Why does my Chimney Leak when it rains?
Maybe you just noticed a leak in your chimney for the first time or your chimney seems to leak every time it rains. Either way, a leaking chimney could signal greater problems that require immediate professional attention.
Left unaddressed, a chimney leak can cause damage and potential structural problems with the chimney and the home. Let’s explore some of the most common causes of chimney leaks and how to repair/prevent them.
Reason #1: Flashing
The most common place a chimney leaks is from the chimney flashing. Flashing is found where the roof meets the chimney. The flashing is meant to provide a waterproof seal. As a result, compromised or deteriorated flashing provides an opportunity for leaks.
The number one sign that your flashing is the cause of your leak is water stains on the ceiling of the top floor around the chimney. If you notice a leak in this area, the flashing may need to be resealed or replaced.
Reason #2 Oversaturation
Another common reason for Chimney leaks is oversaturation. Masonry is water-resistant but not waterproof. It will absorb water and the water absorbed evaporates off. 5lbs. of masonry can absorb up to ½ cup of water. After it reaches this level, a saturation leak can occur even without any visible holes or damage. Saturation leaks can often go undetected by homeowners until obvious problems arise.
To remedy or prevent oversaturation, a semi-permeable waterproof sealant can be applied to the masonry surfaces. A semi-permeable barrier will provide additional water-resistant protection to your chimney while allowing trapped moisture to evaporate off.
Non-permeable sealants should not be used because they can trap moisture inside. If the paint begins to break down in one area and let water in, there is no way for the water to get out and oversaturation will occur.
Reason #3 Chase Covers
Most homes built in the last 30 years were built with Factory Built Fireplaces. These fireplaces were installed with galvanized steel chase covers. Galvanized steel rusts and breakdown over time. When the chase cover breaks down it will let rain enter the top of the Chimney.
The solution is to replace the old, galvanized steel Chase Cover with a Stainless-Steel chase cover.
At The Chimney Scientists, we specialize in diagnosing and repairing chimney leaks and waterproofing chimneys for leak prevention. If you are facing a leak or are just concerned about the potential of a leak, contact us and schedule a time for an inspection.