House extension - beginner questions

You might also consider going to the building authority in person to find out whether your project is generally approvable or outright hopeless. The technical feasibility should probably be checked by your architect or the structural engineer.

Thanks ypg...

I was not aware of that.
In my layman's understanding, I thought every floor was considered as such...

Then I will ask the municipality what they actually "allow".

If I get a positive response, the next step would be to find a suitable architect.

Thought in my layman's understanding that each floor is also considered as such...

Floors do not exist in building law terminology.
It is always about full stories.
Each federal state also has its own regulation on this.
Just google Hessen full story.