Sealing means more than just covering grassy areas with concrete; it generally concerns the necessity of moderation in how many inhabitants per hectare a community exposes nature to. It rains the same for everyone, but wastewater, for example, occurs in quantities dependent on population. With all understanding for home ownership wishes, it simply cannot be allowed for house builders to stack themselves on as little land area as possible.

I don't even know where to start with this not working out. So I'll just pick out two appetizers: the maximum 7m eaves height is definitely violated here, and you probably also need to consider at least three parking spaces.

With the stepped story, the max. eaves height of 7m is definitely not violated. Our general contractor and we ourselves have consulted with the building authority and were confirmed that we can build the house that way. The stepped story does not count as a full floor if at most only 3/4 of the floor below is built upon. The regulations in the building code (at least in NRW) have even been relaxed in recent years. The stepped story does not have to be 1 or 1.5m away from the outer walls of the floor below. It is sufficient if only 3/4 is built, meaning the STG can be attached to one outer wall. A few plots away from us (same building requirements), a house with a stepped story is also to be built and the builders have already received the building permit from the building authority.

We will have two parking spaces on the east side of the house and one is to be built in the north or west.

So, now that we've gotten the appetizers out of the way—what's for the main course that could give us indigestion? :)

For a house of this size, I see the targeted budget as too low.

..in addition, about €65K funding comes on top, I had forgotten to add that.

What requirements do your parents have for the granny flat? exact room program like bedroom with 4 m running wardrobe living room with XXL sofa, bookcases approx. 5 m ceiling high. Also, what handicaps should they be able to manage in the apartment. The same applies to you. Create an exact room program with the necessary furniture and dimensions. Draw all furniture to scale including movement space. e.g. dining table A minimum movement space of 80 cm from the edge of the table is assumed. So a table 1 m wide needs at least 2.60 m width space. This way you see your living space is too small. I would plan the open-plan room in the top floor, so you have direct access to the outdoor dining area.

Thanks for this tip. We will reconsider it. The general contractor and we have for simplicity planned the apartment on the ground floor exactly like the apartment on the upper floor, since we plan to move to the ground floor in a few years (at least that is the plan). My parents do need quite a bit of space as they regularly receive visits from their children and grandchildren (they live close to the new development area).