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The architects Bevan & Liberatos created this beautiful plan of a working barn on the coast of South Carolina, based on a water color from 1799. The big technical improvement can be found on the eaves, which are now bellcast eaves, or sprocketed eaves, perfectly adapted to SC. 
Buildings in South Carolina need steep roofs to resist hurricane force winds, but at the same time they need bellcast eaves to throw the rain water as far as possible from the walls themselves, especially to prevent splashing from damaging the lower parts of the building.
A building in Croatia (where snow rather than hurricanes is the problem that determines the roof shape) that has ordinary eaves show just how badly protected the walls are from splashback. This can be solved by extending the eaves, adding sprockets, or making the wall stronger.
A professor in Japan created this to show how much water hits the wall depending on how large your eaves are. Of course, modernist buildings have flat roofs and no eaves and thus the walls will receive ALL of the rain that hits roof and walls.
But what to do if you have no material to build eaves, and you live in a place with strong winds and massive amounts of rain? The people in the Scottish Hebrides solved this by folding the roof inside a double stone wall, letting the water percolate through the wall. Perfect.
The walls used no mortar and the space between them would be filled with sand. The thatched roofs (very wind resistant to begin with) were made stronger by being weighted down with field stones and ropes.
As you can see on the diagram, there was a level piece of prime real estate on top of those walls, called tobhta, where people could sit and work during sunny days or ducks could graze on the grass. Here is Kate MacDonald of Balephuil standing on the tobhta of her house.
But lets return to eaves. The bellcast eaves were constructed with a sprocket, which in in German was called ausshifter, and in French a coyau. We still build them today, just like we did in the middle ages.
Eaves are a universal adaptation to roofs in most cultures. The native Yurok people of northern California built these peculiar plank houses (worthy of a separate thread) with three part roofs and good eaves. The center part could be adapted, opened, to suit the weather or time.
It is tricky to build eaves that are good enough to protect a two story house, and expensive, so in those cases it is more convenient to build a separate set of eaves on the most exposed sides of a building, like on the 1725 John Chad House in Pennsylvania.
Eaves are a sacrificial part of a house, they take the brunt of damage but are easily repaired in traditional architecture, not so much in modern building. The eaves on the Hans Herr House in Lancaster PA, from 1719, can be fixed with a hammer, some 25 cent shingles and a ladder.
Incidentally these stone walls are also easy to maintain if done regularly. A six year old with a butterknife and a small bucket of mortar can do it. Here is a beautiful house in Betlehem, Pennsylvania.
