Soldered copper flashing for a rooftop watershed.
Synopsis: A chimney cricket is a mini-roof that helps shed water away from the vulnerable intersection of a sloping roof runs and the back of a chimney. In this article, the author shows how to make a soldered copper cap for a cricket.
The best place for a chimney to exit a roof is at the ridge. Water will run away from the chimney, not toward it, and flashing becomes a fairly simple matter. Builders in New England did this back in the days before sheet metal was readily available.
When you move a chimney downslope, however, runoff will strike it, often forcing water up under the flashing and down into the house along the bricks. Leaves and other debris can build up behind the chimney and decompose into a moisture-laden compost that rots roof boards and corrodes the flashing. The way to avoid this mess is to build a well-flashed cricket.
A cricket, or saddle, is a miniature gable roof covered with metal that sits between the back of the chimney and the main roof. The intersection of cricket and main roof produces a pair of valleys that divert water, snow, and debris around the chimney. Recently I built a small cricket for a wooden chimney structure that houses a pair of woodstove chimney pipes. Although the wooden chimney structure made attaching the cricket easier, constructing the cricket and flashing it were much the same as they would be for a masonry chimney.
The cricket I built was small enough to make with plywood—no rafters—but I’ll speak in terms of common and valley rafters in order to relate the geometry to standard roof framing. Since the chimney structure was 2-ft. wide across the back, the run of the cricket common rafter was half of that (12 in.). The…