What are the rules regarding property boundaries on the roof? Can the property boundary deviate because of the chimney?

Questioner

We are in a discussion with our neighbor regarding the property boundary on the roof. An incorrect dormer window was built by previous owners and must be converted into a permit-free dormer window. To do this, there must be at least 50cm of space to the boundary line of the neighbours' house. The municipality has indicated that this must be 50cm to the roof surface (centre line of the dividing wall). We now want to adjust the dormer window in accordance with these rules. However, there is also a chimney on the roof. However, this is not completely in the middle and according to the neighbor is jointly owned. He thinks that the middle of the chimney should be taken as the starting point for the 50 cm and therefore not 50 cm to the dividing wall. Is he right about this? Could it be that the property boundary on the roof is not straight?

Lawyer

Yes, in principle, the neighbor is right. A property boundary can run through the middle of a chimney.