When installing asphalt shingle roof systems, contractors often encounter brick masonry chimneys. If not properly detailed, water may leak where a chimney intersects a roof system's plane. One common method to avoid such a problem is to install a cricket.
A cricket is a relatively small roof area constructed to divert water from a horizontal intersection of a roof and chimney. NRCA recommends crickets be installed at the upslope side of chimneys when a large volume of water, snow, ice or debris is expected; the chimney is more than 24 inches wide; or the roof slope is 6-in-12 (27 degrees) or greater.
Crickets typically are constructed from metal. The metal type and thickness used for cricket flashings should be commensurate with the anticipated service life of the asphalt shingle roof system. NRCA suggests cricket flashings for an asphalt shingle roof system be fabricated from one of the following metal types and thicknesses: