Chimney Crown Repair and Replacement in the Twin Cities

The crown takes the weather head-on. Snow sits on it, ice forms in its cracks, and a Twin Cities winter offers about 75 freeze-thaw days at MSP and roughly 90 in the north metro, by our arithmetic on NOAA normals. Many older crowns were never built right in the first place: a thin layer of mortar troweled flat over the top course, with no overhang. Water sits, soaks in and freezes.

The current Minnesota Residential Code adopts IRC R1003.9.1, which says a masonry chimney shall have a concrete, metal or stone cap, sloped to shed water, with a drip edge and a caulked bond break around any flue liners. Those details are what we build to. Small crown cracks are typically repaired for $200 to $700+, and a new crown with a drip edge runs $1,000 to $3,000.

Signs you need this

• Cracks across the top of the chimney you can see from a ladder or photo
• Chunks of concrete or mortar on the roof
• Water in the firebox or rust on the damper after rain
• Spalling or open joints on the top few rows of brick
• A flat top with no overhang beyond the brick

How we do it

1. Free inspectionWe check the crown, the brick under it and the flue tile where it passes through.
2. Repair or replaceHairline cracks in a sound crown can be sealed; a crumbling or flat crown is replaced.
3. Build it properlyA new crown is formed with a slope, an overhang and a drip edge so water falls clear of the brick.
4. Bond break at the linerA gap at the flue tile is filled with a flexible sealant so the liner and crown can move independently.
5. Cap if neededWe recommend a cap on top to keep snow and rain off the crown and flue.

What makes a crown last

• Sloped to shed water, as IRC R1003.9.1 requires
• A drip edge so water falls clear of the brick face
• Enough thickness to resist cracking
• A caulked bond break around the flue liner
• A cap above it to keep snow and rain off

Crown versus cap

The terms get mixed up. In code language, the IRC calls the concrete top a chimney cap, and in everyday trade language it is the crown. The metal cover with mesh sides that sits on top of the flue is what most people mean by a chimney cap. A good chimney has both.

Seasonal timing

Concrete needs warm enough weather to cure. We build new crowns from spring through fall. In winter, if a crown has failed badly, we can put on a temporary cover to slow water entry until the weather turns.