Chimney Crickets: Diverting Water and Snow Behind Chimneys

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The uphill side of a chimney is one of the hardest-working spots on any roof. Rain running down the slope, snow sliding off the ridge and meltwater from a sunny afternoon all collide with a wall of brick or siding and have nowhere to go. A chimney cricket, also called a saddle, is a small peaked framing structure built behind the chimney to split that flow and send it around both sides. When a cricket is missing, undersized or poorly flashed, the result is often a slow leak that shows up as a stained ceiling, damp framing in the attic or crumbling mortar. This guide explains what a chimney cricket is, when one is typically expected, why it matters so much on snowy Colorado roofs, how the flashing around it should work, what home inspectors look for and what repairs generally cost. Code requirements vary by jurisdiction, so local building officials have the final word on any specific house.

Part of our Structure & Exterior guide — start there for the full picture →

What a Chimney Cricket Is and What It Does

A chimney cricket is a small, ridge-shaped roof section that sits between the back (uphill) face of a chimney and the main roof slope. Seen from above, it looks like a tiny gable roof tucked against the chimney, with its peak pointing up the slope. Its job is simple: instead of letting water and snow pile up against a flat wall of masonry, the cricket deflects them sideways so they flow around the chimney and continue down the roof.

The American Society of Home Inspectors (ASHI) describes the cricket or saddle as a peak that deflects water and snow around the chimney, preventing it from accumulating against the top side of the chimney. ASHI also notes that the cricket is usually framed from the same material as the roof sheathing, which in modern construction means plywood or oriented strand board. It is then covered with underlayment and either the same roofing as the main roof or sheet metal, and tied to the chimney with flashing.

Without a cricket, the area behind a wide chimney behaves like a dam. Water slows down, debris collects, ice forms and the joint between the roof and the chimney stays wet far longer than any other part of the roof. Even good flashing struggles under those conditions.

When a Chimney Cricket Is Typically Required

Whether a cricket is required depends on the chimney width, the roof slope and the code adopted in your jurisdiction. ASHI’s guidance to inspectors states that a cricket or saddle is required by many authorities when the chimney width is more than 30 inches, and its inspection checklist tells inspectors to make sure there is a cricket if the chimney is 30 inches wide or more. That 30-inch figure is a widely used rule of thumb, but local codes, amendments and the edition of the code in force can change the details, including how the cricket must be sized and covered. Front Range jurisdictions do not all adopt the same code edition on the same schedule, so the local building department is the authority for a particular project.

Some practical points about when crickets matter most:

• Wide chimneys. The wider the chimney, the more water and snow collect behind it, and the more a cricket helps. A double-flue masonry chimney or a wide framed chase is a typical candidate.
• Chimneys low on the slope. A chimney near the eave catches runoff from most of the roof above it. A chimney at the ridge sees very little.
• Long, steep slopes above the chimney. Steeper roofs shed snow in larger slabs that can slam into the uphill face.
• Framed chimney chases. Wide wood-framed chases over factory-built fireplaces often need crickets too. Our guide to the chimney chase cover covers the leaks that start at the top of those chases.

Where no cricket is used on a narrower chimney, ASHI describes a back flashing that should extend at least one-sixth of the chimney’s width up the chimney (6 inches minimum) and run up the roof under the shingles to a matching height. That piece is easy to get wrong, which is one reason many roofers favor a small cricket even when it is not strictly required.

Snow, Ice and Colorado Roofs

Snow is where a chimney cricket earns its keep on the Front Range. A Colorado storm can drop heavy, wet spring snow one week and dry powder the next, and the chimney sits right in the path of both. Wind blows snow across the roof and deposits it in the sheltered pocket behind the chimney. Snow sliding down from the ridge piles into the same spot. Then sunny afternoons melt the surface, and nights below freezing turn that meltwater to ice.

FEMA’s Snow Load Safety Guide (FEMA P-957) explains that drifting and sliding snow can create unbalanced snow loads, in which snow accumulates more heavily on one portion of a roof than another. It also notes that when roof drainage is blocked or poorly designed, ice dams may form and reduce the ability of sloped roofs to shed snow. The pocket behind a wide chimney with no cricket is a small-scale version of exactly that problem: a place where snow and ice concentrate and drainage stalls.

The consequences tend to show up in a few ways:

• Water backing up under shingles. When melt cannot drain past a ridge of ice behind the chimney, it can work uphill under shingle laps and reach the underlayment and sheathing. This is the same mechanism behind ice dams at the eaves.
• Concentrated weight. A deep drift behind a chimney adds load to the rafters or trusses in that area. For more on how roofs carry snow, see our guide to roof snow load.
• Freeze-thaw damage to masonry. Brick and mortar that stay saturated through repeated freeze-thaw cycles can spall, crack and lose mortar, which opens more paths for water.
• Flashing damage. Ice and sliding snow can pry at counter flashing and push sealant out of joints, especially where flashing relies on caulk rather than being set into the mortar.

A properly built cricket does not eliminate snow on the roof, but it gives meltwater a sloped path off the back of the chimney and keeps drifts from parking against the masonry for weeks at a time.

Flashing Around a Chimney Cricket

A cricket changes the shape of the roof, but it does not waterproof anything on its own. The flashing where the cricket meets the chimney and where the cricket meets the main roof is what keeps water out. ASHI describes good chimney flashing as two-part: base flashing secured to the roof deck and cap (counter) flashing secured to the masonry. The overlap between them lets the roof and chimney move independently without opening a gap, which matters because a chimney often sits on its own foundation and moves differently from the roof framing.

The pieces involved

• Front (apron) flashing. On the downhill face, a single piece laps over the shingles below the chimney and turns up the masonry.
• Step flashing on the sides. Individual L-shaped pieces are woven into each course of shingles along the sides of the chimney. Our step flashing guide explains why each piece must lap the one below it.
• Cricket flashing. The cricket’s two sloped faces meet the chimney along a diagonal. That intersection needs base flashing turned up the masonry, and the valleys where the cricket meets the main roof need valley treatment similar to a full-size roof valley.
• Counter flashing. Pieces set into the mortar joints (a reglet) and folded down over the base flashing on every side, including behind the cricket.

ASHI cautions inspectors that cap flashing sealed only with caulk or asphalt cement, rather than set into the mortar, should be considered a temporary situation and an ongoing maintenance item. ASHI also notes that rust, incompatible metals (such as aluminum flashing against masonry mortar or steel nails in copper flashing) and tar smeared over metal flashing are common findings around chimneys.

Underlayment matters too

Because the area around a chimney is prone to ice and wind-driven water, many roofers add self-adhered ice barrier membrane over the cricket and around the chimney before shingles and flashing go on. Requirements for ice barrier vary by jurisdiction and climate. Our guide to roof underlayment explains the difference between felt, synthetic underlayment and ice barrier membranes.

Signs of a Missing or Failing Cricket

Problems at the back of a chimney are often visible from a ladder, a drone photo or the attic. Common warning signs include:

• No cricket at all behind a wide chimney, or a cricket that has been removed during a reroof. ASHI includes a photo of a cricket removed from a masonry chimney wider than 30 inches as an example of what inspectors find.
• A cricket that is too small, leaving a flat shelf at either end where water still ponds against the masonry.
• Granule loss, debris buildup or moss in the valleys where the cricket meets the main roof.
• Back flashing sealed with heavy tar, caulk or roof cement instead of proper counter flashing.
• Rusted, loose or lifted flashing, or flashing pulled away from the mortar joints.
• Water stains on the ceiling or walls near the chimney, or stains, damp insulation or dark sheathing in the attic around the chimney opening.
• Deteriorated mortar, spalled brick or white efflorescence on the uphill face of the chimney.
• Soft or sagging sheathing when someone walks the roof near the chimney.

Stains in the attic do not always point to the cricket. The chimney crown, cap, flue tiles or brick itself can also let water in, and our roof leak guide walks through how to narrow down the source. A missing chimney cap lets rain straight down the flue, which can be mistaken for a flashing leak.

Hidden damage under a leaking cricket

Water that gets past the flashing behind a chimney tends to soak into the sheathing and framing around the chimney opening. Over several seasons, that can lead to rot, mold growth on the underside of the roof deck and weakened rafters. EPA’s guidance on mold and moisture notes that drying water-damaged areas within 24 to 48 hours generally prevents mold growth, which is rarely possible with a slow roof leak nobody has noticed. Repairs on an older leak frequently include replacing sections of roof sheathing, not just flashing.

What Home Inspectors Check

The ASHI Standard of Practice requires home inspectors to inspect roofing materials, roof drainage systems, flashing, and skylights, chimneys and roof penetrations, and to describe the methods used to inspect the roofing. Inspectors are not required to inspect the interiors of flues or chimneys that are not readily accessible. In practice, an inspector looking at a chimney will typically:

• Note the chimney width and whether a cricket is present behind it.
• Look for missing flashing pieces, open joints at the top of counter flashing and reliance on sealant.
• Check the valleys and roofing on the cricket itself for wear, debris or damage.
• Look in the attic around the chimney for stains, damp insulation, rot or daylight.
• Note any masonry deterioration that might indicate long-term water exposure.

Many inspectors will not walk steep, wet, icy or fragile roofs and will instead inspect from a ladder, the ground or with a drone. Snow on the roof during a winter inspection can hide the cricket entirely, so a buyer may want to ask for a follow-up look once the roof is clear. A chimney sweep can evaluate the crown, flue and cap from the top at the same visit. For the broader picture of what is included, see our hub on structure and exterior inspections.

Building or Repairing a Chimney Cricket

Adding a cricket is a roofing and carpentry job, usually done when the roof is being replaced, because shingles, underlayment and flashing around the chimney must all be removed and rebuilt. The general sequence looks like this:

1. Remove roofing and flashing around the chimney and inspect the sheathing and framing for rot.
2. Frame the cricket with a ridge board and small rafters or a pre-built plywood saddle, sized to the chimney width and the roof slope.
3. Sheath the cricket and install underlayment, typically including ice barrier membrane in snowy climates.
4. Install base flashing where the cricket meets the chimney and valley treatment where it meets the main roof.
5. Roof the cricket with shingles or sheet metal, then install counter flashing set into the mortar joints.

Some roofers build crickets entirely from sheet metal; others frame them in wood and shingle them. Either can work if the slopes drain and the flashing is sound.

A cricket is not a fix for a chimney that is falling apart. If the crown is cracked, the brick is spalling or the flue liner is damaged, those issues need to be addressed at the same time. Our chimney liner guide covers flue repairs that often come up during the same project.

Permits and who to hire

Roof replacement in most Colorado jurisdictions requires a permit, and adding a cricket during a reroof is usually covered by that permit. Hire a licensed, insured roofing contractor, and ask specifically how the cricket and chimney flashing will be built. A written quote should state whether the cricket is included, what material covers it, whether counter flashing will be cut into the mortar and whether damaged sheathing will be replaced.

Chimney Cricket Costs

Prices vary widely with chimney width, roof pitch, access, roofing material and whether the work is part of a full reroof. As a rough 2026 guide, and not a quote:

• Adding a cricket during a planned roof replacement: often a modest add-on, commonly in the low hundreds to around a thousand dollars, because the roof is already open.
• Retrofitting a cricket on an existing roof: often more, potentially several hundred to a few thousand dollars, since shingles and flashing around the chimney must be removed and rebuilt.
• Sheet-metal crickets or custom metalwork: can cost more depending on the metal and the complexity of the chimney.
• Hidden damage: replacing rotted sheathing or framing, rebuilding mortar or repairing interior ceilings adds to any of these figures.

Get more than one written quote and compare what is included rather than just the total. A cheap job that seals the back of the chimney with roof cement instead of building a cricket may need repeat repairs every season.

If you are buying a home in Colorado with a wide masonry chimney or a framed fireplace chase, ask your inspector to look specifically at the back of the chimney. For more on choosing an inspector and what a full inspection covers, see our guide to hiring a home inspector.

References

• Chimney Flashings — American Society of Home Inspectors
• Snow Load Safety Guide (FEMA P-957) — Federal Emergency Management Agency
• ASHI Standard of Practice for Home Inspections — American Society of Home Inspectors
• A Brief Guide to Mold, Moisture and Your Home — U.S. Environmental Protection Agency

Seeing stains near the chimney or unsure whether that wide chimney has a proper cricket? Reach out to us to schedule a Front Range inspector who checks roofs, flashing and chimneys.