Do you have a chimney leak? Or are you about to get a new roof and want to know what goes around a chimney to prevent leaks?
There are a lot of roof areas that are prone to leaks, and your chimney is one of the biggest potential problems. It's a huge penetration coming through your roof, so it needs something around it to stop the water from seeping through the cracks.
But what exactly goes around chimneys to prevent leaks?
For over 35 years, Bill Ragan Roofing take pride in helping you and other homeowners understand their roof, even the chimney. That’s why we’re going to cover the roofing material contractors use to prevent water from getting into your home through the chimney.
By the end of this article, you'll learn the answers:
- What's placed around a chimney to prevent leaks?
- What actually causes a chimney leak?
What's placed around a chimney to prevent leaks?
With a penetration as large as a chimney, leaks are always a huge concern. While doing things the right way goes a long to preventing leaks, the physical materials installed around a chimney are what actually stops the water.
The materials that actually go around a chimney to prevent leaks are roof flashing and a cricket.
Roof flashing
Roof flashing is a thin metal material installed to direct water away from areas where your shingles butt up against something (walls, chimneys, valleys, etc.). To prevent leaks, flashing is installed around the chimney where it's connected on the roof.
This ensures the space where the chimney comes through the roof is sealed and watertight when water flows down. However, the type of roof flashing installed around a chimney depends on the material.
Step flashing
Step flashing is primarily used around chimneys made of siding or paneling. It works by placing individual L-shaped metal flashing pieces under every shingle that’s installed right up against the chimney and putting the other end under the siding.
It's installed step-by-step where the individual pieces create a metal channel between the shingles and chimney. Because the flashing is installed under the siding and shingles, it won't be visible once everything is finished.
Counter flashing
Counter flashing is used on chimneys like step flashing, but on brick or stone chimneys. This kind of flashing is sawed into the existing mortar with the metal over the brick and the other end under the shingles.
There's usually a sealant around the edges of flashing that's sawed into the brick as well. Counter flashing has the step-by-step look like step flashing, but it's actually visible instead of being under of everything.
Apron flashing
Apron flashing is used at the base of a chimney facing the eaves if the chimney doesn't end at the gutter line. It’s a long L-shaped piece of metal that goes the full length of the chimney's base.
If it's a brick chimney, the metal will be sawed into the mortar. However, apron flashing goes over the shingles instead of under them like step and counter flashing.
Roof cricket
A roof cricket is a double triangle structure built behind a chimney to divert water around it properly. So, it goes hand-in-hand with flashing to prevent chimney leaks.
A cricket ensures water splits down each side instead of pooling and backing up when it hits the flat wall of the 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.
According to code R903.2.2: A cricket or saddle must be installed on the ridge side of any chimney or roof penetration more than 30 inches wide as measured perpendicular to the slope. The cricket or saddle coverings also shall be sheet metal or of the same roofing material as the roofing covering.
Simply put, a cricket ensures water can continue flowing down your roof properly once it hits the back of your chimney.
What actually causes a chimney leak?
After learning about what prevents chimney leaks, you need to understand why it's happening. This is especially true because many chimney leaks aren't always a roofing problem.
Let's look at the following reasons why a chimney leaks:
- Flashing problems
- Lack of roof cricket
- Brick saturation
- Water through a damaged top or cap
Flashing problems
Flashing problems are the main cause of chimney leaks from a roofing perspective. 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.
Lack of roof cricket
As you know water can pool and back up behind the flat side of a chimney without something there to divert the water around. So, if you have large chimney over 30 inches, it may be leaking because it doesn't have a cricket.
Unfortunately, it's still possible for a leak without a cricket on a smaller chimney that doesn't require one per code. If you've had chimney leaks in the past, a roofer may recommend a cricket to try to stop the problem.
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. To fix this, you'll need to seal the bricks with a masonry water repellent that prevents water from saturating the bricks and mortar.
Water through a damaged top or cap
A chase top stops water from coming straight down into the chimney when it rains. If the chase is lower in the middle than the rest of the steel panel, it’s going to hold water, rust, and drip into into your home.
A leak can cause also happen if caulk fails around the hole that the chimney pipe comes through or if the cap gets damaged.
What other materials does a roof need to prevent leaks?
After reading this article, you now know what goes around your chimney to prevent leaks. Both roof flashing and crickets are crucial when it comes to chimneys and other large penetrations.
Without one or the other, you're looking at big leaks. However, they're just part of the roofing puzzle that prevents water from getting into your home.
Every components and material plays a role when they come together to make a watertight seal on your home. And missing just one leads to costly problems.
That's why I wrote another article breaking down all the crucial roofing materials that a roof needs to prevent leaks.
Check out 9 Materials Included With Your Roof Replacement to learn all the parts of your roof system, why they're important, and how they work.
