Ground plan design single-family house 165 sqm without basement on 400 sqm plot

what about this idea?

Well, the living-dining-cooking concept is also somehow very cramped, all in a line, with a block next to the neighbor's garage from the dining table. And above all, even less of the house area is used for this purpose than in my current design, where just over half of the area is used for this purpose. In terms of layout, yeah, maybe with a platform staircase. I don't like the upper floor. Dressing room is missing, bathroom too small, washing laundry where it arises and where it should be put back clean is missing. We are so tired of carrying mountains of laundry down from the upper floor to wash it, and then carrying it back up clean, to be able to wear it again. And the cycle repeats. So there are still a few central things missing on the upper floor that we have on the specification sheet. Otherwise, yes, not bad, but it doesn't suit us as it is now without changes. The length also leaves room for another meter of property to the back.

Also the long side still a meter of land to the back.

No. They are exactly 12 m, just like your drafts.

That has to be respected if it's not yours. But a few objections/questions

with block on neighboring garage from the dining table.

For that, you don't stick onto the neighbor's property and still have enough space available for a hedge so that you don't see the neighbor.

this purpose

for this purpose

Which purpose?

We are so tired of lugging the laundry down in heaps from the upper floor to wash it,

Think of the thousand steps... and please don't overdo it when planning a house - you do yourselves a favor if you stay realistic.

Ohohoh, sounds very pessimistic. I hope it’s not too unrealistic to wish for a laundry room on the upper floor. If it is, might as well leave everything as it is. That would be even more unrealistic. :oops::eek::D

Before we misunderstand each other now…
To your questions

Garage aligned flush with the house or set back?

is clarified with this specification:

Driveway or space in front of the garage at least 6 m.

rather modern construction style.

I don’t really find that the house is modern inside. An open space and, how do you say it so nicely here in the forum (well, not me), an aircraft carrier do not necessarily make a house modern inside.

43.5 sqm + 4 sqm pantry sufficient as a “multi-purpose room”?

One cannot say that as a principle, since the layout plays a role.
43 sqm can be enough, but then please not with an oversized island that needs 60 sqm of space, at least a kitchen that allows the flow of the daily activities. Because here it is docked exactly where one actually wants to enter the kitchen on a short path. The kitchen is a loop with a bottleneck that leads to a room that should be accessible quickly (meaning from the entrance, viewed from the hallway).
Regarding the dining area: 3 meters width, that is a given. Then also ensuring that you can reach the terrace door without slalom. The living room should get a TV spot that is important for you. I don’t see any of that – too tight and too long.
I would therefore shape the multi-purpose room more like an L: dining in the SW, kitchen in the S, relaxing in the NW. Above that, ideally the bedroom.

Same floor plan possibly mirrored?

No, the floor plan has too many flaws for that, even if your wishes are fulfilled, they are still there. And you are here so that these flaws can be pointed out to you.

But then office on the south side, sun all day, blinds always down. Same thing upstairs with the bedroom in summer at least.

Well, in winter you will be glad when enough daylight comes in there. Guests will certainly also prefer sunny. Just to note: your dad’s room is also on the south with few square meters!
I would always assign side rooms, if possible, to the darker location, living spaces to the brighter one. Shading is a topic anyway, and if you are aware of it, you can plan windows quite well so that you don’t have to cook.
Upstairs I would try to assign the “narrower half of the house” to the side rooms, because they can handle it. Bathroom, laundry, and dressing rooms suit that well. The bedroom then in the NW. Children’s rooms in the bright south then with the 3,x meters. That has to be looked at.
Of course, not everything can be implemented as in theory, but at least that is how I would initially arrange the rooms.

Yes, great thanks for the detailed analysis. I can generally agree. It all sounds plausible. It also sounds a bit like, if you already want to keep the straight staircase, then keep it but arrange the rest differently. One thing does interest me though. What would be modern then?