Classically - After drawing a building you have to draw the sidewalk's edge. Point no. 3 is only a probable end of the sidewalk's edge. The sidewalk's edge may run closer to the street but you can not see it without an additional measurement. It would be good to "get" to point no.3 and "go down" to the sidewalk's height not changing X and Y.
Applying FLAT - The drawn roof contour is placed on the sidewalk's edge height so the decision whether point no.3 is on the building's edge or if it's moved is immediate. There is no need of additional measurements.
Classically - Point no.5 is not a problem itself, however, there is still the question what to do once point no.8 is drawn. Can you draw directly to point no.9?
Applying FLAT - After drawing point no.8 and "geting down" to the lower roof's level everything is clear and obvious, first you should draw point no.9 and then no.10.
See:
FLAT