Bonnet Roof

A bonnet roof (sometimes called a kicked-eave roof) has two pitches on each side, like a mansard or gambrel, but reversed: the upper slope is steep and the lower slope, near the eaves, is shallower and projects outward. The lower slope often extends over a porch or veranda, giving the building a wide, sheltering brim that resembles a bonnet.

Where it is found

Bonnet roofs appear on traditional barns in the western United States, for example in Grand Teton National Park in Wyoming, where the shallow lower slope shelters the walls and stored equipment. Related "kicked" or flared eaves, in which the bottom of the roof flattens out over the wall, occur in many traditions worldwide. Terminology varies, and many of these are described simply as flared or bell-cast eaves.

Construction

The change of slope is usually created in one of two ways:

• Sprockets: short tapered timbers fixed to the lower ends of the rafters to lift and flatten the eaves (the British term sprocketed eaves).
• Separate rafters: a lower set of rafters at a shallower pitch, often running from the wall to porch posts.

Advantages and drawbacks

• Sheds water well clear of the walls and provides shade and shelter.
• The shallower lower slope reduces the speed of water at the eaves, but it must still meet the minimum pitch of the chosen covering; very shallow kicks may need extra underlayment or a covering rated for low slopes.
• The break in slope needs careful flashing, and snow can accumulate at the transition.