hi. thanks for going on adding information in the area. 
about buildings… I generally tend not to join them reusing nodes: I've observed that there's always a gap between the roofs of adjacent buildings in urban areas like this. 
also, I'm afraid that we should really be mapping the footprint of the *building*, not of the *roof*. that's a whole challenge for our area! my approach is to just slightly underestimate the building.