What Causes Chimneys to Leak?


Chimneys are designed and built to withstand constant exposure to the elements. However, even the best built chimneys can be damaged or deteriorate over time. Chimney damage often leads to chimney leaks; with so many different components, it can be difficult to determine the exact cause of a chimney leak.

Prevent Leaky Chimney - Littleton CO - MountainManCauses of chimney leaks

Diagnosing the cause of a leaky chimney can be difficult; because of this, we recommend having a chimney inspection done by a certified professional to identify the cause of the lea. Finding and repairing the source of the chimney leak first can prevent additional water from getting in after chimney repairs are made. The following are four of the most common causes of leaky chimneys.

– Chimney cap: The metal top and mesh sides of the chimney cap keep moisture, animals, and debris out of the chimney. However, if the chimney cap is improperly fitted, incorrectly installed, or damaged, water can easily flow into the top of the flue and down into the rest of the fireplace system.
– Chimney crown: The stone or masonry of the chimney crown is the slab that surrounds the flue and covers the top of the chimney structure. Because of their location, chimney crowns often bear the brunt of the chimney’s exposure to the elements; this can cause them to deteriorate faster than other chimney components. When this occurs, water can seem into cracks or holes in the chimney crown.
– Flashing: Chimney flashing creates a watertight seal on the joint between the roof and the chimney. Flashing can lose its seal due to overexposure to the elements, damage from storms, changes to the surrounding roofing materials, or improper installation. Leaks caused by flashing are often misidentified as roof leaks because the water appears on ceilings and walls instead of inside the chimney.
– Masonry: Water from rain, ice, snow, and even sprinklers can cause masonry to deteriorate over time. Damaged masonry can chip, crack, and spall because of overexposure to moisture. Not only does this let water into the chimney, but it can also affect the structural stability of the chimney structure.

How to prevent chimney leaks

While it is impossible to keep your chimney away from water, it is possible to help prevent chimney leaks. One of the easiest – and most important – ways to prevent a chimney leak is by having regular sweepings and inspections. This annual maintenance allows minor chimney problems to be identified and repaired long before they create serious damage.

In addition to regular annual maintenance, masonry can also be waterproofed in order to prevent water damage. During the waterproofing process a specially designed water repellant is applied to the masonry; this allows the bricks and mortar to retain their semi-porous nature without letting water be absorbed by the masonry. Waterproofing may also be able to stop the deterioration process on chimneys with existing water damage.

If you have a chimney leak – no matter how small – don’t wait for the leak to get worse before calling a chimney sweep. Contact Mountain Man Fireplace & Chimney today to schedule an inspection; our certified technicians can find and repair the source of your chimney leak!