By Johnathan Mason, Ace Chimney Service.
If your chimney comes through the middle or the upslope side of the roof and it is wide, there should be a small peaked structure built behind it. It is called a cricket, or a saddle, and its absence is one of the more common causes of persistent leaks that no amount of resealing ever fixes. Worth knowing about in Island Lake, where wind-driven rain finds every weakness.
The problem it solves
A chimney passing through a sloped roof creates a dam. Everything running down the roof above it — rain, melting snow, ice, leaves, pine needles — hits the back wall of the chimney and stops there. Water pools against the masonry and the flashing. Debris collects and holds moisture in place. In winter, snow packs into that pocket and stays long after the rest of the roof has cleared, then melts and refreezes at the joint.
What a cricket does
A cricket is a small ridged structure framed behind the chimney, essentially a miniature roof shaped like a wedge, that splits water and sends it around both sides rather than into the joint. It also gives snow and debris nowhere to sit. It is flashed into the roof and into the chimney, and when built correctly you stop thinking about that side of the chimney entirely.
When one is required
The general threshold is chimney width measured across the slope: wide chimneys on sloped roofs need one, narrow ones generally do not. Building code language varies, so the practical version is this — if your chimney is more than about thirty inches wide where it meets a sloped roof, and there is no cricket behind it, that is worth investigating. Many houses were simply built without one.
How the leak shows up inside
Staining on the ceiling near the chimney chase, damp in the attic on the upslope side, a musty smell in that corner, rot in the roof sheathing or framing behind the chimney, and rusted flashing. Often the water shows up several feet away from where it enters, which is why these leaks get misdiagnosed as roof problems and chased for years.
How this connects to the rest of the chimney
The cricket, the flashing, the crown, and the cap are one water-management system, and a leak nearly always involves more than one of them. That is why our chimney repair work starts with finding the actual entry point rather than sealing the most obvious-looking gap. A proper chimney inspection includes the roof interface.
Cricket construction is roofing work coordinated with masonry, and it is autumn work — ahead of the freeze-thaw season, not during it. Ace Chimney Service has 29 years in the trade, is insured and bonded, and gives the price up front. Seven days a week, 7 AM to 7 PM, Crystal Lake and McHenry County. Call (815) 320-0883.
Frequently asked questions
What is a chimney cricket?
A small peaked structure built on the upslope side of a chimney that diverts water and debris around it instead of letting them pool against the masonry.
Does every chimney need one?
No. It matters for wider chimneys on sloped roofs. Narrow chimneys and those at the ridge generally do not require one.
How wide is wide enough to need a cricket?
The common threshold is around thirty inches measured across the slope, though local code and roof pitch affect it.
Can a cricket be added to an existing roof?
Yes. It is framed and flashed in as a retrofit, usually alongside replacing the surrounding flashing.
Is caulking behind the chimney a fix?
Only as a very short-term measure. Sealant fails, and it does nothing about snow and debris collecting there.
How do I tell if mine has one?
From the ground with binoculars you can often see the small peak behind the chimney. If the roof runs flat into the back of it, there is none.
Could my chimney leak have another cause?
Frequently. Crown cracks, a missing cap, failed flashing, and open mortar joints all cause leaks and are checked together.
Is this a roofer’s job or a chimney company’s?
It sits on the boundary, which is why the flashing and masonry side needs to be coordinated rather than done in isolation.
Published September 15, 2026