Is the floor plan suitable for a multi-generation house?

At the time, we built similarly with my parents and lived well for a long time in BaWü. Our plot was on a slope and about twice as large, so it’s not directly comparable. My parents wanted a simple basement room, which was out of the question for me, so we built them a large, fancy apartment of almost 100 sqm, including a roof terrace, on the upper floor or attic. Today, I think I might have overdone it, because my parents could have lived just as well in a well-planned 75-80 sqm, and as my mother got older, it indeed became too big for her. The fact that their apartment was on the upper floor (plus a long staircase to the house entrance) is something I would do again anytime for the following reason: As long as the parents were fit, they could easily manage the stairs to the apartment, which was their exercise anyway. When my father was no longer able to do that, he could hardly move around alone anymore, and we used an automatic stair climber or went down with him 2-3 times a week; after all, we lived together in the house. If you can no longer manage that, you usually cannot move around alone outside either, based on my own experience, incidentally also with my currently 90-year-old mother-in-law. I experience significantly more unsolvable problems on a mental level with elderly people. My mother then moved again to live with the grandchildren, also on the upper floor with a small bathroom. She always said that was better because she could hold on to something everywhere. What I want to say is: I would place the parents’ apartment on the upper floor and look for a nice floor plan with a beautiful view and a balcony; I would rather avoid a basement in flat country for cost reasons, but regarding floor area ratio and so forth for the plot, I have no idea. I would just free myself from the sometimes-read urge to definitely accommodate the parents on the ground floor, as their problems and risks lurk everywhere you cannot prevent them. Falls, etc., mostly do not happen at the house stairs but often at small carpet edges, different floor coverings, and so on. Your shown floor plan lacks any furniture that makes your individual life after all; as it is, it’s not really usable. Honestly, I don’t like looking at the floor plan like that; it’s not nice and should go back to zero. Don’t let yourselves be rushed; it takes time and also conversations. The children need direct access to the terrace; the parents (that would be the case for me as well) are fine with a nice roof terrace or similar. Maybe you could say more about the background, also regarding your parents.

The children need direct access to the terrace, the parents (that would be the same for me now) are satisfied with a nice roof terrace or something similar.

You are right about that. However, then the room layout cannot fit the area at all. Or you put the young people's bedrooms in the basement instead of the granny flat. But that doesn't make sense without a slope either, to dig up another 20/30 sqm on 475 sqm.

Hello,
would you like to provide the site plan (property) again? Also the orientation of the house (north/south) as well as the age of the seniors?
Do you have special hobbies? What do you like about the house?
Are you not planning a balcony or something similar for the upper unit?

Thank you very much for the feedback. I have attached the site plan of the property, hoping this will be sufficient.
For the upper floor, we actually have planned a balcony, I just forgot to mention it.

The orientation of the house should be towards the south, at least the front door and balcony are on the south side.

The parents-in-law are both just under 60.

Hobbies definitely include spending a lot of time with the children, so it is important to us that there is still a bit of garden available. It will probably not be more than 200 sqm.

What is that, for example?

A tip in advance: it is advisable to furnish the design plans yourself with to-scale furniture so that you can see where the shortcomings or potentials are (dining area size, TV distance, space in the children's rooms). You should definitely work on that.
Templates are suitable for moving around.

Oh sorry, I probably did not copy everything from the example text. There are no wishes from any magazines in the plans.

The idea of using to-scale templates is a good one, I will gladly have a look at it. Thank you very much.

Merciful goddess. This won’t work. The packing density of wishes in this design is too high. This is not a multigenerational house, but a two-family-plus-tenant house in the worst possible form. Go to an independent architect instead of a construction company botching something together and then having it scaled down. And cut out the tenant apartment, whose integration probably caused the necessary downsizing of the design in the first place. Build with just one normal stairwell and a spiral staircase in the upper/mansard floor maisonette.

Thank you very much for the feedback.

Maybe I’ll briefly tell the history of how the plans came about.
The first plan was an asymmetrical semi-detached house on a slab and was significantly over budget. Requirements were 80sqm for the parents-in-law and we calculated 135sqm and up for ourselves. We are currently living in 100sqm in a 3-room apartment and are practically missing two rooms (1x children’s room, 1x office). In relation to the plot, the planned house was unfortunately also too big.

For the second plan, we then decided that the parents-in-law would get the ground floor (they don’t want to move into the basement) and we would take the upper and attic floors, since the parents-in-law don’t want to climb many stairs in old age. To still have the character of a house, we didn’t want to have only one floor for ourselves.

However, a basement was then planned because we need storage space. We have already had to rent an external storage space because our current basement compartment from the apartment has become too small (and that was not even 9sqm). This was the plan with the 100sqm floor area and the stairwell was not yet partially integrated. This plan was also over budget, so we looked for potential savings together with the developer.

Until then, there had been no talk of a tenant apartment — the idea was introduced by the developer to generate additional rental income.

The result was the third variant with 90sqm floor area and the partially integrated stairwell, which saved costs again. Additionally, the stairwell from the "stair shaft" from the upper to the attic floor was removed and centrally placed in the apartment, which saved costs again.

We have currently decided against a tenant apartment, but it is mistakenly included in the above-mentioned plans. In fact, we are only having the preparations made for a tenant/holiday apartment so that a possible expansion is simplified since the connections would already be in place.

What would a floor plan from an independent architect cost? On the internet I have read something about 10-15% of construction costs.
What optimizations do you see?

Urgent recommendation from my side .. e.g. for the furnishing of the bedroom on the ground floor. I would also be interested, because there must be at least 4 parking spaces with the option for 2 additional spaces.

In fact, we would have four parking spaces -> a double garage + the two spots in front. I attached the plan further up.

That will be a problem with not even 500 sqm.
I assume that south is also at the bottom, where it belongs, and the basement apartment is only there to compensate for the oversupply of the basement. I can't think of a quick solution off the top of my head.
For the existing ground floor, I would extend the hallway a bit, plan a built-in wardrobe as a cloakroom at its end, and swap the functions of the bedroom and office (adjust sizes) so that the bathroom is next to the bedroom. Then adjust the door to the office according to the living room furnishing. The extended hallway also benefits the dining area because it adds structure.

The children's rooms are not too small. However, you should make sure that deep cabinets can also stand behind the windows, which means: move the windows apart. I would also avoid floor-to-ceiling windows because they affect privacy. After all, the neighbor could look under the belt line there. Give the kids low built-in cabinets under the slope at the knee wall or place an upside-down Kallax there, so the low knee wall is well utilized.
However, these tips do not solve the parking space problem.

Currently, we have only decided to prepare a basement apartment. It will presumably be used mainly as storage space and possibly as a hobby room / party cellar. If we need to generate additional rental income, this could be converted into a basement apartment / holiday flat.

Thank you very much for the tips regarding the windows, I will make a note of them ;-) The current children's room has about 15 sqm without sloping ceilings, with sloping ceilings we would then be "only" at 12 or 13. But I lack experience with sloping ceilings.

Regarding the parking spaces, we had thought of a double garage and two spaces in front of it.