Are you seeing mysterious water stains near your fireplace or in your attic and wondering if your chimney is to blame? Have you been told your chimney chase is “fine,” but still have a nagging feeling that something might be leaking and causing hidden damage?
We understand how frustrating and stressful it is to suspect a leak, especially when you can’t see exactly where it’s coming from. And in a rainy climate like Seattle, the damage can build up before you even realize it’s happening.
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 what a chimney chase is, the most common signs of a leak, what causes those leaks, and what to do if you spot one so you can take action before things get worse.
How is a chimney chase different than a regular brick chimney?
A chimney chase is the wood box built around the chimney for gas appliances. Wood and siding are used for the chimney chase instead of brick because that makes it cheaper and easier to build.
This is what they look like:
And this is what a regular brick chimney casing looks like:
A chimney chase can be added if you have a fireplace insert, but your house didn’t originally include a brick chimney.
Typically, you’ll have a B vent (or equivalent stainless steel pipe) running up through the house or on the outside of the house. The part that sticks up over the roof is covered by the chimney chase.
Here’s what it looks like as it’s being built:
You don't have to worry about a fire inside because it's contained within that stainless steel pipe. There’s not that much heat in there. And a gas appliance is more efficient than a fire.
What are the signs that my chimney chase is leaking?
If done right, your chimney chase should keep water out and protect your roof for years. However, an inexperienced contractor can make mistakes that cause your chimney chase to leak.
If you suspect your chimney chase is leaking, here’s where you should look and what to look for:
1. Leak down on the bottom edge
A common place for the chimney chase to leak is on the bottom edge, where the water is more likely to run down and gather. As you can see from the picture, this can cause pretty significant rot in the wood sheathing that sits beneath your shingles.
2. Cap Leak
Sometimes, the cap of the chimney leaks. Typically, this can happen at the joint where the pipe sticks out of the chimney cap.
If it has sealant around it, then it’s possible that it will leak because sealant can fail. Welding makes it stronger. But if there is a leak at this joint, then the water can fall all the way down to your furnace. The leak won’t show in your roof.
3. Rotting Corner Trim
The corners of your chimney chase can potentially be vulnerable to leaks if they weren’t installed properly.
If they look like they’re rotten, splitting, or leaking, then the corner trim could be the cause of your chimney leak.
This is how it looks on the inside:
4. Gap, Hole, or Crack in the Siding
Another issue to check for is a gap, hole, or crack in the siding of the chimney chase. This can happen if the siding is hit by something (like a branch flying around in a windstorm) or if there was a flaw in the wood that your contractor didn’t notice during installation.
In this case, the problem was poor installation. The contractor did not include any flashing to keep water out along the slope of the roof, resulting in a leak.
5. Poorly Installed Flashing
Not only does this flashing look terrible, but it also does a poor job of protecting the roof because of how many little gaps and entry points for water it has.
If no other parts of the chimney are leaking, then the flashing might be the problem. If so, you’d notice rotting wood or mold in the attic.
However, flashing is usually not the problem with a chimney chase. If it is, then the water usually leaks through at the upper part of the chimney base, where water first hits it.
What happens if a chimney leak is left untreated?
Sometimes chimney leaks can be hard to identify, so it takes a while to notice that there is even an issue. In a rainy area like Seattle, leaks often lead to problems like:
- Mold
- Mildew
- Rotting wood
- Structural damage
All of these issues can happen in the time it takes to identify the chimney leak, so it’s important that you take action to fix the leak right away. Otherwise, these issues will continue to get worse, making your leak even more expensive and difficult to fix.
How do I fix a leaking chimney chase?
The simple answer here is replacing the cracked or rotting piece (like siding, corner trim, or flashing) that is causing the leak. But by the time you notice it, the damage is likely more than “skin deep.”
You might also need to replace the plywood around the base of the chimney if the leak has spread there and caused it to rot.
A lot of chimneys in the Seattle area sit in people’s homes without being used. If this applies to you, then it means that finding a leak in your chimney is a good excuse to seal it up or get rid of it.
You can even hire a contractor to take the chimney down to the roof deck height and then roof it over. This costs about the same as fixing the flashing. You remove the chimney down to the basement level and turn that roof opening into a skylight (which we’ve done before).
Here are some photos of the process:
And here’s the before and after shot:
Taking the chimney down to roof height (or getting rid of it completely) is a good option for you if you’re done using the chimney and are concerned it’s becoming a liability.
How Much Does It Cost to Repair a Chimney or Roof Leak in Seattle?
You now know what a chimney chase is, how it’s different from a brick chimney, and the most common signs that it’s leaking, from rotting trim and cracked siding to mold and other attic damage. The longer these signs go unaddressed, the more expensive the repair becomes, especially in Seattle’s constant rain.
If you’ve found evidence of a leak, the next question is: how much will it cost to fix?
Your next step is to read our article “Roof Leak in Seattle? Here’s What It Will Really Cost to Fix It” to learn what factors impact the cost of leak repairs, whether it’s flashing, plywood, or a full chimney tear-down, and help you understand what to expect before hiring a contractor.
Topics:
