Why is My Chimney Leaking?

Do you have a chimney leak? Are you wondering if the cause of the leak is the chimney or your roof?

Anytime you have a leak it’s stressful and frustrating. Well, some of the most frustrating leaks have to do with chimneys.

There's questions of whether it's the chimney, the roof, and who you should even call. But the truth is, there could be multiple reasons your chimney is leaking, and who you call depends on the type of leak.

For over 35 years, Bill Ragan Roofing has helped homeowners understand and fix leaks that are causing them to lose sleep. So, let's break down why your chimney could be leaking and what to do about it. 

By the end, you'll have the answers to:

• Why is your chimney leaking?

• How is each chimney leak fixed?
• Who do you call for a chimney leak?

Why is your chimney leaking?

There are multiple reasons a chimney leaks, it could even be just the chimney, the roof, or a combination of both. However, there are four issues that are more common from a roofing standpoint. 

Let's look at the following reasons why a chimney leaks:

• Brick saturation
• Flashing problems
• Lack of a roof cricket behind the chimney
• Water through a damaged top or cap

Brick saturation

If you have a brick chimney, bricks and mortar are porous enough to absorb water when it rains. In a perfect world, the chase top (top of your chimney) directs water evenly off of it in all directions.

Unfortunately, what usually happens is the water goes off one corner of the chase top, and after it's been raining for a long time. Eventually, water saturates the bricks so much that it drips inside the chimney.

That isn’t as common today, but it’s still a problem homeowners call about every time there’s a prolonged period of rain.

How to fix a chimney leak caused by brick saturation?

To fix this a chimney leak from oversaturation, you'll need to seal the bricks with a masonry water repellent that prevents water from saturating the bricks and mortar. This can be done by a roofer or a chimney company, it just depends if it's a service the roofer offers.

Flashing problems

Roof flashing is a thin metal material that roofers install to direct water away and prevent it from entering certain areas of your roof, especially your chimney. Flashing problems are the main cause of chimney leaks from a roofing perspective.

(Rusted and cracked flashing around a chimney)

This means a chimney has nothing stopping the water from getting inside if there's an issue with the flashing around it. Usually the flashing was improperly installed, but it's also possible the roofer didn't replace the metal when it should have been during the roof replacement.

Now, if the flashing was good at the time and reused, it may just reached the end of the lifespan after more years of exposure. However, a reputable roofer will always recommend replacing flashing during a roof replacement if the metal is rusted, damaged, or is near the end of it's life.

How to fix a chimney leak caused by flashing problems?

Fixing a chimney leak caused by flashing problems is fixed by simply replacing the flashing. Depending on the chimney's material, it'll be step or counter flashing. Apron flashing may also be required based on the location. 

But either way, replacing flashing can be done during a roof replacement, or retroactively on an older roof. Just know it'll be a very expensive repair if it's replaced on an existing roof. 

Lack of a roof cricket behind the chimney

A roof cricket is a double triangle structure built behind a chimney to divert water around it properly. A cricket ensures water splits down each side instead of pooling and backing up when it hits the flat wall of the chimney.

(Roof cricket on a large chimney)

This is so important that the 2018 International Residential Code, the standardized building code book, actually requires crickets on any chimney over 30 inches wide. So, if you have large chimney over 30 inches wide, it may be leaking because it doesn't have a cricket. 

Just know that it's still possible for a leak to happen without a cricket on a smaller chimney that doesn't technically need one. But if you've had chimney leaks in the past, a roofer may recommend a cricket to try to stop the problem.

How to fix a chimney leak without a cricket?

If a chimney is leaking because of pooling water, the way to fix it is by building a roof cricket. A frame will be built, then decking, ice and water shield, and the same roofing material as your roof will be installed over it. 

Like replacing flashing, building a cricket on an existing roof is very expensive. However, including it as part of a roof replacement wraps it into the full cost. 

Water through a damaged top or cap

The top of your chimney is covered by a chase top to prevent water from coming straight down into your home. It'll have a hole cut in the middle for the spark arrester and chimney pipe to come through that'll be sealed with caulk. 

If the chase is lower in the middle than the rest of the steel panel, it holds water. This leads to a leak coming through the top of your chimney because the chase top is rusted, cracked, or damage. 

This leak can also happen from the caulk failing around the hole that the chimney pipe and spark arrestor comes through. Whatever the problem is with the chase top, you can catch these potential chimney leaks with yearly roof maintenance. 

How to fix a chimney leak a rusted or damaged top?

Fixing a leak through a chase top or chimney cap requires sealing the cracks with caulk another type of sealant. However, it may need to be replaced if the rusting is widespread or the cracking is too severe. 

Who do you call to fix your chimney leak?

When it comes to chimney leaks, I recommend starting with a local roofing contractor first. Let them inspect the potential problem that could be causing the chimney leak, like flashing, lack of a cricket, or oversaturated bricks. 

If it's any of these problems, a roofing contractor should be able to take care of it. They can also seal small issues with a chase top. 

However, a chimney company will most likely have to replace a leaky chase top. To remove the spark arrestor, replace the chase top, and then put the spark arrestor back on, a company needs a rider on their insurance policy in case it doesn’t get put back together right.

Well, most roofers don't have the rider on their insurance policy. If a fire starts, the fire inspectors will look towards the last person who touched it.

Without the rider, the roofing company will have a huge problem on their hands with the insurance company. So, always call a roofer first, let them do the inspection, and then figure out the next steps to take care of your chimney leak.

How do you find a great roofer to diagnose your chimney leak?

Now, you have an idea of what could be causing your chimney leak and who to call first. Obviously, you need to trust that you'll get an accurate diagnosis. So, finding a roofer you can trust to do this is crucial. 

Unfortunately, the industry in the United States is oversaturated with companies. So, how do you find one you can trust in a sea of roofing companies for you chimney leak?  

It simply comes down to knowing what to look for when looking at potential company. That's why I wrote another article with tips every homeowner needs to find a great roofing contractor. 

Check out 9 Tips for Hiring a Great Roofing Contractor to hire a great one in your area for your chimney leak.