So I understand correctly that 9m per side are permissible, so a FG with 9x6m in the corner of the property (one side 9m, the other side 6m boundary development) is allowed? That fits...
So I understand it correctly that 9m per side are allowed, so an FG with 9x6m in the corner of the property (one side 9m, the other side 6m boundary construction) is allowed? That fits...
No, that is not what is meant by that. 9 meters of permitted boundary construction applies in total. In a corner, it would be 15 meters.
Quotation Lower Saxony Building Code 2012, §5 (8) sentence 2:
2 Without distance or with a distance reduced to 1 m from the boundary are permitted
1. Garages and buildings without rooms for occupancy and fireplaces with a height of up to 3 m [...]
3 Structural installations according to sentence 2 may underrun the distance according to paragraph 2 on a total length of 9 m per property boundary, but on a building plot overall only on a length of 15 m.
As far as I know, this is regulated similarly in most federal states, but there are also specific deviations regarding this topic in each state building code. For example, different provisions can be formulated in the development plan.