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Why is Water Coming Through My Chimney?

Water entering your chimney isn’t just messy; it can cause significant damage leading to poor chimney performance and other issues. This article looks at why water enters the chimney, what kind of damage it can cause, and what you can do to protect yourself.

Leaking Chimney Repair Trenton, NJWhy Does My Chimney Leak?

During heavy rain and snow, it’s easy to see how water can fall straight down into an unprotected chimney, but that’s not the only cause of water leaks. Masonry materials are highly porous, meaning they absorb water. Because your chimney is exposed to the elements year-round, they’re at risk from water damage.

When water gets into the bricks and mortar joints and freezes in winter, it expands, creating tiny cracks that allow more water to enter. Over time, these cracks grow larger through continuous freezing and thawing cycles. If this cycle goes on for too long, you can end up with spalling bricks and loose mortar joints, and more significant water leaks.

How Water Damages a Chimney

As mentioned, water freezing and thawing form cracks in the masonry materials, leading to water leaks. However, leaks aren’t the only problem you have to worry about regarding excess moisture, such as:


Untreated water damage caused by freezing and thawing can lead to a problem called spalling, which happens when the surface of the bricks breaks off. Spalling isn’t only visually unappealing; it weakens the chimney’s structural integrity. You can spot this problem early by looking for small pieces of brickwork around the base of the chimney.


When water seeps into the chimney, either from the flue or through the brickwork, it can cause metal components like your firebox and your flue liner to rust. Or, if you have a tile flue liner, excess moisture damages it the same way it does your brickwork.

Mortar Deterioration

Repeated exposure to rain and snow also causes the mortar joints to loosen and deteriorate, weakening the overall structure. If this goes unchecked, you could end up with a chimney collapse on your hands.

How To Protect Your Chimney

According to the Chimney Safety Institute of America, water is the number one cause of chimney damage, which is why you must do everything possible to protect it. And here are the best defenses to consider.

Chimney Caps

Installing a chimney cap is the least expensive thing you can do to defend your chimney against water damage. However, there are other advantages to installing a chimney cap, such as protection against critter invasion, maintaining a healthy draft, and preventing sparks from exiting the chimney. There are various chimney caps to choose from, including stainless steel, copper, and galvanized metal. You can also install a cap with additional features such as a top-sealing damper or spark arrestor. Ask your local chimney repair service which one is best for your needs.


Flashing is material roofing contractors install on areas where the roof abuts the chimney to keep water from getting in. However, the flashing must be installed correctly for this to work, and this isn’t always the case. You can see signs of improperly installed flashing by water damage or mold growing in your attic or ceiling and by visible damage. If you don’t think your roof flashing has been installed correctly, call a professional chimney service for an inspection as soon as possible.


Another cost-effective way to protect your chimney from water damage is to get it waterproofed by a certified chimney service. Waterproofing protects against water damage, reduces the chance of needing significant repairs, and extends your chimney’s lifespan. Today’s waterproofing materials are 100% vapor permeable, allowing your chimney to breathe while still protecting it from water absorption.

Annual Chimney Maintenance Lawrenceville, NJAnnual Inspection & Maintenance

Finally, the best way to protect your chimney is to schedule annual inspections, cleaning, and maintenance by certified professionals. Annual maintenance keeps your chimney in good working order and allows you to locate and repair minor issues before they escalate and cause significant damage.

About Us

Mercer County Chimney Services is a full-service local chimney company serving Hamilton, NJ, and Mercer County residents. We’re certified by the Chimney Safety Institute of America and the National Fireplace Institute. Call us today to schedule chimney cleaning and inspection at 609-802-5288 or fill out our online form.