A chimney cricket is a small, peaked roof structure installed behind your chimney that splits water and snow to both sides so nothing pools at the base. In Lexington’s wet, snowy climate, a chimney cricket prevents leaks, rot, and cracked masonry. Building code generally requires one for chimneys wider than 30 inches, and it’s a professional job that ties into your chimney flashing. If you have recurring leaks behind the chimney, a cricket is often the real fix. If your chimney keeps leaking no matter how many times someone re-caulks it, the problem may not be the flashing at all.
It’s a small, peaked structure, sometimes called a saddle or diverter, that sits on the upslope side of your chimney. Its job is to split rainwater and melting snow and guide it around both sides of the chimney, so water never gets a chance to pool behind it. Without a cricket, water hits the back wall of the chimney, sits there, and eventually seeps into the roof, causing leaks, wood rot, and cracked masonry over time.
A chimney cricket is a small, ridged roof installed in Lexington, MA on the upslope side of a chimney to divert water and snow around it instead of letting them pool behind it. Also known as a chimney saddle or diverter, it creates two small slopes that send water down either side of the chimney and toward your gutters. It works together with your chimney flashing as a powerful second line of defense against leaks.
A roofer builds a cricket out of wood framing, covers it with ice-and-water shield, then finishes it with metal flashing or asphalt shingles that match your roof. The cricket ties directly into the chimney flashing system. While standard step and counter flashing seal the gap between the chimney and roof, they often can’t handle the heavy water and ice loads that build up behind a chimney. That’s where the cricket comes in.
Your roof needs a chimney cricket when the chimney is wide, sits on a steep or low-slope roof, or is located where water naturally collects behind it. Building code generally requires a cricket for any chimney wider than 30 inches. Homes in wet or snowy climates like Lexington also benefit from a cricket even when it isn’t strictly required.
One exception: if your chimney sits right at the roof’s ridge, you usually don’t need a cricket, because there’s no upslope area for water to pool. A professional roof inspection is the best way to know for sure.
The 30-inch rule states that building code requires a cricket or saddle on any chimney wider than 30 inches, measured on the side that runs parallel to the roof’s ridge. This has been part of the International Building Code since 2012, so chimneys this wide must have a cricket installed. The wide, ridge-facing side of the chimney is the most vulnerable to pooling water, which is why it’s measured that way.
If your Lexington roof was last replaced before 2012 and you have a chimney wider than 30 inches, you may not have a cricket at all. In that case, one should be built during your next roof replacement in Lexington, MA. If you’re dealing with ongoing leaks now, a roofer can also retrofit a cricket onto your existing roof. The code also ties the cricket’s height to your roof pitch: the steeper the roof, the steeper and taller the cricket.
Without a chimney cricket, water and snow pool behind the chimney and slowly work their way into your roof and home. Over time, this leads to roof leaks, wood rot, attic moisture, mold growth, and cracked chimney masonry. What starts as a small drainage problem can turn into major structural damage and costly repairs.
A chimney cricket is installed by framing a small peaked structure behind the chimney, covering it with waterproof underlayment, and finishing it with flashing and roofing material that ties into the rest of the roof. It’s a precise job that combines framing and roofing skill, which is why it should always be left to a professional. A poorly built cricket can cause more harm than having none at all.
A key detail: the cricket is never nailed to the chimney itself. Fastening only to the roof deck lets the two move independently as temperatures change, which prevents warping and future leaks. This is exactly the kind of detail an experienced roofing company in Lexington, MA gets right.
Lexington’s climate makes chimney crickets especially valuable. The local weather puts constant stress on the area behind your chimney.
Heavy snow and ice dams: Lexington winters pile snow against chimneys, and with around 100 freeze-thaw cycles a year, that snow refreezes into ice dams. A cricket keeps snow from collecting behind the chimney in the first place.
Freeze-thaw masonry damage: Water that pools behind a chimney soaks into the brick, then freezes and cracks the masonry. On historic Lexington homes, this kind of damage is expensive and hard to repair.
Older homes and roof maintenance: Many Lexington homes are older, and some pre-2012 roofs lack a proper cricket. Regular roof attic maintenance and inspection catch this before it causes a hidden leak or attic moisture problem.
At OneGuard Roofing, we build and install chimney crickets that protect Lexington homes from leaks for good. We handle the framing, flashing, and waterproofing correctly, so water always flows where it should. Honest work, done right.
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A chimney cricket is a small feature that makes a big difference. By splitting water and snow around your chimney, it prevents the leaks, rot, and masonry damage that plague chimneys without one. If your chimney is wide, sits on a steep or low slope, or leaks again and again, a cricket is often the lasting solution you’ve been missing.
In Lexington’s snowy, freeze-thaw climate, a properly built chimney cricket is one of the smartest upgrades you can make. If you’re planning a roof project or fighting a stubborn chimney leak, have a professional check whether your roof needs one.
