A chimney leaking at the roof line is usually a flashing problem: missing or rusted step flashing along the sides, counterflashing that was caulked to the brick instead of set into the mortar joints, or no cricket behind a wide chimney so water and snow pile up against it. Less often the water comes through a cracked crown or porous brick above the roof. The fix is new metal installed in layers, not more sealant. This page is general information; your roofer and building department decide what your home needs.
On this page: Signs · Causes · Ground checks · Repairs · Code basis · When to call
Signs of a chimney leak
- Stains on the ceiling or wall right beside the chimney.
- Wet or darkened framing around the chimney chase, seen from the attic.
- White, chalky deposits (efflorescence) on interior brick.
- Water in the firebox or dripping down the flue, which points higher up, to the crown or cap.
- Ice or a pile of debris on the uphill side of the chimney after storms.
What goes wrong at a chimney
A chimney needs two layers of metal. Step flashing is woven into each shingle course and turns up the brick. Counterflashing is cut into the mortar joints and laps down over the step flashing, so water running down the brick lands on the roof instead of behind the metal. Common failures:
- Step flashing with no counterflashing, or counterflashing glued to the brick face with caulk.
- A continuous cut sawn straight through the bricks parallel to the roof instead of stepped cuts in the mortar joints.
- Old flashing reused on a new roof and rusted through.
- No cricket behind a wide chimney, so water and snow sit against the back.
- A cracked or flat crown (the cap on top of the masonry) letting water into the brick.
What you can check from the ground
Use binoculars; do not climb up. Look for:
- Sealant-only joints where metal meets brick, or tar slathered across the base.
- Loose, bent or missing counterflashing on any side.
- A peaked saddle behind the chimney. If the chimney is wide and does not reach the ridge, there should be one.
- The crown and cap. Cracks, crumbling top courses or a missing rain cap.
Then note when the leak shows up: any rain, wind-driven rain only, or snowmelt. That pattern saves time during the inspection.
How a chimney leak is fixed
| Repair | When it fits |
|---|---|
| Reset loose counterflashing in the mortar joints | Metal is sound, but a piece has pulled out. |
| New base, step and regleted counterflashing | Flashing is rusted, caulk-only or missing. This is the most common real fix. |
| Build and flash a cricket | The chimney is more than 30 inches wide on the ridge side and has none. |
| Rebuild the crown with a sloped cap and drip edge | Crown cracked through or flat. |
Fixes that fail: caulk-only counterflashing, a continuous reglet sawn through the brick, roof cement spread over the whole base, a sealant fillet behind the chimney in place of a cricket, and roof cement troweled over a cracked crown.
Code and industry basis
- Flashing. The 2024 IRC, section R905.2.8.4, has chimney flashing applied following the shingle manufacturer’s instructions. Owens Corning’s Duration instructions call for corrosion-resistant step flashing at least 4 by 4 by 8 inches and 2 inches wider than the shingle exposure where the roof meets a chimney or sidewall.
- Counterflashing. An NRCA Professional Roofing article on regleted counterflashing recommends stepped reglets in the horizontal mortar joints, about 2 to 2.5 inches deep in mass masonry (1.75 to 2 inches is often more practical), lead wedges, and mortar fill, because sealant can trap moisture in the wall. It advises against cutting a continuous reglet through the brick.
- Cricket. The 2024 IRC, section R903.2.2, requires a cricket or saddle on the ridge side of any chimney or penetration more than 30 inches wide. The 2021 IRC, section R1003.20, sets cricket height by roof slope, from one-half of the chimney width at 12:12 down to one-eighth at 3:12.
- Crown. The 2021 IRC, section R1003.9.1, calls for a concrete, metal or stone chimney cap sloped to shed water, with a drip edge and a caulked bond break around the flue liner per ASTM C1283.
- Reroofing. IRC section R908.5 requires rusted, damaged or deteriorated flashings to be replaced when the roof is replaced.
Local editions and amendments vary; your building department has the final word.
When to call a roofer
Call at the first stain beside a chimney. Water that gets behind flashing soaks framing for a long time before it shows inside. If the crown or brick is the problem (see cracked chimney crowns), we will say so and point you to a masonry or chimney professional rather than sell a roof repair that will not stop the water. For other leak points, see pipe boot leaks, skylight leaks and valley leaks, or browse the roof problems guide.
Have your chimney flashing inspected
Integrity Roofing and Painting is veteran-owned and family-run since 1990, an Owens Corning Platinum Preferred contractor with 650+ Google reviews. We document each side of the chimney with photos so you can see what failed. Colorado Springs area: (719) 488-2800 or a free inspection. Denver metro: (303) 209-0152 or a free Denver inspection. Austin: (512) 610-5897 or a free Austin inspection. We respond the same business day.
Sources: 2024 IRC Chapter 9, sections R903.2.2, R905.2.8.4 and R908.5 (UpCodes); 2021 IRC Chapter 10, sections R1003.9.1 and R1003.20 (UpCodes); Professional Roofing (NRCA), Anatomy of a regleted counterflashing (2022); Professional Roofing (NRCA), Reroofing by the book (2019); Owens Corning Duration installation instructions.
