Chimney Cricket Installation — When Your Roof Needs One

What a Chimney Cricket Is and What It Does

A chimney cricket is a peaked structure — essentially a small ridged roof — built on the uphill side of a chimney where it intersects the main roof slope. The ridge of the cricket runs from the center of the chimney back face outward to each corner, forming two sloped planes that shed water to the left and right of the chimney rather than into the pocket behind it.

Without a cricket, the geometry of a chimney penetration creates a problem. The back face of the chimney — the side facing up the slope — forms a right-angle pocket with the roof surface. That pocket collects everything: rainwater, blown leaves, pine needles, ice, and snow. On a steep pitch it drains slowly. On a low-slope section or a wide chimney, it can hold standing water for hours after a rain event. Water sitting in that pocket works against every joint in the flashing assembly, looking for a path through. Given enough time and enough freeze-thaw cycles, it finds one.

The cricket eliminates the pocket entirely. Water hits the cricket's two sloped faces and runs off to either side, where it integrates with the step flashing and flows into the gutter system. The chimney back face never sees standing water. The flashing joints never bear the load they would bear without the cricket. The result is a fundamentally more watertight assembly at one of the most leak-prone locations on any residential roof.

How the Cricket Integrates with Flashing

A chimney cricket does not work in isolation. It is part of a four-component flashing assembly: step flashing on the sides of the chimney, base flashing at the front (low side), counter flashing embedded in the chimney mortar joints on all four sides, and saddle flashing that seals the junction between the cricket and the chimney back face. The cricket provides the structural substrate; the saddle flashing makes the cricket-to-chimney joint watertight.

The saddle flashing wraps the peak of the cricket and laps up behind the counter flashing on the back face of the chimney. On a sheet metal cricket, the saddle is typically soldered directly to the cricket body. On a built-up wood cricket, the saddle is a separate piece of sheet metal — usually 26-gauge galvanized steel, lead-coated copper, or copper — that is nailed and sealed at the cricket peak and integrated into the shingle courses on the cricket faces.

For detailed flashing requirements that apply across the entire chimney perimeter, see our chimney flashing installation guide and our flashing technical standards page.

When Building Code Requires a Chimney Cricket

The trigger for a required cricket is the chimney width as measured perpendicular to the roof slope. Both the International Residential Code (IRC Section R903.2.2) and the International Building Code (IBC Section 1503.5) state the same rule: any chimney wider than 30 inches on its uphill face requires a cricket or saddle. Georgia has adopted the IRC statewide. Gwinnett, Fulton, Cobb, and Cherokee counties — the core of the Atlanta metro area — all enforce it.

The 30-inch threshold is not arbitrary. Chimneys narrower than 30 inches present a small enough back-face exposure that properly installed step and counter flashing, combined with adequate slope, can manage the water load without a cricket. Once the chimney width exceeds 30 inches, the area of the water-collecting pocket grows faster than the drainage capacity of the flashing joints. The code requirement is a recognition of that geometry.

Measuring Correctly

The 30-inch measurement is taken across the chimney face that faces uphill — the back of the chimney as viewed from the ridge. Many chimneys that look narrow from the front or sides are actually wider than 30 inches at the back. This matters on a re-roof: if the existing chimney never had a cricket because it was built before the IRC was adopted locally, the new roof installation requires one if the chimney meets the 30-inch threshold.

Contractors who skip this measurement and install a re-roof without a required cricket are creating a code violation and, more practically, leaving the homeowner with a flashing assembly that is undersized for the load it will carry. On a premium Atlanta home where the chimney is built from full-depth masonry — common on high-end construction in Buckhead, Sandy Springs, and Johns Creek — the back face is often 36 to 48 inches wide. A cricket is not optional on those chimneys.

Re-Roofing vs. Repair

A full roof replacement is a permit-pulling event in most Georgia jurisdictions, and an inspector will check for the presence of a cricket on any chimney that exceeds 30 inches. A repair that addresses only damaged shingles in a limited area does not trigger the same code review. That distinction matters from a project-scoping standpoint, but it does not change the physics: a wide chimney without a cricket is leaking or will leak, regardless of whether a permit inspection is involved.

How Missing Crickets Cause Water Damage and Ice Damming

The pocket behind a chimney without a cricket is a water trap. On a roof with a moderate slope, rainwater drains through it reasonably well during a normal rain event — but normal is not the design condition that matters. What matters is an extended rain, a clogged gutter, or two inches of wet leaves that slow drainage to a standstill. Under those conditions, the pocket holds water against the base of the chimney for hours. The flashing at the base of that back face is the only thing standing between that water and the interior of the home.

Chimney flashing — even good chimney flashing — is not designed to hold standing water. It is designed for a dynamic condition where water sheds. The sealants and lap joints in a flashing assembly are waterproof under moving water; they are not a dam. When water sits against a lap joint long enough, it wicks through. The first sign of this is often a water stain on the ceiling near the fireplace, which homeowners frequently attribute to the chimney cap or crown — not recognizing that the actual entry point is the base flashing assembly in the back pocket.

Ice Damming Behind the Chimney

Atlanta homeowners do not think much about ice damming because hard freezes are infrequent. But they happen — 2022 and early 2024 both produced extended sub-freezing periods across the metro area — and when they do, the chimney back pocket is one of the highest-risk ice dam locations on a residential roof.

The chimney mass stores and radiates heat differently than the surrounding roof deck. On a cold night following a day of snowmelt, the edges of the snowpack near the chimney can refreeze before the center melts. The result is a localized ice dam precisely at the chimney back face — exactly where standing water was already a concern. Ice that forms in the chimney pocket expands into the flashing joints as it grows. This is a different failure mode than the flashing simply corroding or the sealant aging out: it is a mechanical forcing of the joint that can displace step flashing, crack counter flashing, and introduce gaps that never existed before the freeze event.

A cricket solves this too. When there is no flat back pocket to collect snow and ice, the freeze-thaw cycle has no geometry to exploit. Snow sheds to the sides. Water moves. There is no place for ice to accumulate and build pressure.

Debris Accumulation

On wooded lots — the norm in Buckhead, Roswell, and Johns Creek — the chimney back pocket collects leaves, pine needles, and twigs continuously. This organic material holds moisture against the flashing, accelerates sealant degradation, and can physically block drainage entirely after a single season. A chimney that might manage adequately in an open suburban setting can produce active leaks after two years on a wooded lot, purely because of debris loading. The cricket eliminates the collection surface entirely.

Cricket Material Options: Metal vs. Built-Up Construction

A chimney cricket can be built two ways: as a framed wood structure sheathed and covered with shingles or metal flashing, or as a fully fabricated sheet metal assembly. The right choice depends on chimney size, roof pitch, budget, and how long the homeowner wants to go between maintenance cycles.

Built-Up (Framed) Cricket

A built-up cricket uses dimensional lumber — typically 2x4 or 2x6 material depending on the cricket height required — to frame the peaked structure. The frame is sheathed with OSB or plywood, covered with synthetic underlayment, and then finished with either matching shingles or a sheet metal saddle cap.

When finished with shingles, the cricket blends into the surrounding roof and is practically invisible from ground level. The shingles on the cricket faces require the same maintenance schedule as the rest of the roof — they age, they can sustain hail damage, and they need to be replaced with the roof. The advantage is cost: a built-up cricket is generally less expensive to construct than a fabricated metal cricket, especially on larger chimneys where a metal cricket would require significant sheet metal work.

The limitation of a built-up cricket is the number of joints in the assembly. Every joint between the shingles, the saddle flashing, the step flashing, and the counter flashing is a potential water entry point. Each of those joints requires sealant that has a finite service life. A built-up cricket done correctly will perform well for 15 to 20 years; one done with marginal workmanship will show problems within five.

Sheet Metal Cricket

A sheet metal cricket is fabricated from a single material — copper, lead-coated copper, stainless steel, or 26-gauge galvanized steel — cut and formed to fit the specific chimney geometry. The seams are soldered rather than sealed, eliminating the sealant aging problem entirely. A properly soldered copper cricket has an effective service life that matches or exceeds the masonry chimney itself.

Copper is the premium choice and the right specification for high-end Atlanta homes. It requires zero maintenance, develops a protective patina that actually improves its corrosion resistance over time, and is visually distinctive in a way that signals quality craftsmanship to the next buyer. Lead-coated copper provides similar performance at lower cost and is the specification most often used by commercial roofing contractors on institutional buildings.

Galvanized steel sheet metal crickets are a workable option at lower price points. The limitation is longevity: galvanized coatings degrade in humid climates, and a galvanized steel cricket on an Atlanta home should be expected to last 20 to 25 years before it needs replacement — less than half the service life of a copper assembly. For a home where the chimney and roof are both being redone as a long-term investment, the cost difference between galvanized steel and copper is almost always worth paying.

Sizing the Cricket

The height of a chimney cricket is determined by the chimney width and the roof pitch. On a standard 6/12 pitch, a 36-inch-wide chimney requires a cricket that is 9 inches tall at the peak — enough rise to shed water at an angle steeper than the main roof slope. Under-height crickets are a common installation deficiency: a cricket that is too shallow does not generate sufficient slope to drain effectively and fails to solve the problem it was built to address.

GAF Requirements for Chimney Cricket Installation with Timberline Shingles

GAF publishes technical installation details for every significant roof assembly condition. For chimney cricket installation with Timberline Series shingles, the governing document is Detail SSTS08. This detail defines the specific flashing configuration, material specifications, and integration sequence required for a GAF-warranted chimney installation on a roof wider than 30 inches at the chimney back face.

Key Requirements from SSTS08

The SSTS08 detail specifies that the cricket structure itself must be properly sloped to drain — GAF does not define a minimum slope for the cricket faces explicitly, but the installer warranty requirements imply a workmanlike standard consistent with shedding water effectively. The following elements are required under the detail:

• Step flashing at each side of the chimney, minimum 4 inches on the roof surface and 4 inches up the chimney face, with each piece overlapping the one below by at least 2 inches
• Base flashing at the downhill (front) face of the chimney, lapped over the last course of step flashing on each side
• Saddle flashing at the cricket peak and back face of the chimney, integrated with the counter flashing above and the step flashing on each side
• Counter flashing embedded a minimum of 1 inch into a raked mortar joint, then sealed — not merely surface-applied with sealant alone
• All metal flashing to be corrosion-resistant: aluminum, galvanized steel, copper, or lead-coated copper
• Cricket shingle courses — if shingles are applied to the cricket faces — to be installed with full nail penetration into solid sheathing, not into the framing members alone

GAF's Silver Pledge warranty, which 1 Source Roofing carries as a certified contractor, covers both materials and workmanship. A cricket that fails to meet the SSTS08 requirements is a workmanship deficiency that the contractor — not GAF — bears responsibility for correcting. This is why specification compliance matters: a homeowner with a Silver Pledge warranty is protected only if the installation was done correctly in the first place. Shortcuts on the cricket assembly are not covered by manufacturer warranty.

For the broader context of flashing standards that apply across all roof penetrations and terminations, see our flashing technical standards page.

What Goes Wrong When a Cricket Is Missing or Poorly Built

The failure modes at a chimney without a proper cricket follow a consistent pattern. Understanding them is useful not only for contractors but for homeowners trying to evaluate an existing roof or a re-roofing proposal.

Counter Flashing Pushed Out of the Mortar Joint

Counter flashing that is embedded in the chimney mortar relies on the mortar to hold it in compression. Standing water in the back pocket saturates the mortar joint over time, softening it and reducing its grip on the counter flashing. Freeze-thaw cycles then pry the counter flashing outward. Once the counter flashing lifts even a fraction of an inch, the seal behind the step flashing is broken. Water enters not at the visible front face but at the back corner junctions, which are the most difficult joints to inspect without getting on the roof.

Step Flashing Corrosion at the Pocket Base

The bottom course of step flashing at the chimney back corners sits at the lowest point of the water-collecting pocket. On a chimney without a cricket, this is also the highest-moisture location on the roof. Galvanized step flashing in this position can corrode through in as few as 10 years on a wooded lot in Atlanta's humid climate. Aluminum step flashing resists corrosion better but is susceptible to galvanic corrosion if it contacts the copper counter flashing that some masons install. Either way, the step flashing at the base of the back pocket is the first piece to fail and the last piece a homeowner would think to inspect.

Sheathing and Rafter Rot

A slow leak at the chimney back flashing assembly typically does not produce a visible drip through the ceiling. It drips onto the attic side of the roof sheathing, where it is absorbed and held by the wood fiber. The sheathing around the chimney stack gradually softens. The moisture wicks along the sheathing grain to the nearest rafter. The rafter begins to lose section. By the time a homeowner notices a ceiling stain or a soft spot in the roof when walked, the structural repair cost has grown well beyond what the initial cricket installation would have cost.

On a home with plywood sheathing, the delamination is relatively rapid and obvious when the roof is stripped during replacement — you can see the layers separating near the chimney. On older homes with board sheathing, rot can be localized enough that the damage is easy to miss until a foot goes through during re-roofing. Either way, discovering it at re-roofing time means additional cost and delay that a cricket would have prevented entirely.

Under-Height or Flat Crickets

A built-up cricket that was framed with insufficient height is nearly as bad as no cricket. A flat or nearly flat cricket does not drain — it just creates a larger, flatter water-collecting surface instead of the original narrow pocket. The water load on the flashing assembly increases rather than decreases. These installations are common on older re-roofing jobs where a cricket was technically present but was built by a crew that did not understand the geometry requirements. From the ground, the cricket looks correct. From the roof, the slope of the cricket faces is clearly inadequate.

How 1 Source Roofing Installs Chimney Crickets on Atlanta Homes

Our chimney cricket work follows a defined sequence on every job. The sequence is not improvised on the roof based on what materials are on hand — it is the same process every time, matched to the specific chimney dimensions and the GAF SSTS08 requirements for Timberline shingle installations.

Site Assessment and Cricket Specification

Before the roof tear-off begins, the crew lead takes two measurements at the chimney: the back-face width perpendicular to the roof slope, and the roof pitch in that area. Those two numbers determine the required cricket height and the cricket geometry. On a 6/12 pitch roof with a 42-inch-wide chimney, the cricket peak needs to be at least 10.5 inches above the roof surface at the chimney back face. We calculate this before the first shingle is removed so materials are staged correctly.

We also inspect the existing chimney crown and cap at this stage. A cricket solves the water management problem at the roof surface, but a deteriorated chimney crown or a missing cap lets water in from the top. Both issues need to be addressed. We document the crown and cap condition in the project photos regardless of whether we are engaged to address them — the homeowner should know the full picture.

Tear-Off and Inspection

When the existing shingles and underlayment are removed from the chimney area, we expose the existing flashing assembly and the roof sheathing beneath it. We check every piece of step flashing for corrosion and document its condition. We check the sheathing around the chimney stack for soft spots, delamination, and rot. Any sheathing that is compromised gets replaced before the new assembly goes down — we do not shingle over rot.

We also check the condition of the counter flashing embedded in the mortar joints. If it is loose, we re-set it with new mortar and allow adequate cure time before the new step flashing is integrated. If the masonry itself is deteriorated, we note that in the project documentation and discuss repair options with the homeowner before proceeding.

Cricket Framing and Sheathing

For chimneys up to approximately 48 inches wide, we typically frame the cricket on-site using kiln-dried dimensional lumber. The two ridge members run from the peak of the cricket to each corner of the chimney back face at the correct slope. We sheath the cricket faces with 7/16-inch OSB and cover the entire assembly with GAF WeatherWatch ice-and-water shield before any metal flashing or shingles are applied. On a chimney in a location that is prone to ice accumulation, we extend the WeatherWatch down the adjacent roof areas to provide a secondary waterproof membrane behind the flashing assembly.

For larger chimneys or premium applications, we specify a fabricated metal cricket. Our sheet metal work uses 24-gauge copper or 26-gauge galvanized steel depending on the budget. The cricket is measured, cut, and formed off the roof and lifted into position as a single unit. The seams are soldered on-site after installation.

Flashing Integration

Step flashing is installed first, working from the bottom up on each side of the chimney. Each piece of step flashing is nailed to the roof deck — not to the chimney — and embedded under the adjacent shingle course. The saddle flashing at the cricket peak is installed next, lapping over the top of the step flashing on each side and extending up behind the counter flashing on the chimney back face. Counter flashing is then set in freshly raked mortar joints and bent down over the saddle and step flashing with a 2-inch minimum overlap.

All exposed lap joints receive a bead of roofing sealant compatible with the flashing material. We do not substitute sealant for proper lap geometry — the sealant is the secondary seal on a correctly lapped joint, not the primary waterproof barrier.

For complete documentation on our flashing installation approach across all chimney and penetration types, see our chimney flashing installation guide. For homeowners beginning a full roof replacement project, our roof replacement service page explains how we scope and price full re-roofing work in Atlanta.

Chimney Crickets and Insurance Claims in Georgia

Water damage at the chimney back flashing is one of the more common interior water damage claims on high-end Atlanta homes. Whether that damage is covered depends on two questions: what caused the water entry, and when did it start?

Georgia homeowner policies generally cover sudden and accidental water intrusion — water that enters due to a discrete storm event rather than a gradual condition that developed over time. A hail storm that damages the counter flashing at the chimney, a wind event that lifts the saddle flashing, or a freeze event that forces ice into the flashing joints are all potentially covered events. In those scenarios, the claim documentation needs to establish that the water entry resulted from the storm event rather than a pre-existing condition that the storm merely made visible.

When a Missing Cricket Complicates a Claim

A missing cricket on a chimney wider than 30 inches is a building code deficiency. Adjusters who inspect chimney water damage often note the absence of a required cricket in their reports. The question is whether the insurer treats that absence as a maintenance deficiency — which would exclude the claim — or as a contributing factor in an otherwise covered storm loss.

In our experience working with adjusters across the Atlanta metro area, the outcome depends heavily on how the claim is documented. If the visible damage at the chimney can be tied to the storm event — displaced flashing, cracked masonry, ice-pushed joints — and the claim is documented with photographs and weather data, the storm damage is frequently covered even when the cricket was absent. What is not covered is the gradual deterioration that accumulated in the years before the storm.

The practical implication: if your home has a wide chimney, no cricket, and you are filing a storm damage claim that includes chimney-area damage, having a GAF-certified contractor document the flashing assembly conditions before and after the storm is worth doing. We provide that documentation as part of our flashing inspection and installation service and our storm damage claims assistance work.

Post-Claim Cricket Installation

When a chimney flashing claim is approved and we are engaged to do the repair work, we treat the project as an opportunity to bring the entire chimney assembly up to current code and GAF specification — not just to replace the damaged components. That means installing a properly sized cricket if one was absent, re-setting loose counter flashing, and replacing any corroded step flashing. Repairing the immediate damage without addressing the underlying geometry is a short-term fix; addressing both produces a result that will perform for the life of the shingle system.

Technical Bulletins from GAF and CertainTeed

The information on this page is backed by official manufacturer technical bulletins. These documents provide the installation specifications, warranty requirements, and best practices that certified contractors like 1 Source Roofing follow on every project.

• GAF Timberline Series — Chimney Cricket Installation Detail (PDF)
• GAF Timberline Series — Chimney Flashing Detail (PDF)
• GAF Sovereign Series — Chimney Flashing Detail (PDF)