Chimneys before Rumford, like this one at Williamsburg built about 1760, were built outside of the exterior wall of the house and built away from the roof mainly to reduce the risk of fire. The fireplaces were big and deep.
After Rumford, in 1796, showed how much more efficient shallow fireplaces were, the chimneys came inside of or were part of the exterior walls of the house.
Chimneys were not tacked on the outside again until the mid twentieth century after central heating was common, the science of building a good fireplace had faded and deeper inefficient modern fireplaces became "optional".
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