A cracked chimney crown is the concrete or mortar cap on top of a masonry chimney that has cracked, crumbled or was never built to shed water. Water then soaks into the brick and flue and appears as stains beside the chimney, water in the firebox or spalled brick, and it is often mistaken for a roof flashing leak. The code calls for a sloped cap of concrete, metal or stone with a drip edge and a bond break at the flue liner. Hairline cracks can sometimes be sealed; a cracked-through or flat crown is rebuilt. This page is general information; your roofer, chimney professional and building department make the final call.
On this page: Signs · Causes · What to check · Repairs · Code basis · When to call
Signs of a failing crown
- Water in the firebox or running down the inside of the flue.
- Stains on the ceiling or wall beside the chimney that do not match roof-line leaks.
- Spalled, flaking or crumbling brick near the top of the chimney.
- White mineral deposits (efflorescence) on interior masonry.
- Cracks or missing pieces on the crown, visible with binoculars.
Why crowns crack
- Mortar wash instead of a crown. A thin mortar layer troweled across the top cracks quickly.
- No slope. Flat tops hold water and snow.
- No drip edge. Water runs off the edge and down the brick face instead of falling clear.
- No bond break around the flue liner, so the crown and liner crack as they move at different rates.
- Freeze and thaw. Water in small cracks freezes, expands and widens them every winter.
What you can see from the ground
- Use binoculars on the top of the chimney: look for cracks, missing chunks, and whether the crown overhangs the brick.
- Look for a rain cap over the flue, and whether it is intact.
- Check the top courses of brick for crumbling or flaking.
- Inside, check the firebox and damper area after rain.
Do not climb onto the roof to reach the chimney top. Ladders on steep roofs near chimneys are a common source of falls.
Repairs
| Repair | When it fits |
|---|---|
| Seal fine hairline cracks with a product made for chimney crowns | Sloped, sound crown with surface cracks |
| Replace the crown with a sloped cap that overhangs, has a drip edge and a bond break at the liner | Crown cracked through, flat or crumbling |
| Add or replace the rain cap | Flue open to rain and debris |
| Rebuild the top courses of brick | Masonry is spalling at the top |
| Reflash at the roof line | Flashing is also failing; see chimney flashing leaks |
Fixes that fail: roofing cement smeared over the crown, another mortar wash on top of the old one, and sealing the brick face while the crown still lets water in.
Code basis
The 2021 IRC (Colorado viewer), section R1003.9.1, says masonry chimneys need a cap of concrete, metal or stone, sloped to shed water, with a drip edge and a caulked bond break around any flue liners installed per ASTM C1283. Section R1003.9.3 requires the free area under a rain cap to be at least four times the net free area of the flue outlet. Section R1003.20 covers the cricket required behind wide chimneys; that and roof-line flashing are on our chimney flashing page.
When to call
Call when water appears in the firebox, when brick near the top is flaking, or when a chimney leak keeps coming back after flashing work. A crown rebuild is masonry work. We will tell you whether the water is coming from the crown, the flashing or both, and handle the roof side. The roof problems guide lists related problems.
Have us trace the chimney leak
Integrity Roofing and Painting is veteran-owned and family-run since 1990, an Owens Corning Platinum Preferred contractor with 650+ Google reviews. We photograph the crown, cap and flashing so you can see where water is getting in. 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. Same-business-day reply.
Sources: 2021 IRC Chapter 10, sections R1003.9.1, R1003.9.3 and R1003.20 (UpCodes, Colorado viewer).
