What's In This Article
What a Chimney Cricket Is
A chimney cricket — also called a saddle or a diverter — is a small peaked roof structure built behind the chimney, on the uphill side of a sloped roof.
Its shape is a simple ridge running back from the chimney into the slope, forming two small planes that shed water left and right.
Its job is one sentence: send water and debris around the chimney instead of into it.
What Happens Without One
Picture a wide chimney sitting in the middle of a sloped roof, with no cricket. Everything coming down that slope — rain, snowmelt, leaves, pine needles, grit — hits the back wall of the chimney and stops.
What accumulates there:
- Leaves and debris pile up in the corner and hold moisture against the masonry permanently. Not "when it rains" — permanently.
- Water pools behind the chimney instead of running past it.
- Snow and ice accumulate in exactly that spot, and stay there longest.
Now consider what's in that corner: the flashing. The strip of metal where the chimney meets the roof — the single most failure-prone detail on any roof — is being asked to sit permanently in a wet, debris-filled trough.
Debris collects behind chimney → moisture held against flashing and masonry year-round → flashing corrodes and seal fails → water enters roof deck and wall cavity → interior leaks appear years later, and by then the damage in the cavity is substantial. The homeowner sees a ceiling stain and assumes it just started. It didn't.
The Code Requirement
The International Residential Code requires a cricket or saddle on the upper side of any chimney that is more than 30 inches wide where it meets a sloped roof.
Thirty inches is not a large chimney. Plenty of ordinary masonry chimneys exceed it comfortably.
The catch: that requirement applies to new construction and permitted work. It is not retroactive. So a wide chimney on a house built decades ago may well have no cricket at all — entirely legally — and the homeowner has no idea anything is missing.
If your chimney is wider than about two and a half feet and there's nothing behind it, that's not a code violation. It's just a leak that hasn't happened yet.
South St. Louis: Building One From Scratch
The build is straightforward in principle and unforgiving in execution. The ridge has to run true, the two planes have to pitch enough to drain properly, and the whole thing has to tie into the existing roof deck as a continuous surface — not sit on top of it.
The flashing integration is the part that matters most and shows least. The cricket's shingles, the roof's shingles, and the chimney's counter-flashing all have to layer in the correct order so that water is always being handed outward and downward. Get that sequence wrong and you've built a very well-shaped funnel.
Adding a Cricket to an Existing Chimney
You do not need to be re-roofing to add a cricket, though that's the cheapest moment to do it — the shingles are off anyway and the flashing is being redone regardless.
On an existing roof, we open up the area behind the chimney, frame the cricket into the deck, and re-integrate the shingles and flashing around it. It's a contained job.
Who should seriously consider it:
- Any chimney wider than about 30 inches with nothing behind it
- Anyone who has had a persistent chimney leak that keeps coming back after flashing repairs — see why leaks recur
- Anyone with visible debris permanently packed behind the chimney
- Anyone re-roofing a house with a wide chimney — do it now, while the roof is open
Related Pricing — AIO Pro Chimney
A cricket costs a fraction of what water damage in a wall cavity costs, and it is the rare repair that stops a problem from ever starting rather than cleaning up after one.
Frequently Asked Questions
What is a chimney cricket?
A chimney cricket — also called a saddle or diverter — is a small peaked roof structure built behind the chimney on the uphill side of a sloped roof. It diverts rain, snowmelt and debris around the chimney instead of letting them collect against the back wall.
Is a chimney cricket required by code?
The International Residential Code requires a cricket or saddle on any chimney more than 30 inches wide where it meets a sloped roof. However, the requirement applies to new construction and permitted work and is not retroactive, so many older homes with wide chimneys have none.
What happens if my chimney doesn't have a cricket?
Water, leaves and snow collect in the corner behind the chimney and hold moisture permanently against the flashing and masonry. That accelerates flashing failure, and once the flashing goes, water enters the roof deck and wall cavity — often for years before an interior stain appears.
Can a cricket be added to an existing roof?
Yes. We open the roof behind the chimney, frame the cricket into the deck, and re-integrate shingles and flashing around it. It's most economical during a re-roof, since the shingles and flashing are being replaced anyway, but it can be done any time.
How much does a chimney cricket cost?
It depends on chimney width, roof pitch and access, so we quote it after inspecting. Written estimates are always free. For context, it is a small fraction of what hidden water damage in a wall cavity costs to repair.
Wide Chimney With Nothing Behind It?
We'll look at the back of your chimney and tell you honestly whether a cricket is worth building. Free inspection, free written estimate.
