What is a chimney crown?
Updated August 2026
A chimney crown is the sloped slab of concrete or mortar across the top of a masonry chimney that throws rain clear of the brick below. Built properly, it is cast concrete, 3 to 4 inches thick at the flue, sloped to the edges, overhanging the brick by about 2 inches, with a drip groove cut underneath. Many chimneys instead got a mortar wash, a thin skim the mason troweled on at the end of the job, and those begin cracking within 5 to 15 years.
Where it is
Stand back on the lawn with binoculars and look at the very top of the stack. The crown is the flat gray surface surrounding the clay flue tiles that poke up out of it. Do not confuse it with the chimney cap, which is the small metal lid and screen sitting over the flue opening itself: the crown is horizontal and structural, the cap is a hat. Because you can only really see a crown from a roof or a drone, most homeowners meet theirs in a sweep's inspection photos. The ground-level clue is debris, sand-colored grit and mortar chunks collecting in the gutter below the chimney, or white efflorescence staining down the brick.
What it does
The crown seals the gap between the flue liner and the surrounding brick, the widest opening anywhere on the chimney. Once it cracks, rain runs straight into the core of the stack, and the damage compounds every winter: absorbed water freezes, expands about 9 percent, and pops the faces off bricks, a process called spalling. The same water rusts the damper shut, dissolves mortar joints from the inside, and eventually reaches the living space as a ring stain on the ceiling around the chimney chase or a musty, sooty smell after heavy rain. A hairline crack is a $200 problem the year you find it and a $3,000 masonry job eight winters later.
Maintenance
Have the crown looked at during the annual chimney inspection, which is the same visit as the sweep and adds nothing to the bill. Hairline cracks under roughly 1/8 inch take a brushed-on elastomeric crown coat: $40 to $70 a pail if you are comfortable on a roof, $150 to $400 for a sweep to do it, and it holds 8 to 12 years. Anything wider, crumbling, or missing its overhang needs a new crown poured. Keep this on the same yearly rhythm as the rest of the chimney checklist, because water damage caught in year one is a sealant job and water damage caught in year six is masonry work.
What it costs to replace
A replacement chimney crown runs $800–2,500 to cast a new one, while sealing an intact crown is $150–400.
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Frequently asked questions
What is the difference between a chimney crown and a chimney cap?
The crown is the concrete slab covering the whole top of the masonry, sloped to shed water off the brick. The cap is the metal lid with mesh sides that sits over the flue opening to keep rain, birds, and embers out of the flue itself. A chimney needs both. A cap costs $150 to $400 installed and can be added any time; a crown is part of the structure and gets replaced only when it fails.
Can I seal a cracked chimney crown myself?
If the cracks are hairline and you are steady on a steep roof, yes. Wire-brush the surface, fill anything wider than a pencil line with mortar repair caulk, then roll or brush two coats of flexible crown sealer across the whole slab and 1/2 inch up the flue tiles. Materials run $40 to $70. Skip it when the crown is crumbling, missing chunks, or sits above a second story: sealer over failed concrete only hides the problem for a season.
How long does a chimney crown last?
A cast concrete crown with reinforcement, real slope, and a 2-inch overhang lasts 30 to 50 years and often outlives the roof under it. The thin mortar wash used on a lot of 1960s through 1990s chimneys cracks in 5 to 15 years, because mortar shrinks, carries no steel, and usually got poured flush to the brick with no drip edge. Resealing every 8 to 12 years roughly doubles what either version survives.