A chimney cricket is a roof-like structure that is built onto the backside of your chimney. As seen in the image above. Chimney crickets are used on large-sized chimneys or chimneys that are in abnormal spots on your roof that may block the flow of runoff water. A chimney flashing is then installed that diverts not only runoff water but also any leaves and debris off the sides of the chimney.
How wide does a chimney have to be before it should have a cricket? 24 inches to 30 inches depending on the location and the roof structure surrounding your chimney.
Chimney crickets are also known as chimney saddles and chimney diverters.