Is paving a parking lot outside the building boundary allowed?

Doing it. The federal state is Niedersachsen, in case that helps further.

I will. The federal state is Lower Saxony, in case that helps further

And what does it say there? Did you check?

Why not just ask the authority? Email, attach a short picture with an explanation of the project, and wait for a response. It works great here in our town (near Hannover).

I'm just wondering how a paved area outside the building window (3m distance to public spaces) could be prohibited... Somehow you have to get onto the property, which in most cases requires a paved area up to the property line. And if you then park a vehicle on this paved area, who is supposed to forbid you?

Am I allowed to pave a parking space outside the building boundary? According to the development plan, a building boundary is defined. Am I allowed to exceed this with paving (no roofing)? The floor area ratio is being adhered to.

How about simply not worrying too much and using grass pavers / grass grid stones? You can park on them, it's not a (completely) sealed surface and it also looks good or can be integrated into the front garden design (lawn with a few stones in it).

Caution is advised with grass grid stones... according to our development plan, these are also considered sealed surfaces...