Chimney Crown Repair and Replacement

A crown takes more rain than any other part of the chimney because it faces straight up. Many old crowns were never real crowns at all, just a thin wash of mortar troweled over the top bricks. That wash cracks, water gets under it and freezes, and the cracks widen every winter. Sea-Tac averages about 25 nights at or below freezing a year, and Renton and Boeing Field see closer to 30.

A crack in the crown is easy to miss from the ground, yet it often explains a leak at the fireplace or a wet stain on the ceiling. We check the crown at every free inspection and photograph what we find. Then we tell you plainly whether it can be sealed or needs to be replaced, because sealing a crown that is already broken through only delays the same repair by a winter or two, and the brick under it keeps taking water in the meantime.

Signs you need this

• Cracks in the concrete or mortar on top of the chimney
• Pieces of the crown on the roof or in the gutter
• Water dripping onto the damper or into the firebox
• Damaged brick at the very top courses of the chimney
• A crown that sits flush with the brick, with no overhang

How we do it

1. Inspect the topWe check the crown for cracks, gaps around the flue tiles and whether it sheds water past the brick.
2. Seal or replaceFine cracks get a flexible crown sealer; a broken or poorly built crown is removed.
3. Pour a new crownA replacement crown is formed and poured with a slope and an overhang so water drips clear of the brick.
4. Leave a gap at the flueA small flexible joint around the flue tile lets it expand without cracking the new crown.

What is the difference between sealing and replacing a crown?

If the crown is solid and well shaped with only hairline cracks, a flexible crown sealer brushed over it can keep water out for years. That is the cheaper route, typically $600 to $1,000.

If the crown is broken through, crumbling or just a thin mortar wash, sealing will not hold. A new poured crown, built thick enough, sloped and with an overhang, is typically $1,000 to $2,200 depending on the chimney's size and how many flues pass through it.

Why does moss matter on a crown?

Moss needs shade and moisture, and the top of a chimney under a big fir or cedar gets plenty of both. Oregon State University Extension notes that moss holds moisture against roof surfaces and extends the time they stay wet. A crown that stays wet longer gives water more time to work into every crack.

We clear moss from the crown when we work on it. Do not pressure wash it, which OSU Extension also warns can damage roofing, and remember that zinc moss products corrode copper flashing.

Does a cap protect the crown?

A cap keeps rain out of the flue, and a wide cap that covers the whole top also shields much of the crown. It is not a substitute for a sound crown, but the two together keep the top of the chimney much drier.

A cap is typically $250 to $850 if you add one at the same time.