Speaking more to residential and commercial building practices of the period,
not much consideration was given to flashing like it is today. I do a LOT of historical
work, and am often faced with the dilemma of installing a practical flashing, where
none was ever present, creating a very different appearance where a roofline will
intersect a vertical wall surface. Code calls for a 1.5" gap from siding surfaces to
bare roof sheathing. This is quite a shadow line that historically was just where the
siding and roof shingles met.
In the case of flues and stove pipe, one must suspend the hot pipe from nearby
materials that might catch fire. Code today is 18" of clearance. Back then, there
was no code. It was just built to a distance that common sense dictated. No one
wanted a fire.
"Duty above all else except Honor"