Chimney Cricket Saddle Flashing Install

Why this matters

A chimney that interrupts a sloped roof creates a dam on the uphill side. Water, ice, and debris pile against the chimney and find their way through any compromise in the flashing. The IRC requires a cricket (also called a saddle) on the uphill side of any chimney wider than 30 inches measured perpendicular to the roof slope. The chimney sweep called for a flashing leak who finds no cricket on a 36-inch chimney is looking at a code violation and a re-roof, not a flashing patch. This article gives the IRC trigger, the geometry, and the flashing assembly that solves the leak permanently.

IRC requirement and trigger

IRC Section R1003.20 (Chimney Crickets / Saddles) states: chimneys more than 30 inches wide, measured perpendicular to the slope of the roof, shall be provided with a cricket or saddle. The cricket must be covered with sheet metal or with the same material as the roof covering, and constructed to direct water around both sides of the chimney.

A 24-inch chimney does not require a cricket; a 32-inch chimney does. The 30-inch line is measured at the chimney exterior, not at the flue.

Cricket geometry

A cricket is a small ridge that runs from the high (uphill) face of the chimney up to a peak. The geometry directs water laterally around both sides of the chimney rather than damming against the uphill face.

Standard design parameters:

1. Cricket ridge runs perpendicular to the roof ridge.
2. Length from the chimney to the cricket peak is typically equal to half the chimney width. A 36-inch chimney gets an 18-inch cricket; a 60-inch chimney gets a 30-inch cricket.
3. Cricket slope is typically equal to or steeper than the main roof slope, so water sheds rather than pools.
4. Cricket pitch from the chimney face up to the peak must clear the chimney back wall by at least 1 inch to allow flashing tuck.
5. Valleys on each side of the cricket carry water down to the main roof plane.

Materials

The cricket structure: dimensional lumber framing (2x4 or 2x6 hip rafters meeting at a center peak) sheathed with the same plywood or OSB as the main roof. Larger crickets on steep roofs may use 2x6 or 2x8 framing for adequate rigidity.

The cricket covering options:

1. Same roofing material as the main roof (asphalt shingles, metal panels, tile) - typical for smaller crickets that fit within standard shingle dimensions.
2. Sheet metal (typically 26 or 24-gauge galvanized or copper) - required when the cricket is small enough that the roof material would not lap correctly across the ridge.
3. Membrane - on flat or low-slope roof applications, the cricket is covered with the same membrane as the main roof.

Flashing assembly

The chimney-flashing assembly with a cricket has four components per face:

1. Base flashing - L-shaped sheet metal turned up the chimney wall and out onto the roof. Step flashing is used on side walls; continuous flashing is used on the uphill and downhill walls.
2. Step flashing - one piece per shingle course on side walls, woven into the shingle field so each piece covers the joint of the course below.
3. Counter flashing - tucked into a saw-cut reglet in the masonry mortar joint, bent down to cover the top edge of the base flashing. Sealed with high-temperature flexible sealant.
4. Cricket flashing - sheet metal lapped over the cricket ridge and tucked under the counter flashing on the uphill chimney face.

Lap orientation: water flows downhill across each lap. Counter flashing covers base; base covers shingle; cricket flashing tucks under counter and laps over the cricket sheathing.

Step-by-step install sequence

1. Remove the existing flashing and roofing material in a working area extending 18 inches around the chimney on all sides.
2. Inspect the deck and the chimney masonry for water damage; repair or replace deteriorated sheathing before continuing.
3. Frame the cricket - install hip rafters from the chimney to a center ridge, sheath with 1/2-inch or 5/8-inch plywood matching the main roof.
4. Install ice-and-water shield (self-adhering bitumen membrane) over the cricket sheathing and extending at least 24 inches onto the main roof on each side. The membrane is the second-line defense if the flashing or roof covering ever fails.
5. Install the downhill apron flashing first - bent up the downhill chimney face, out onto the roof.
6. Install side step flashings - one piece per course, woven into the shingles.
7. Install the cricket sheet metal - bent over the cricket ridge, with side wings extending onto the main roof and uphill leg up the chimney face.
8. Cut a reglet in the chimney mortar joint about 1 inch above the top edge of all base flashings (uphill, downhill, side step).
9. Install counter flashing into the reglet, bent down to cover the base flashing top edge. Seal the reglet with high-temperature urethane or polyurethane sealant rated for masonry.
10. Reinstall roofing material around the new flashings, tucking each piece under the appropriate flashing leg.
11. Inspect for any gap, daylight, or unsealed lap before closing the job.

Counter-flashing detail at the cricket peak

The cricket peak meets the chimney face at a single point. Counter flashing at this point gets folded around the peak in a wrap-and-tuck detail:

1. Cut the counter flashing wide enough to extend 6 inches beyond the cricket on each side.
2. Bend the center over the cricket peak.
3. Tuck the side wings into reglets on the chimney face on both sides.
4. Seal all reglets and the peak fold.

A flat-cut counter flashing at the peak leaves an open joint that leaks within one freeze-thaw cycle.

Saddle vs. cricket terminology

The two terms are used interchangeably in residential practice. "Saddle" emphasizes the shape (it sits like a saddle on the back of the chimney); "cricket" is the more common term in modern codes. The IRC uses "cricket / saddle" together.

When to call in a roofer

A chimney sweep can install a cricket and flashing competently when the roof material is asphalt shingle and access is straightforward. Three configurations where bringing in a licensed roofer is the right call:

1. Tile or slate roof - removal and reinstallation requires specialty tools and matching tile.
2. Metal roof - panel removal and refit interacts with the panel manufacturer's warranty.
3. Steep roofs above 8:12 pitch - fall-protection requirements and the work-position challenge favor a roofer with the right gear.

References

1. International Residential Code (IRC) Section R1003.20 - Chimney Crickets.
2. NFPA 211 - Standard for Chimneys, Fireplaces, Vents, and Solid Fuel-Burning Appliances.
3. ASTM E2112 - Standard Practice for Installation of Exterior Windows, Doors and Skylights (referenced for flashing best practice).
4. NRCA - National Roofing Contractors Association, Roofing Manual.
5. CSIA - Chimney Safety Institute of America Best Practices for Flashing and Crown Repair.