The Misunderstood Chimney Cricket

At first thought, the mention of a chimney cricket might bring up memories of what your grandparents may have said about a chirping insect in the fireplace – that it is lucky to have a cricket in the house, and especially near the chimney. This long-held tradition that comes from England during pre-colonial times still remains with us today. Some people even purchase brass reproductions of the lucky chimney cricket and place one or two on the hearth.

Another, and more important chimney cricket, is the one that is built on the upper back side of a chimney. This cricket sheds rain water away from the chimney rather than allowing it to beat down onto the side of the chimney that is the most susceptible to water penetration. 

This area is the least noticeable from the ground, yet likely has more damage than other sections of a masonry or prefabricated chimney.

According to the NFPA 211 Standards and International Residential Code a cricket must be built to certain specifications on the high side of the chimney next to the roof if it is 30” or more in width. When a cricket is built properly it will shed water away from the chimney and down the sides of the roof rather than seeping between flashing and into an attic or ceiling area.

The telltale signs that water is getting in where it shouldn’t are water stains on the ceiling or walls, or rafters next to a chimney, and/or damaged mortar and bricks or rotted wood on the exterior chimney on the high side.

Springtime is the time of year when people notice this due to the frequent spring rains that occur each year. A driving rainstorm will usually result in water leakage if the exterior chimney is not properly secured against the elements.

Your local professional chimney sweep should examine the cricket (or lack of one) when he or she inspects the chimney during routine maintenance. He will look for the proper sizing of the cricket and proper installation of J and counter flashing, which work together to keep damaging rain water out of the house. If there is no cricket or there are problems with it the sweep will do the repairs or recommend someone who is experienced with roofing and building crickets. Roofers normally build the cricket at the time of roof construction.

Cricket dimensions per IRC code requirements are as follows:

 


Roof slope

Height of cricket

Divide by

Or multiply by

12-12

1/2 of chimney width

2

.50

8-12

1/3 of chimney width

3

.33

6-12

1/4 of chimney width

4

.25

4-12

1/6 of chimney width

6

.06

3-12

1/8 of chimney width

8

.125

 

However, even chimneys less than 30” wide may need a cricket if water penetrates the flashing and gets inside the home.

Ask your chimney sweep to do a leak test (or do one yourself), which will involve spraying the chimney down heavily with water from a hose then looking for signs of leaking in the attic, walls and ceiling next to the chimney.

If water appears, there is a problem that needs to be addressed before damage occurs to ceilings, studs, rafters, and walls. 

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