[Cob] Are roof overhangs absolutely necessary?

[Christopher Reinhart]

Anytime there is a change in materials on a structure, like between the
walls and the roof, there is an opportunity for the elements to penetrate.
With no overhangs, this joint is very vulnerable. Even a short overhang of
six inches will go a long way to protect this joint.

Also, in a gabled roof, there is an appreciable difference in what is
happening on the gable-end walls and the shorter side walls. Nearly all of
the rain and snow is shed off over the side walls. Without an overhang, this
precipitation is potentially running right down the side of the building. A
gutter is an option, but I would highly recommended against placing a gutter
on a roof with no overhangs. Gutters inevitably clog, causing water to
overflow. Without an overhang, the water that overflows the gutter can
easily flow back into the wall. This is not just speculation, but what I
have seen in making roof repairs on numerous conventional buildings.

With the main enemy of cob buildings being water, I would recommend
at-minimum having a short overhang on both the sidewalls and the gable-end
walls.

-Christopher Reinhart