If you haven’t noticed we’ve been getting a lot of rain lately. If your roof is in good condition, you’re taking it with a grain of salt. However, if you have a leaky chimney, heavy rains aren’t exactly good news. Over time a leaky chimney can cause your chimney damper to rust, the firebox to deteriorate, the adjacent walls to rot, water stained walls and ceiling and eventually the chimney will tilt and collapse.
Chimney crowns are the least expensive method of keeping rain, snow, and water out of the chimney. They are an important component of the heating system since they cover the chimney flues or openings preventing water and wildlife (birds, raccoons etc…) and debris (branches, leaves etc…) from entering the chimney. Caps also act as a spark arrestor, preventing sparks from leaving the chimney and landing nearby.
There are many reasons for a chimney to leak including the chimney flashing (the metal that joins the chimney and the roof) but most of the time the chimney leak can be traced back to a cracked chimney cap. When left unprotected, a chimney crown will eventually crack and deteriorate.
The main reason that a mortar chimney cap cracks is due to the freeze and thaw process. We light our fireplaces and wood stoves in the winter. When the temperatures drop below freezing, water that accumulates on the chimney crown will expand and contract causing it to crack. Water will eventually make its way down the chimney and into your home.
The first question that we get from our customers is should we repair or replace? Before we can answer that we’ll have to perform an inspection. If the crown was properly constructed and their isn’t extensive damage then repairing it the more cost effective alternative. A well-built chimney crown should be downward sloped so that it directs the water from the flue to the edge of the crown. An adequate drip edge should direct the water away from the crown and the chimney so that it doesn’t accumulate on the surface. Unfortunately most masonry chimneys are built with an inadequate crown constructed from an ordinary mortar mix (not the recommended Portland Cement base and include the ingredients silica sand, limestone, and clay) that is designed for years of weather abuse without cracking, chipping or deteriorating. The overhang and the flue liner tile on all sides of the chimney should be greater than two inches.
There are a few options for dealing with a cracked chimney crown. The crown could be repaired. But in some cases it’s beyond repair and will have to be totally replaced. The best way to perform a chimney crown repair is with an elastomeric product that will prevent water infiltration and remain flexible over time.
There are several great products available such as ChimneySaver and Chimney RX. It’s important that a thorough chimney inspection be performed before and after to ensure that the chimney doesn’t leak.