Chimneys, especially of the masonry variety, are not nearly as popular as they used to be, but if you have an older home, there are things you need to know about proper maintenance, particularly in regards to the flashing around where the chimney comes through the roof.
 
It’s an easy enough fix to reinstall improper flashing or to sure it up with a little roofing cement. Installing counter-flashing is also a common thing that is missed by some roofers. Even with these items in place, you might still have a water entry problem if you have a chimney that is more than 30 inches wide at the downhill side.
 

Why Is There A Leak At My Chimney?

 
A common thing I see missing on wide chimneys is a cricket. Cricket flashing is a miniature roof installed at the backside of chimney to divert water around it.
 
 
 
Without this simple design, the chimney acts as a dam and can hold water for a long period of time behind the chimney. That water eventually finds its way beneath the shingles, behind the flashing, and into the attic.
 
Here is an example of chimney in need of a cricket:
 

 

When is a cricket required?

 
The general rule is when a chimney is over 30″ wide, but it is possible for chimneys less than that to need one. If you are experiencing trouble with debris, puddling, or freezing water behind your chimney, a cricket may need to be installed. Hire a home inspector or a roofing contractor to inspect your chimney.
 
The process of installing a cricket is relatively simple and a good roofer will be able to do the job for you. It sure beats hiring someone to repair and replace roofing materials after a prolonged leak.
 
Check out this article from the Journal of Light Construction on how it’s done.