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Leaky Chimney Causes & Fixes!



There is nothing more annoying than a water leak in your house. One of the potential sources of a water leak is the chimney. There are many causes for what may cause your chimney to leak. While the following may not be an all inclusive how to repair your chimney, we will touch upon the most common causes and effective ways to eliminate them as a source of your water issues.


Let's first get acquainted with the anatomy of a chimney and then dive into the three most common causes for a leaky chimney.




Cause #1: Leaking through the Bricks or mortar joints


Bricks and mortar are porous and may be absorbing too much water.

Older bricks and even newer brick are porous. Usually this is not a problem as it takes a fair amount of water to pass through the bricks. Unfortunately, sometimes when it rains, it pours and keeps pouring.

Or perhaps you live by the ocean or in an area with predominate wind that drive the rain into the chimney. The bricks and mortar joints will become inundated with water and may leak.



Sealing your chimney is a proven way to help minimize this. We stock Siloxane PD, a breathable water-based sealer. The important part of this is that the sealer is breathable, which means it allows any trapped water vapor to escape. Being water based, the sealer soaks into the bricks a little deeper, so its best to apply when the bricks are completely dry. The sealer may be sprayed or rolled on. Depending on the porosity of the brick and mortar, multiple coats may be needed. It is important to keep in mind that sealers do not bridge gaps, so if the mortar joints or crown is showing cracks or age, it is best to repair those first.

Sealers may need to be re-applied periodically to ensure its effectiveness.




Cause #2: Cracked or broken crown. Cracked, separated or worn-out mortar joints.


On the very top of the chimney there is a crown, sometimes called a wash, that protects the top of the chimney. Typically made of a sand & cement mixture, the crown is a potential source of water infiltration as it ages and potentially cracks.

Mortar joints age as well, and may crack or become powdery over time. Mortar joints may also separate from the brick over time, causing hair-line cracks along the bedding joints.