New construction project single-family house in the Bergisches Städtedreieck

So, here comes the first draft of the upper floor...

Even on the ground floor, the open plan kitchen with a suggested kitchen island looks very tight, but it is always difficult to judge without measurements.

Overall, I fear the staircase is too short and thus everything fails. The upper floor also looks very cramped; where is the storage room supposed to be accessible from? It can only be accessed from the bathroom.

The measurements of the cabinets and the kitchen island in the kitchen are not set in stone. The kitchen can be adapted to the available space. I am aware that there must also be enough space between the kitchen island and the cabinets. We don't need a large kitchen island either. That will be adjusted individually. I just wanted to give a rough idea of what could go there.

On the upper floor, behind the railing (approximately in the middle of the stairs), there is an entrance door for the storage room. It is not necessary for the entire stairway to remain free. The length of the stairs has been inserted from the app and has a normal length (according to measurements from the app: 3m long, 1m wide, 14 steps). As already mentioned, this is only an amateur draft. The final measurements will be done by an architect.

Upstairs, behind the railing (approximately in the middle of the staircase), there is an entrance door to the storage room.

And, how are you supposed to get there, please? And here are some usual standard values for stairs: and there you see that for a standard room height of about 250 cm (floor-to-floor height = 280 cm), about 360 cm of stairs must be calculated. If it is to be very comfortable, then even well over 400 cm. from:

for a standard room height of approximately 250 cm (floor-to-ceiling height = 280 cm), about 360 cm of staircase should be calculated.

I agree with Escroda's placement suggestions. I don't see any other reasonable solutions here. You should start an appropriate floor plan discussion in the dedicated forum.

I wouldn't have taken the previous drafts seriously at all, since the core question was about the location and the staircase alone makes the design unfeasible. Therefore, you might be better off waiting for the design from your architect / general contractor.

That’s unfortunate: You chose the wrong subforum here…. we have a special floor plan forum for this…

Separated living area for
the grandparents: living room with kitchenette,
bedroom and barrier-free bathroom (here about 45m2).

The grandparents are moving from a three-room condominium into this one living room. They don’t want to take much with them. There is also consideration about leaving out the partition wall between living room and bedroom, although that will have downsides too. Somewhere the clothes have to go, so a wardrobe still needs to fit.

Yes, I think so too. This definitely needs to be improved. Because the walking aid is already in use.

Even before I read the last sentence about the walking aid, barrier-free design kept coming to my mind. At least the rooms should be low-barrier. I don’t see that at all. I don’t see a wardrobe or any cabinet in the living room, I don’t see a dining area. The rooms are already a challenge even for agile people. Furnished, quite cramped, I don’t see room for a walking aid, I don’t see many things: coat rack, enough space in the bathroom. …

We don’t need a large cooking island either. That will be tailored individually. I just wanted to indicate roughly what could go there.

I see it as initially not feasible:
the problem with your placeholders is that they don’t work. Also the staircase, even if it’s from a program, is too short for real houses. There are programs where you have to scale the objects and there are minimum dimensions you wouldn’t want to have yourself.
One of two passages in the kitchen should be at least 80 cm wide, if there is only one passage, then at least 1 meter. A staircase with a normal ceiling height has a minimum length of 3.70 m (with kbt09 even 4.10 m), a hallway needs a certain width to accommodate the door and movement.
A door is represented with the door leaf so you can see where someone might get hit by it or where it stands in the room when open, don’t ignore that. Many things depend on each other, and when planning, the door affects a wall length, this length influences the placement area, the placement area influences workflows… and that for every single room.
If I take the staircase in relation to the 20 sqm senior multi-purpose room, something is wrong with its measurements there. Looking into the kitchen, you can see that you can’t open the side-by-side fridge door from the front. And if you just wave that off and say to yourself “there will be fine-tuning later, these are just placeholders for now”, what possibilities will you have later? Hardly any. Possibly removing the island and unnecessarily wasting space.

I just skimmed the thread here earlier and immediately thought that 40/45 sqm extra on the ground floor for the seniors is not feasible because of the reduced building envelope. However the building envelope may turn out in the end: It will be rather difficult based on floor area, probably only achievable through an overhang on the ground floor in a city villa, otherwise the rooms upstairs will become too big.

Since the plot facts are quite fixed and you want a certain size on the ground floor (half a granny flat), I wouldn’t restrict yourself too much with wishes like city villa or solid construction. Timber frame uses less wall thickness, a city villa carries a disadvantageous corset with max. 2 storeys, while a gable roof house might offer an attic studio for the kids or as a parents' level.
Also, I would give the seniors their own entrance door. And/or plan a vestibule, because when elderly people go through a door, it usually takes longer. A separate granny flat also offers additional KfW conditions.

My question: do the seniors already know how lucky they are that you are including them in the plans?
70 years old isn’t old nowadays. You don’t want to find yourself in a tiny hole at 70 just because you think that babysitting the children will be practical?!
I ask because I truly don’t know anyone over 70 who wants to live dependent. And in our new build area there are many over 70
and as a consequence, the house can be planned in a completely different way if you face reality.