ᐅ Single-family house design, 250 m², 2 full stories with a hip roof

Exactly that large bedroom should be divided.

The children's room would then be directly adjacent to the parents' bedroom.

I would like to store beverage crates in the drawers.

A door to the kitchen from the gallery seems reasonable.

In a new build, you wouldn’t plan a technical room like that, unless it’s a 120 m² (1,292 ft²) house.
Then plan a proper staircase to the attic if that is your only storage room.
Also, build in the wall for the second children’s bedroom right away. It makes the master bedroom cozier and prevents dust later on.
Better position the children’s bedrooms accordingly.

Offers at that price.
Have the offers checked. Some items are missing or are based on standards from granddad’s time in the 1950s.

https://www.hausbau-forum.de/threads/warum-ein-Hausbau-fast-immer-teurer-kommt-als-kalkuliert.16237/page-37#post-287827

https://www.hausbau-forum.de/threads/liste-der-anfallenden-Baunebenkosten-bauseits-teurer.9737/

https://www.hausbau-forum.de/threads/baukostenentwicklung-noch-normal.28743/

Regarding the ventilation system
https://www.hausbau-forum.de/threads/zentrale-oder-dezentrale-Lüftungsanlage-wer-hat-Erfahrungen.26903/

You can easily reduce to 200 m² (2,153 ft²) without any disadvantages.

Sometimes it seems like you are building a 100 m² (1,076 sq ft) house.
A crate of drinks in the kitchen
Storage for a party in the hallway or on the terrace?
Does the man hang the laundry in the evening, or does the woman use a stool?

What do you mean by a reasonable staircase?

Of course, the layout can be simplified, but why would you want to? The budget is well within limits. Space can be used very flexibly.

So, to summarize:

- Door to the kitchen from the hallway.
- Possibly a pantry (in the relatively large kitchen, there is plenty of space for gatherings, which are exceptions in my opinion).
- Larger utility room.
- Bigger children’s bathroom.
- Wall to divide two children’s bedrooms from the start (could be used as an office).
- A “proper” staircase to the attic?

No retractable ladder, but a standard one like from the ground floor to the upper floor.
Have you ever struggled to carry a bulky, heavy box up a retractable ladder?