Location of city villa or single-family house on 500 m2 plot - rectangular

My view:
with children = 2-story
without children = 1.5-story

Ok, could you maybe explain the reasoning behind that a bit?
So far, our boy has found the idea of sloping ceilings really cozy and would prefer to live in the converted attic and never come down again.

I understand that the idea of children doesn’t necessarily have much to do with reality. But so far, my idea was also that children can still cope relatively well with slopes: they are smaller at first, need less "waist-high" furniture, and generally prefer to spend time on the floor anyway...
Ok, if a bunk bed has to go in, a high wall might certainly make more sense, but you don’t have to plan for that.

I, on the other hand, need my 2.35 m high wardrobe, the 2.37 m high shelving unit, and want to hang a few things on the wall for which sloping ceilings are simply impractical.

But the house is not supposed to be just for me. That’s why a gable roof is certainly an option for me if there are decisive advantages.

By the way, according to the builder, it isn’t much cheaper (3,000 EUR for 150 m²).

Best regards

Tolentino

Ok, can you maybe explain the thought process behind it a bit?

As an adult and a child I wouldn't have a problem with it either, but as a teenager I would (the older you get, the more space you need), I want to get the maximum out of my room and the one and a half floors would limit me there.

I see it the same way. Your house will be about the same size as mine: 11x10m. We've also planned 2 children's rooms there. If I imagine it now with sloping ceilings and smaller, etc. - that would be noticeably less. Ok - complaining on a high level, but if you already have the choice...

Yes, I actually see it the same way. Just wanted to make sure I’m not forgetting some brilliant advantage of [Satteldächern]. The convertible attic doesn’t seem to make much of a difference.

The expandable attic doesn't seem to matter that much.

It can be neglected. That would be just an attic peak. The attic of the hipped roof is even bigger. But overall, the costs are of course higher - obviously.

So far, our boy has found the idea of sloping ceilings really cozy and would most like to live in the converted attic and never come out again.

A straight-walled upper floor has the least treehouse appeal

What would be a usable knee wall in your eyes? 1m?
Well, I am actually someone who, because of the usability of the space, tends to advocate for 2 full floors.

I would not limit the concept of usability to the idea that all corners must be suitable for broom closets – that strikes me as too dogmatic a paradigm, and I see it as unnecessary.
I see a knee wall as optimal exactly when it fully substitutes a dwarf wall – that is, no more and no less: because only then do you not need to combine the two (which I also consider highly avoidable). With regard to the simpler closure of the thermal envelope, it is more practical to have a knee wall and an attic instead of a dwarf wall and a storage space (or dwarf wall, storage space, and attic). As a benchmark for the clear knee wall height, I would orient myself on parapets or bed headboards.

Without a knee wall or dwarf wall, I would not operate in a converted attic. The most economical roof types are the shed roof as a truss construction with an open underside, and in various constructions, the gable roof. If it had not disappeared from the minds of zoning planners, the mansard roof would actually come closest to the usage wishes of most homeowners – however, it is significantly best suited for rectangular floor plans, as breaks are its Achilles heel.