Water and moisture
Chimney flashing and crickets
The joint where a chimney meets the roof is one of the most common leak points on a house.
Short answer. Flashing is the metal that seals the gap between the chimney and the roof. On a wide chimney, a cricket (also called a saddle) is a small peaked structure behind the chimney that sheds water around it. The International Residential Code calls for a cricket when a chimney is more than 30 inches wide measured parallel to the ridgeline and does not intersect the ridgeline. Your local code and edition may differ.
Flashing: what it is
Flashing is built in two parts that overlap. Step flashing runs up the sides of the chimney, woven into the roof shingles. Counter flashing is set into the masonry above it and folds down over the step flashing. The overlap lets water run off while the chimney and roof move independently.
Crickets and saddles
On the uphill side of a chimney, water running down the roof meets a flat wall and can pool. A cricket is a small ridge built behind the chimney that divides the water and sends it around both sides. The International Residential Code, which model building codes in many states are based on, calls for a cricket where the chimney dimension parallel to the ridgeline is greater than 30 inches and the chimney does not intersect the ridgeline (2021 edition, section R1003.20). Check with your local building department for what applies to you.
Signs flashing is failing
| Sign | Possible cause |
|---|---|
| Stain on ceiling beside the chimney | Gap in flashing or failed sealant |
| Rust on flashing | Aging metal |
| Sealant cracked or peeling | Exposure and age |
| Water pooling behind the chimney | No cricket or a clogged one |
Repair or replace?
Resealing can buy time when the metal is sound. Replacing is the better route when the metal is corroded or has been resealed repeatedly. See chimney flashing repair and Why is water coming into my chimney?.
Signs checklist
- Stains on the ceiling or wall near the chimney.
- Gaps or lifted metal where the chimney meets the roof.
- Dried sealant that has cracked or peeled.
- Water collecting behind a wide chimney.
- Rust on the flashing.
Common misconceptions
"Sealant alone is a lasting fix." It is often temporary on a joint that moves.
"A cricket is optional." Wide chimneys can pond water without one.
Sources
- International Code Council, 2021 International Residential Code, Chapter 10, section R1003.20 Chimney crickets (the edition and amendments adopted in your town may differ)
About this guide. Published by Dr. Sweeper as general homeowner education, last updated October 1, 2026. Sources are linked where they are cited. What applies to your home can depend on your local building code, your appliance and its manufacturer's instructions, and the actual condition of your chimney, so this guide is not a substitute for an inspection.
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