A wide chimney acting as a wall against downward-flowing water will trap moisture and debris, causing severe leaks. To prevent this, building codes mandate a Chimney Cricket (also called a saddle)—a small, custom-framed peaked roof built directly behind the chimney to divert water safely around its sides. The International Residential Code (IRC) strictly requires a cricket for any chimney wider than 30 inches. If your current roof lacks one, the contractor must frame it during the replacement, generating a mandatory change order typically ranging from $350 to $650.
During a heavy rainstorm, thousands of gallons of water cascade down the slope of your roof. If a massive brick structure is sitting directly in the middle of that slope, it acts exactly like a concrete dam on a river.
When a roof tears off, the decking behind the chimney is frequently found to be completely rotten. This is a forensic indicator of a missing roof cricket. Modern roofing estimates must legally include the cost of constructing this aerodynamic diverter if your chimney’s dimensions trigger the code requirement.
Hydrodynamics: The “Dam Effect”
Without a cricket, the flat space directly behind the chimney (known as the “back pan”) becomes a trap. Over the course of a single year, the physics of the roof slope cause severe stress to this area:
- Hydrostatic Pooling: Water rushes down the slope and hits the flat back of the brick. Unable to move laterally fast enough, the water pools up, submerging the metal flashing.
- Debris Accumulation: Pine needles, leaves, and twigs wash down the roof and get trapped against the flat back of the chimney. This organic debris acts like a sponge, holding moisture against the brick and flashing for weeks after a rainstorm.
- Ice Expansion: In winter climates, the pooling water freezes. As it turns to ice, it expands, physically prying the metal flashing away from the brick mortar, instantly breaking the waterproof seal.
A cricket solves all three of these issues simultaneously. By framing a miniature “A-frame” roof behind the chimney, the water hits the peak of the cricket and is immediately diverted to the left and right, sliding safely down the sides of the chimney without ever pooling.
The 30-Inch Legal Mandate (IRC R905.2.8.3)
Many older homes were built without crickets to save on framing costs. Today, building inspectors strictly enforce the laws regarding chimney hydrodynamics. According to the International Residential Code (IRC):
“A cricket or saddle shall be installed on the ridge side of any chimney or penetration more than 30 inches wide as measured perpendicular to the slope.”
If your chimney is 31 inches wide and currently lacks a cricket, your roofing contractor is legally obligated to construct one before they can install the new shingles. This involves a carpenter cutting 2×4 framing lumber, anchoring it to the roof deck, covering it with OSB plywood, wrapping it in Ice and Water Shield, and custom-flashing the valleys it creates.
Chimney Cricket Framing Estimator
Input your chimney width to determine if a cricket is legally required, and estimate the change order cost to frame and flash the structure.
Framing a proper cricket takes time, lumber, and specialized carpentry skills. Lazy or low-budget roofers often bypass the 30-inch code mandate by building a “Tar Cricket.”
Instead of framing a wooden peak, they smear a massive, sloped mound of black roofing cement (tar) directly against the back of the chimney to force water around it. Within 24 months, the UV rays from the sun will bake the tar, causing it to shrink, crack, and pull away from the brick. Water will pour directly into the resulting fissure. A cricket must be structurally framed with wood and flashed with metal; roof cement is not a structural material.
Eliminate Forensic Surprises
Do not wait until the roof is torn off to negotiate custom carpentry prices. Our 40-Factor Estimator uses your chimney’s dimensions to pre-calculate the required framing costs for Code-Compliant crickets.
Launch the 40-Factor Estimator →Frequently Asked Questions
Does a 24-inch wide chimney need a cricket?
By the letter of the IRC code, no. A standard flat back-pan flashing is legally acceptable for penetrations under 30 inches. However, highly skilled roofers will often recommend framing a small cricket anyway, especially if the home is located in a heavily wooded area where debris accumulation is a chronic problem.
Should a cricket be shingled or covered in metal?
Both are acceptable. A standard cricket is framed in wood, covered in Ice and Water Shield, and then shingled to match the rest of the roof. However, an ultra-premium installation involves covering the entire framed cricket in a single, seamless piece of custom-soldered metal (like copper or galvanized steel). This eliminates all seams and creates a bulletproof water diverter.
Structural & Code References
- International Residential Code (IRC): Section R905.2.8.3 – Crickets and saddles, specifically dictating the 30-inch width mandate perpendicular to the roof slope.
- Sheet Metal and Air Conditioning Contractors’ National Association (SMACNA): Architectural Sheet Metal Manual guidelines for structural saddles and back-pan flashing dimensions.