Chimney cricket: why some chimneys need one and most leak without it
A cricket is the one chimney detail most homeowners have never heard of. Until debris starts piling up behind their chimney every single autumn.
A chimney cricket (sometimes called a saddle) is a small, ridged structure built into the roof directly behind a chimney, on its uphill side. Its only job is to split the water and debris coming down the slope. It sends both around the chimney instead of letting them pile up against the back of the masonry.
Most narrow chimneys near a ridge never need one. Wide chimneys sitting partway down a long slope almost always do. And a huge number of them were built without one.
Why a chimney needs a cricket at all
Picture everything landing on a roof above a chimney: rain, granules washed off the shingles, leaves, pine needles, and in winter, snow and ice. On a plain slope all of that keeps moving downhill. A chimney interrupts that flow. If the chimney is narrow, water simply parts around it the way it parts around a narrow rock in a stream.
If the chimney is wide, the water and debris arriving at its uphill face have nowhere to go: they pond, they pile up. And they sit directly against the masonry and the flashing for as long as it takes to dry out, which after repeated storms is never quite long enough.
Does your chimney need one?
Most adopted US residential building codes use a width threshold, measured across the up-slope face of the chimney, perpendicular to the roof. Above roughly 30 inches, a cricket (or an equivalent saddle) is required. Below that width, the flashing alone is usually considered adequate.
The exact figure and the way it's measured can vary by the edition of the code your local jurisdiction has adopted. So treat 30 inches as the number to be suspicious around, not a guarantee either way. A permitted roofer or your local building department can confirm what applies to your chimney.
What a missing or failing cricket looks like from the ground
You do not need to get on the roof to get a good read on this. Stand back in the yard, ideally with binoculars, and look at the uphill side of the chimney: the side the water and debris are coming from.
- A dark, damp patch that never quite dries, even days after the rest of the roof has dried out.
- Visible debris built up in a wedge shape against the back of the chimney: leaves, needles, moss, or granules that should have washed past.
- A line of moss or algae tracing exactly where standing water has been sitting longest.
- Snow that lingers behind the chimney well after the rest of the slope has cleared, in a cold-climate winter.
Inside the house, the tell is a stain on the ceiling on the uphill side of the chimney, not beside or downhill of it. That is the opposite of most step-flashing leaks, which tend to show up level with or just below the chimney.
Two ways a cricket gets built
A cricket is either built up, framed in wood on site to the right pitch and covered in the same material as the rest of the roof. Or it is a prefabricated metal saddle set in place and flashed like any other roof-to-wall junction. Both are legitimate. What matters is that the cricket's own flashing ties properly into the chimney's counter-flashing, the same detail that has to be right on a plain chimney with no cricket at all.
Why a cricket that exists can still fail
Having a cricket is not the end of the story. Three things make an existing cricket leak anyway: it was built with too shallow a pitch to actually clear water and debris.
So it pools instead of shedding. Or its flashing was never properly integrated with the chimney's counter-flashing, leaving a seam exactly where the water concentrates. Or, on an older built-up cricket, years of trapped moisture have rotted the wood framing underneath sound-looking shingles. None of these are visible from inside the house until the leak is already well established.
Who to call
A cricket is a roofing detail, not a masonry one: it's built and flashed as part of the roof covering. That puts it squarely in a roofer's scope, distinct from the crown, cap, and mortar joints of the chimney itself, which are chimney and masonry work.
Suppose you have already ruled out those other three sources (see the general chimney guide linked below). A wide chimney with no visible cricket and a persistent damp patch on its uphill side is then a strong lead. Mention it by name when you call someone out.
And as with every page on this site: none of this requires climbing up. A pair of binoculars from the yard, a look at the ceiling from the inside. And a walk around the attic with a flashlight tell you almost everything you need before anyone sets foot on a ladder.
Frequently asked questions
What is a chimney cricket?
A small ridged structure built into the roof on the uphill side of a chimney. It splits the water and debris coming down the slope and routes it around both sides of the chimney instead of letting it pile up against the back of the masonry.
Do all chimneys need a cricket?
No. Narrow chimneys, especially near the ridge, generally don't need one because water parts around them on its own. Most US codes use a width threshold around 30 inches, measured across the up-slope face: wider than that and a cricket is typically required. Confirm the exact figure with a local roofer or your building department.
How can I tell if my chimney is missing one?
Look at the uphill side from the yard, ideally with binoculars: a damp patch that never fully dries, a wedge of built-up debris, or a line of moss tracing where water has been sitting are all signs. Inside, a ceiling stain that appears on the uphill side of the chimney, rather than beside or below it, points the same way.
Can a chimney leak even with a cricket in place?
Yes. A cricket built with too shallow a pitch won't shed water and debris properly, and if its flashing was never tied correctly into the chimney's counter-flashing, that seam becomes the leak point. On older built-up crickets, the wood framing underneath can rot for years before shingles above show any sign of it.
Is a cricket a roofing job or a chimney job?
Roofing. A cricket is built and flashed as part of the roof covering, which puts it in a roofer's scope. Unlike the crown, cap, or mortar joints of the chimney itself, which are masonry and chimney work.
Sources
What this page explains is based on these official sources. If you check one and it does not match what you read here, send it to us and the article gets corrected.
- NRCA. National Roofing Contractors Association
- US OSHA. 1926.501 — Duty to have fall protection (OSHA)