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The Pros Guide to a Leaky Chimney

Traditional masonry chimneys are porous, and there are multiple areas of a chimney that, when worn or damaged, can cause a leaky chimney.  Water can be very destructive to chimneys. It can cause bricks and mortar to crumble and erode. It can damage the flue liner, damper, and other internal components, which increases the risk of fire and exposure to carbon monoxide fumes. Annual chimney inspections and regular chimney cleaning can help prevent chimney leaks. The following are four common causes of a leaky chimney.

Chimney Cap

chimney cap replacement, fennimore WIA damaged or missing chimney cap is one of the most common causes of a leaky chimney. The chimney cap is on top of the chimney and covers the flue to keep out rainwater.  It also helps prevent small animals and debris from clogging the flue vent. Strong winds and heavy storms can damage the chimney cap and cause water to leak into the firebox.  Replacing a damaged chimney cap should be a priority to prevent water damage to the interior masonry.

Chimney Crown

The cement chimney crown is the top of a traditional masonry chimney that seals the flue’s edges. Its sloped design sheds water away from the chimney. However, weather conditions, extreme temperature swings, and normal wear and tear can cause small cracks to develop in the porous surface, allowing moisture to seep inside the chimney. Hairline cracks in the chimney crown are easily repaired and sealed by a professional chimney technician. However, more extensive cracking or crumbling may require a chimney crown replacement.


The flashing is a piece of sheet metal that seals the seam where the chimney and roof meet. When the chimney flashing is warped, corrodes, or rusts, moisture can seep into the chimney and cause extensive masonry damage. It can also cause water damage to the attic and roof deck. Noticing water stains on the ceiling or walls near the fireplace is often a sign of damage to the chimney flashing. Improperly installing the flashing can also cause a leaky chimney.

leaky chimney repair in richland center wiExterior Masonry

The exterior masonry is very susceptible to weather conditions. The freezing and thawing of rain-soaked bricks and mortar can accelerate its deterioration. It can cause bricks to spall or crack, flake and crumble which creates gaps in the joints. Water can seep through these gaps and cause widespread water damage to the interior masonry walls, flue liner, and other components. The cracked bricks and gaps will also continue to expand and widen. It can eventually destabilize the chimney’s structural integrity resulting in a partial or complete chimney collapse.

An annual chimney inspection can help uncover minor damage before it develops into a more extensive problem. A chimney inspection is a visual top-to-bottom assessment of the chimney, vents, and attached heating appliances, including the masonry, chimney cap, chimney crown, flashing, flue liner, and other internal components. If any damage is discovered, the technician will provide an estimate for any necessary repairs so that you can avoid more extensive damage. If you think you have a leaky chimney, contact a professional chimney technician as soon as possible.

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