Try searching on Google for "Hinweise zu §§6 und 73 Bauordnung NRW". There it states in the note regarding paragraph 11.1.1 that the privilege for the entire building ceases if even a part is used differently. Then follows a clear sentence on the topic: >>This also applies if the roof area of the building is used as an open seating area.<<
Yes, that is what I deal with professionally every day.
You have to read that differently in this context, because it refers to a (partial) use of the roof area that is located outside (!), as you will additionally find in the NRW explanations, for example:
For buildings that are partially located outside the clearance area (e.g. a double garage in the side boundary setback of the main building), this also applies to the part located outside the clearance area.
In plain language, this means that a boundary garage 3m wide, which for example is only used as an open seating area for 1m, loses its entire privilege. This results in not only a 1m deep easement burden on the neighboring property but a 3m deep easement.
As long as you stay within, meaning the open seating area has a 3m boundary setback, this regulation does not apply. Instead of the open seating area with a 3m boundary setback, you could also build an enclosed living space without it needing to be secured by an easement or affecting the privilege of the boundary garage.
If it were otherwise, I would have to be seriously mistaken.
The trick with the balcony without contact above the boundary garage instead of an open seating area on the garage also precisely solves this problem: if you build a terrace door as access on the garage with, for example, 1m paving, the privilege of the entire garage is gone. If you build the balcony on the house without contact to the garage below, the balcony can protrude 1.50m from the house wall. This is somewhat paradoxical but correct.
The distance in NRW should generally be oriented to the height H of the (residential) building, then the factor, depending on the location, i.e. 0.8; 0.5 or 0.25 H.
0.25 applies, to my knowledge, only in commercial areas, but the value can be reached with narrow side privilege, which may now be applied on all sides in NRW, even in 0.5 areas. However, this leads relatively quickly to almost absurd building heights because with a 1m parapet height, the upper edge of the floor where the balcony is attached could be at 11m (3.0m / 0.25 = 12m). This corresponds at a floor height of 2.90m to at least the second upper floor, at 2.75m already the third upper floor, which almost necessarily results in a 4-story, rather 5-story building or a cantilevering roof terrace of a 3- to 4-story building with at least 14m total height. In other words: this rules out normal residential areas, may only occur in extreme hillside locations and small plots and/or in inner-city areas.
With the 3m, you already get quite far in practice; only when the building body becomes longer than 16m does the narrow side privilege fall away for the part of the building that exceeds the 16m, and then the building body must retreat more than 3m in this area. But those are really massive structures – whoever places this privately for sole use can also afford 1m more plot.
Even in 0.8/0.4 areas there is still enough leeway; 3m is easily sufficient for 1-2 family houses.
Best regards
Dirk Grafe