A chimney cricket is a roof like structure that is built on the backside of your chimney. As seen in the image on the right. Chimney crickets are used on large sized chimneys or chimneys that are in abnormal spots on the roof that may block the flow of runoff water. A chimney flashing is than 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 diverter.