Chimney crown vs. chimney cap: what's the difference?
People mix these two up all the time. They sit right next to each other on top of the chimney, but they do different jobs, and when either one fails, water gets in.
The crown
The crown is the concrete slab that covers the top of the brick around the flue. It's built with a slope so rain runs off, and an overhang so water drips clear of the brick below. When the crown cracks, water goes straight down into the chimney.
The cap
The cap is the metal cover over the flue opening, usually with a mesh screen around the sides. It keeps rain, animals, leaves and debris out of the flue and helps keep sparks from landing on the roof.
Do you need both?
Yes. The crown protects the masonry, and the cap protects the flue. A chimney with a good cap and a cracked crown still lets water into the brick. A solid crown with no cap still lets rain and animals into the flue.
Signs the crown needs work
- Cracks you can see from the ground or the roof
- Crumbling edges or missing pieces
- White staining on the brick near the top of the chimney
- Flaking brick or open joints in the top few courses
- Water stains on the ceiling near the chimney
Repair or replace?
Small hairline cracks can sometimes be sealed. A crown that's broken up, crumbling or was never sloped properly is usually removed and replaced with a new poured crown. If the brick under it is in bad shape, the top of the chimney may need to be rebuilt first.
Who does what
Crowns, brick and mortar are masonry work. Flue liners, sweeping and inspections inside the flue are a chimney sweep's job. Flashing, where the chimney meets the roof, usually goes with roofing.
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