Your roofing system and its surrounding parts may be prone to leaks. And a potential roof leak area is around your chimney. That’s why roofing contractors have certain materials and techniques to keep water out of your home. So, what is placed around a chimney to prevent leaks?

We will talk about it and general chimney maintenance in this article. 

What is placed around a chimney to prevent leaks?

The answer is flashing – the metal sheet installed where the chimney meets the roof. It ensures that the point of contact between your roof and the chimney is completely sealed and watertight so as to prevent roof leaks and water damage.

Also, roof flashing helps to direct water away from your roof, including the chimney. Just like a roof inspection, your chimney too needs regular inspections for leaks. 

Types of roof flashing for a chimney

roof flashing

There are different types of roof flashing or roofing materials placed around a chimney to prevent leaks and protect the chimney from water damage.

Step flashing

Roofing experts use step flashing against the sides of walls and chimneys. They place a piece of metal (flashing) under every roof shingle installed against the side of a wall. This successfully blocks the water from running down into it. 

That is to say, you install a shingle first, then a piece of flashing, then another roof shingle, and then a piece of flashing – until the wall is covered and is protected completely. 

Apron flashing 

This type of roof flashing is used at the base of a wall, penetration, or around dormers. The flashing is like the letter L. It can be up to 14 feet in length to fit the base of the penetration. It even prevents water from getting into your house windows.

Counter flashing 

Counter flashing is similar to step flashing. That is to say, it’s used on walls and chimneys. However, this piece of flashing is sawed into an existing mortar joint. The metal then comes over the top of the brick.

Roof crickets 

roof crickets

A roof cricket, a double triangle structure, too protects the roof by channelizing the water flow into a proper path so that it gets to your rain gutters, and doesn’t lead to a roof leak. In fact, in 2012, the IBC (International Building Code) made cricket installation a building code. All chimneys over 30 inches wide must have a roof cricket installed perpendicular to the roof’s slope.

So, how does it work? As the water comes down the roof, it hits the cricket behind the chimney and splits down each side instead of hitting the wall of your chimney. This prevents water from pooling behind the chimney.

Keep in mind that once your roof starts to leak, it can be quite costly to repair the damage. Therefore, it’s better to install a roof cricket and ensure that your roof is up to code. If you’re getting a roof replacement through homeowners insurance and have a code upgrade coverage policy, your insurance company may pay to install a roof cricket. 

What are the causes of a chimney leak?

There are primarily two reasons your chimney may be leaking. 

The first one is that the roof flashing may have been improperly installed. The second reason is that the flashing around your chimney has reached the end of its lifespan or is damaged. Apart from these, there could be other reasons too – all of which we will explore below.

Chimneys can leak for various reasons. Learning about these causes and their solutions will help you take action in the early stages of a roof leak or water damage in all areas of your roof.

Damaged flashing 

One of the most common causes of a leaking chimney is a cracked caulk that otherwise seals the flashing. If the flashing is damaged, it will not seal the point of contact between the chimney and the roof properly. As a result, the wear and tear will allow water to seep in. Thankfully, newer chimney flashings are made from aluminum or copper which can last a long time – unlike steel flashing in older homes which could rust more easily. 

Solution: Hire a professional to check your flashing during a roof inspection. If the caulk or flashing is damaged, replace the flashing with fresh caulking. 

Missing chimney cap 

A chimney cap helps block water, wildlife, or debris from entering the opening at the top of your chimney. 

Solution: Repair or replace a damaged or missing chimney cap to protect your chimney and your home from further water damage. It will also prevent debris build-up.

Damaged chimney crown

chimney crown protecting against snow

If the chimney crown, a slab that covers a big part of the top of the chimney, is cracked, it could cause a leak. It has a downward slope to guide water away from the top of the chimney and helps prevent brick-and-mortar erosion. 

Solution: A professional inspection would help identify chimney crown damage. The professional will then rebuild the eroded parts of the chimney.

Damaged bricks or mortar

Cracked or damaged bricks and mortar can let water enter the chimney, causing a leak. The problem worsens in colder weather when the water expands and causes the cracks to widen. 

Solution: If you see any damage where the bricks and mortar meet, the particular bricks will need repair or replacement. 

Last thoughts

Now you know roof flashing is placed around a chimney to prevent roof leaks and other types of water damage. This flashing helps to keep water away from pooling on your roof or around the chimney by ensuring that the chimney exit is sealed and watertight. On your part, you need to make sure that the roof flashing is installed properly and is not damaged in any way.

Know what is placed around a chimney to prevent leaks was last modified: December 13th, 2022 by Ramona Sinha
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