Are you seeing water stains near your fireplace or on the ceiling by your chimney, but have no idea where the leak is actually coming from? Worried that what looks like a small leak might actually be causing mold, rot, or structural damage inside your home?
We know how stressful it is to spot a leak and not know whether it's coming from the chimney, the flashing, or the roof, and in Seattle’s constant rain, small issues can turn into expensive repairs fast.
At RoofSmart, we repair 5 chimneys a week. This includes redoing the flashing, building a chimney chase, and replacing the chimney cap. Our thorough inspection process helps us accurately find the cause of your chimney leak so that we can recommend the right repair.
In this article, we’ll walk you through the most common signs that your brick chimney is leaking, how to inspect it for leaks, and how to tell whether it’s your chimney or your roof causing the problem so you can act before serious damage sets in.
What are the signs that my brick chimney is leaking on my Seattle home?
If you’re seeing drip marks in your chimney (specifically in the firebox), that is a sign that your chimney is leaking. If you’re noticing water stains on your ceiling around the chimney, that can be caused by a leak in the chimney or in the roof.
If your chimney looks old and worn out, or is growing moss, this is also a sign that it might be leaking. Here’s an example:
This chimney was poorly installed, and has worn out and begun leaking over time.
Just like with any leak on or around your roof, it’s a good idea to inspect the area that you suspect is leaking right away and call out a professional to help you identify and fix the leak as soon as possible.
If you suspect that your brick chimney is leaking, it’s a good idea to start at the top and work your way down. Here are the areas on your chimney that you should inspect and the signs that it’s leaking:
1. Chimney crown
The chimney crown (or chimney cap) is what covers the top of the chimney. It can be made out of various materials, but it’s usually metal or stone. This is what a good chimney cap should look like.
If the chimney crown is cracked or has holes, this is a sign that it’s leaking. Water might be dripping down the shaft to the firebox.
If the crown is made of stone, it can get saturated with a lot of water, which causes cracks to form.
Here’s an example:
2. Flues
Chimney flues are the vents that run all the way through the chimney and stick up through the crown. The heat in the flues will cook the air a little bit, and it'll evaporate the moisture back up and out.
If you don’t use your chimney for a while, moisture can build up inside the flues and cause mold to grow. However, you cannot see this because it’s inside the chimney. You’d have to remove the covers.
3. Where the crown and the brick facade meet
At the bottom edge of the crown where it meets the brick, there’s supposed to be mortar filling the gap. This mortar is usually cracked.
If the mortar is cracked, then this is a likely leak point. Water will drain off the edge of the crown right into that crack, and then it's inside the chimney. This is an insidious leak point because it's coming down right next to the outer wall, so it's hard to tell what’s going on.
4. Bricks and mortar
There could be cracks or holes anywhere along the rest of the chimney. Any of the bricks or mortar could have cracked or degraded enough to let water in. Sometimes there’s an obvious crack; other times it’s very hard to see.
Here’s an example:
If the bricks are flaking, that doesn’t mean there’s a leak, but it is an indication that it's going to be a leak soon because it's crumbling.
5. Flashing
Every chimney has flashing around the base where it comes out through the roof. This is to protect it from leaks. But if your contractor did a poor job of installing the flashing (like in the picture above), water can enter at the base of the chimney and seep into the roof.
This can cause mold or rotting wood in your attic.
A lot of chimneys have a cricket built on one end to help redirect water flow and prevent leaks. They look like this:
But if they are installed poorly, they can leak and start rotting underneath. Here’s what this cricket looked like underneath before we fixed it:
Check out this graphic for more information on crickets:
How do I know it’s not a roof leak?
A leak around the flashing at the base of your chimney is considered a roof leak.
All the other places that can leak would be considered part of the chimney, not the roof. Chimney leaks can appear in the firebox or within the chimney, but sometimes they show up in your roof.
If you’re not sure what’s causing the leak, you can have a roofer come out and wrap it in plastic. If the leak stops, it’s the chimney. If not, it’s the roof. We’ve done this test many times to help us identify the leak point.
What causes a brick chimney to leak?
The two main causes of leaking chimneys are poor installation and degradation (which eventually leads to cracks).
In a rainy area like Seattle, any vulnerability in your roof is at risk of developing a leak, which will lead to costly water damage. Unfortunately, water saturation can cause degradation, which leads to leaks even faster.
One of the challenging things is that a chimney can have like six things wrong at once. It may not be just one thing. This makes it hard to figure out what the actual cause of the leak is.
How Much Does It Cost to Repair a Leaking Chimney or Roof in Seattle?
By now, you understand the many ways a brick chimney can leak—whether it’s from cracked mortar, a failing crown, damaged flashing, or even something hidden deep inside the chimney itself. And as you’ve seen, those leaks can cause serious problems like mold, wood rot, and structural damage if left unchecked.
If you’ve identified signs of a leak or even just suspect one, the next step is figuring out what it will take to fix it and how much it’s likely to cost.
Your next step is to read our article “Roof Leak in Seattle? Here’s What It Will Really Cost to Fix It” to learn the key factors that affect leak repair pricing. That way, you know what to expect before picking up the phone.
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