Single-family house 175 sqm without basement, too big?

I also like the suggestion from . You just have to be careful whether it also works statically.

That water pipes and statics must still be checked for every design is beyond question for me. As a layperson, I cannot and do not want to judge that at all, so it is already clear to me that this can still throw a wrench in the plans.

I as a layperson cannot and do not want to judge this at all,

Of course not in detail. But already aiming roughly in the right direction is not rocket science. When it comes to statics, you first plan all walls thick just in case and are sparing about stacking them on top of each other. Wastewater is also simple: you simply place a drain at each sanitary fixture. In the worst case, each one goes straight down individually. More economical is to bundle them and have them fall collectively – a sufficient slope is also needed sideways up to the collection point. Drawing a fan spider in a bathroom layout that bundles all drains should be manageable even for a blonde in her first year of apprenticeship. The goal is not to replace the expert engineer. But just like in the dance hall of , a suspended ceiling in the rooms below the bathroom would hardly be avoidable.

What concerns me most is the toilet. I have now overlaid the upper floor and ground floor plans, and you can clearly see the deviation between the two walls. As a layperson, I can't really assess whether it is possible to somehow manage in the ceiling to lay the toilet drain pipe far enough towards the top of the plan so that no boxing in the hallway on the ground floor is needed. Unfortunately, I guess I’m a blonde before my first apprenticeship.

I can't get excited about this narrow stair hatch, unfortunately. I think it looks pretty slapped together in reality. Even if it fulfills many wishes, is it worth it?

I would go back to the starting point here and consider what you really need, placing the additional wishes as optional. By the way, what is the budget for this?

In my opinion, your space requirement on the ground floor is higher than on the upper floor. Planning such a large storage room and then an additional storage space – I would have to have a lot of extra money. Is that the case? If not, it’s worth considering integrating the garage roof into the ground floor planning and making the upper floor more compact.

To what extent would covering the garage enlarge the ground floor? Or do you mean that the garage would practically have to be located in the basement?

The problem is that "extras" are more expensive than enlarging the entire house’s footprint. At the very beginning, I saw a picture of a house with a large flat-roofed bay window wrapping around the corner on the ground floor. I really loved that! As a result, the ground floor is also larger than the upper floor. But that is more expensive than enlarging the ground and upper floors equally.
I don’t think the upper floor is actually as big as you think... Yes, one can argue whether a children’s room needs to be almost 20 sqm. Yes, one can debate whether this storage room is necessary. But the fact is that we need storage space, a workspace for my partner, and an overnight accommodation for the parents, and that in a bed! Unfortunately, this is medically absolutely necessary.

Of course, one could also consider putting the office upstairs instead of the storage room and enlarging the utility room on the ground floor as storage space instead...