Floor plan single-family house, 1.5 floors, 2 children's rooms, 2 offices - is area usage optimal?

Kitchen recess: niche for food (not walk-in, but a compromise instead of a storage room, since ours is in the basement)

Living area as a passage room: desired by us, since we don’t often go from the upper floor / hallway to the kitchen. Also, this way we have more partition walls in the kitchen

With the niche you reduce your usable space, because you also have to be able to access the niche in the kitchen. I strongly recommend planning this kitchen space properly.
And also the furnishing of living / dining with walkways to the terrace from the kitchen.

The idea, as always, is to swap living and cooking, which also creates a quieter corner. As the hallway is currently, it could possibly be narrower, but it’s not easy to assess because intermediate dimensions are missing in the floor plan.

as long as the OP does not provide credible information.

Well, with the popular phrase of one point five floors, we have our generous day: but at least there is 5.80 m eaves height (albeit, as usual, without specifying the reference point). Even if the SD30 specification probably again mixes development plan requirements and personal decisions, you can still make something out of it: namely that a knee wall of 220 will very likely be possible, provided a second full floor is permitted. Based on experience, I assume that the general contractor’s planning indifference does not go so far as to have a design created that is not approvable from the outset.

If there really is no ridge height restriction named, my cautious suspicion regarding the gable width was probably wrong, and the general contractor simply rummaged in his drawer for a basis that fits into the budget given to him (because as is well known, a general contractor does not care when the client will have money again for flowers and a DIY terrace — the main thing is that the budget is turned into a contract sum). He will be confident that he can provide roughly 160 sqm plus basement for that (or estimate the clients’ creditworthiness so that an appropriate additional injection of funds is possible). Whether the garden becomes pretty or the client has to do crowdfunding with Aunt Frieda and Uncle Erwin for a used kitchen is irrelevant to the general contractor. You can also wait for admission on a Euro pallet in front of the front door ;-)

That is one of the most curious reasons I have ever read here – just as an aside.

Basically, it’s a solid thing. Unfortunately, I still can’t warm up to it. The kitchen is too cramped for me, the living room isn’t cozy, the furniture in the dining area looks suspiciously small, the hallway too dominant. Hopefully, the bathroom upstairs will also turn out nice, and I don’t find the corner in the hallway very elegant either. None of these are deal breakers, but I somehow miss the flair of a modern house.

We will reconsider the question about the kitchen niche and the kitchen door. Thanks for the feedback. What would be your suggestion for the hallway? To widen the guest toilet at the expense of the hallway and possibly set up a separate wardrobe?

The building mass is, in my opinion, also unfortunately placed so that the garden is maximally chopped up. I would go more in width instead of depth.

Do you mean by "go more in width" to give the house a few meters in width or to rotate the house 90° (with the eaves facing the street)?

Well, having our generous day with the popular formulation of one point five floors: at least there is 5.80 m eaves height (even if, as usual, without specifying the reference point). Even if the designation SD30 probably again mixes development plan requirements and personal decisions, you can still make something out of it: namely that a knee wall of 220 will very likely be possible, provided a second full floor is permitted. Based on experience, I assume that the planner's indifference of the general contractor will not go so far as to have a design created that is not approvable from the outset.

If no ridge height limit is actually specified, my cautious assumption about the gable width was probably wrong, and the general contractor simply rummaged in his drawer for a basis that fits into the budget given to him (because, as is well known, the general contractor doesn't care when the builder has money again for flowers and a DIY terrace – the main thing is that the budget is converted into a contract sum). He will be confident that he can deliver about 160 sqm plus basement for that (or assess the creditworthiness of the builders so that an appropriate top-up is possible). Whether the garden will be pretty or the builder has to do crowdfunding with Aunt Frieda and Uncle Erwin for a used kitchen is irrelevant to the general contractor. You can also wait at the front door on a Euro pallet ;-)

I just checked the development plan: Max. eaves height 5.80 Max. ridge height: 9.00 (both from BZH). If my mathematical knowledge is not completely lost, we would still have quite some room regarding the gable width up to the 9.00 m.
What do you think is the advantage of 2 complete full floors? Besides the possibility of having a "normally" high window lintel on the eaves side?

I can't entirely dismiss the suspicion of a "floor plan from the drawer".... Although that doesn't necessarily have to be a bad thing – especially since we don't have any extravagant wishes :)

What do you think is the advantage of 2 complete full floors?

Sorry, it’s not about what has advantages if you don’t even have the option. Check again: what is allowed? Is there an l or an ll?