Floor plan single-family house approx. 140m² - separable staircase

I have to ask a dumb question, on the one hand you write that you want separated residential units or a separable staircase. On the other hand, you don’t plan it through to the end (bedrooms downstairs too small, front door opens onto the staircase, presumably missing kitchen connections upstairs, etc.)

On the one hand you say you have too little space downstairs and too much upstairs, on the other hand you reduce the ground floor with the setback.

I don't really get it either. Somehow I also find the rooms quite narrow. Starting from the kitchen to the [Speis], then the comparatively long hallway... I somehow don't like the floor plan.

There are really quite a few things that haven’t been fully thought through. Yes, a small fireplace might be about 50cm deep, but keep in mind, you can’t just slap it against the wall, it has to have a certain distance from the wall (20cm) AND from the furniture (80cm) in front. So, that only leaves you 2.50m for the dining table including chairs. And not to forget, the heat radiation from the stove could quickly make it uncomfortable at the table if you’re sitting right up close in front of it. The people sitting with the chair against the wall will also not be happy if they always have to squeeze past to get to their seat. I’m absolutely pro-fireplace, but in this spot it is misplaced. And don’t forget, you might be planning for another child, which means either a stove guard in front of the fireplace (space?) or a burnt child or the stove stays off and is pointless. By the way, the 4m is the raw construction measurement. You also have to subtract 10cm for plaster, wallpaper, and baseboard.
Also, the concept of possibly living downstairs later: either do it properly or not at all. If you square off the ground floor as well, you gain space and will probably even save some money.
And yes, I know what it’s like with 2 children and one bathroom. I even know what it’s like with 3 children, so that’s why I recommend reconsidering the bathroom concept, or do you want to send your kids out of the warm bathroom after their bath just so they can use the toilet? If you want, you can plan a second toilet upstairs, but a toilet still belongs in every bathroom, especially when there are children. Also, something I just realized: the shower won’t work under the sloping roof either.

I completely agree with Manu1976. Either you plan the ground floor for old age or you don’t. What you are doing now is making compromises. This is not a problem at all when you are young because you have no idea what it is like to move around in such a small bedroom (for example) as an old person.

By the way, I would rather leave out the step down and instead put the pantry right next to the kitchen. Having to go through two doors across the hallway to get the pasta would annoy me.

I still don’t understand the "separable staircase"; where or how is it supposed to be separable? If the house is later to be optionally divided into upper and lower parts, I would design the entrance area so that this separation is possible.

Basically, I have the impression that you don’t want criticism but agreement.

:
It is being built massively with Architekt and is intended to achieve KfW70 standard. However, not at any cost.
We definitely want a fireplace.

With KfW 70 and a water-based fireplace, I assume the fireplace is supposed to support the heating circuit. It is not suitable for heating the room and would be money thrown away.
The costs for the piping and system adjustments are certainly planned in the budget, as well as the chimney draft and the stove.

How high are the costs calculated by the professional for this?

Regarding the rooms: We also built a bedroom on the ground floor to be able to live downstairs in old age. However, it is larger because one might need devices or aids in old age.

The last post suggests many compromises. I dare to doubt whether it is advisable to make such an expensive compromise.

Is this floor plan the first draft?

If you look at the posts from the OP, this is not the first draft. The previous ones were really bad, compared to which at least some livability can be seen now. Although I have to say that the OP should think about to what extent and why a separation should be favored later. For me, all the rooms are a restriction in favor of the later separation. And yes: what's the point of the basement?