Cost estimation per square meter of living area for a hillside house with basement and garage

But there will only be 90m2 of living space left for 3 people. And a separate office for home office must also be included. Therefore, it will still work

I told you to go to an architect. Idea, for example, to build a staggered house on two levels. One level on top and then not with a basement, but staggered pushed out (so only slightly overlapping).
I couldn't find any examples quickly, so only the following image as an idea for the concept. You just have to imagine the idea of it staggered in your slope. On top 70sqm with a roof terrace and on the bottom pushed out maybe another 50sqm. In total your 117sqm. Should significantly simplify/make the earthworks cheaper.

No developed attic and max. 117 m2 building area. Period.

But that's not how a development plan is written or read. Period. Please show the development plan. Yes, there is a floor area ratio and yes, there is a 1 in the number of floors. But that does not mean that roofs may not be developed. The Roman 1 means a FULL floor, nothing more. Period. I'll put it this way: if you limit your options, that's your bad luck, not ours. We can only show you that much is being misinterpreted.

I would also like to see the "nicht ausgebaute Dach" in black and white sometime.

Please show the development plan.

This is what it looks like. But please, no fundamental discussions about permanent residence.

All statements we received in the course of the building inquiry excluded a roof extension.

Please, but no fundamental discussions on the topic of permanent residence.

In my opinion, there is no need for any discussion. These are weekend plots where only weekend houses are intended to be built. However, I do not read anywhere that the roof may not be converted.

The development plan is very one-sided. No developed attic and max. 117 m2 building area.

I do not see a specific floor area there, but "0.1". If that means 117 sqm, that would be 1170 sqm of plot in the taxable area (i.e. zones to be kept free from development not included).

No more and no less. We have already tried there with legal counsel to achieve a change. No chance. Nothing will happen there from the municipality and building regulatory authority.

A lawyer knowledgeable about the matter would also know about the hopelessness already from lack of authority: builders can apply for exemptions for their specific building project on their property, changes to development plans are requested by a council faction.

But please no fundamental discussions on permanent living. All statements we received in the course of the building inquiry have excluded an attic expansion.

I know such a statement only from development plans that explicitly designate holiday home building areas. Any fundamental discussion there is also absolutely pointless, see most recently in the thread (which you are not by coincidence familiar with). Are you specialized in such types of plots, or are we still talking about the same one? Sorry that I did not recognize you right away for once – because this discussion was academically a paragon of uselessness, a concrete house design does not change anything about that.

This is how it looks. [...] [pointless external link]

Why don’t you just call it self-googlable?

These are weekend plots where construction is only intended for weekend houses. However, I do not read anywhere that you are not allowed to expand the roof.

On the contrary, in that type of development plan that is even regularly included – because a simple refusal of a full floor would not be sufficient here to create effectively unwanted building volumes. They simply do not want permanent living options bulged out into every regulatory loophole – “period” (to quote the original poster).