First bungalow, later two-storey

Ok, I am slowly beginning to understand the issue. I hadn't thought about sealing; that would also have to be done with a flat roof... If I build a pitched roof on top, can it still be used later? So if I completely convert the [og], can the pitched roof somehow be "lifted" (with a crane) and put back on the [og]? Then I would only have to pay for it once in the long run.

The costs are many times higher than if you simply build an SD with 45°... whether with or without a knee wall is up to you. You can also live in the upper floor later without a knee wall.

To lift it, you would have to cover it (=new roof tiles), redo the vapor barrier, finance a crane for several weeks... and then it is still unclear whether it is possible and your roof structure won't be damaged.

Great, thank you very much for all the information. I have now thought about the following:

Basement as a white tank, ground floor developed. On top a gable roof, insulated, nothing developed. What would be the approximate price for a floor area of about 9m by 10m?

If you want to save money, skip the basement -.- (depending on the land value). So what you have to do: rough electrical work, heating, rough plumbing

Hi,

by raw electricity do you mean that I lay the main line upstairs, or directly lay out all the electrical wiring upstairs?
Heating upstairs? So directly laying the underfloor heating there as well, or just the main line upstairs (I had already considered a supply shaft).

Thanks

Complete electrical installation is not necessary - especially when you are only doing drywall work on the upper floor, you can certainly find a concept where outlets are only in the partition walls. If you leave out the drywall panels, you can then conveniently run the cables later up in the ceiling. In principle, you then have a large space upstairs where you look at the vapor barrier with battens above.
I would put the heating upstairs - if underfloor heating, then install and put into operation immediately and lay the screed. Temperature differences between the ground floor and the upper floor are not desirable.
Rough plumbing should of course be installed at the same time.
Just as plastering should be done right away - it is just a mess later.

Later then drywall the ceiling, lightweight walls, electrical installation, floor coverings, wallpapering/painting, interior doors, sanitary installations.