Ground floor approx. 100 sqm, upper floor expandable (planned bathroom, 2 children's rooms, 1 storage room)

A tip, because I also have this stairwell with an unfinished attic as a storage room: Use a patio door as the door to the cold part. At first we had a wooden door, which warped so much in winter due to the warm-cold boundary that it hardly closed anymore. It has now been replaced with a patio door, and it works great now. K.

If I don't have a distortion in my view, the position and the opening for the staircase do not match the staircase that is drawn on the ground floor.

Is it financially settled that a later expansion of the roof is included?

Yup, there is a building savings contract shortly before allocation, another building savings contract in a few years, and a one-time payment of 10k also in a few years, which are not included in the current financing. The expansion will take place at the earliest in 4-5 years and can be done as DIY work (family + friends). What matters to me now is to know how it should be later, in order to do the right preliminary work already now that fits the later plan and does not have to be changed again later.

A tip, since I also have this stairwell with an unfinished roof as a storage room: Take a patio door as a door to the cold part. At first we had a wooden door that warped due to the warm-cold boundary in winter so that it barely closed. It was now replaced with a patio door, which works great now. K.

Yeah thanks for the hint. Exactly because of this issue, we chose the MZ door made of plastic (U-value 0.93 + g-value 50% and warm edge). It could later also serve as an exterior door in a possibly planned shed.

If I don’t have a kink in the optics, the location and the cutout for the stairs do not match the stairs drawn in the ground floor.

I looked again, for me it fits. But I would not rule out that I have a kink in the optics.

My concern now is to know how it should be later on, in order to do the right preliminary work already now that fits the later plan and won't have to be changed later again.

Quite late, I think.
The floor plan has already been discussed, and I find the sense of some things quite doubtful. But don't you want at least to have the doors to the rooms open inward as they should and not into the hallway? Otherwise, it will be a constant clatter of doors. How big are they actually and how big is the front door?

What do you really need on the upper floor? Where was south again?

The stair opening is dimensioned at 2.5m. However, your staircase is 3.9m long. With a floor structure in the upper floor of about 30cm, this results in a passage height of only about 1.3m. For the usual 2m, an opening of 3.5m is required.

Pretty late, in my opinion.
The floor plan has already been discussed and I find the sense of some things quite questionable. But don't you want at least the doors to the rooms to open inward, as it should be, and not into the hallway? Otherwise, it will be just a constant clattering of doors. How big are they actually and how big is the front door?

What do you really need upstairs? Where was south again?

Planning the upper floor now is actually quite late if it is only supposed to be fully converted in a few years? Hmm, I see it a bit differently. The usefulness of the ground floor is questionable for many, I am aware of that. The fact is, though, that it works for us and after all, we will be living in the house. The ground floor is not really up for discussion anyway; for that, it is indeed already too late. A little anecdote on the side: I once talked with my parents about the forum's criticism points and they could report regarding the utility room door that homes built in the old new development area were completely without a utility room door because they didn’t even know about this use of the utility room. Seems to be really a regional phenomenon of the North. By the way, I know three other floor plans from the neighborhood; two do it the same way as I do, the third has an open kitchen but still uses the utility room like we do. Nevermind, maybe a bit odd and not up-to-date, but I stand by it

So far, we want all the doors on the ground floor to open into the hallway because that way we can use the rooms (rooms 5, 6, 7 are quite narrow and if the door opens into the room, it will make it cramped. At least that’s our idea) better. But we can still change that since we order and install the doors ourselves. The front door is 1.60 m x 2.20 m and the room doors 0.865 m x 1.985 m.

The terrace is on the south side, I had marked it on the upper floor.

But as I said, I am only concerned about the upper floor. There we want 3 living rooms, 2 of them preferably somewhat larger than the 3rd room + bathroom and a small storage room.

The opening for the stairs is dimensioned at 2.5 m. However, your staircase is 3.9 m long. With a floor structure in the upper floor of about 30 cm, this results in a clearance height of only about 1.3 m. For a usual 2 m, an opening of 3.5 m is then required.

Ah, that’s what you mean. Yes, it might not be exactly to scale. The floor structure will probably be more like 10 cm. Underfloor heating, dry screed, flooring. A cousin has 9 cm. Also a wooden beam ceiling.