Total budget without building plot: approx. €450,000 (and yes, we are willing to do own work)
Which ones? Flooring and painting?
Seems a bit tight to me now, but others can surely say more about that.
Me too!
Style, roof shape, building type: Basement with living space (approx. 50%)
Basement, floors: Basement + full floor + attic
A basement is a must because of the slope.
A staggered floor like Bauhaus edition I find too expensive.
Living area approx. 150+ square meters (with at least 3 children's rooms)
You need a tightly planned room concept…
we would definitely build a basement (initially not livable, maybe later 1-2 rooms with sunlight due to slight slope)
… for example, there are no children yet. Therefore, a solid compact gable roof house with a basement, with two finished living/sleeping rooms in the basement for office and child, so that it does not count as a full floor.
Attic then expandable, so that more children's rooms can be created there later.
Assume €2,500 per sqm of living space. Since I assume that €450,000 also has to cover ancillary construction costs, €400,000 remain for the house, i.e. 160 sqm including basement.
80 sqm living area on the ground floor, underneath 25 sqm of utility space, 40 sqm for 2 rooms and guest bathroom, and a "cheated" half area for the office.
Attic therefore not developed for the time being, but prepared.