Repair or Replace a Chimney Crown? How to Decide in Pierce County

A proper crown is a slab of concrete or a dense mortar mix formed over the top course of brick, sloped away from the flue and extending past the chimney face so water drips clear. Many older chimneys instead have a thin layer of mortar troweled across the top, often called a wash. It looks like a crown from the ground but is far weaker, and it is often the reason a crown fails early.

The metal cap above it is a separate part. A cap without a sound crown still lets water into the brick, and a new crown with no cap still leaves the flue itself open to rain.

Concrete and mortar fail mostly through water that gets in and freezes. The count of freezing nights differs sharply across the service area. The long-record Tacoma #1 station averaged about 31.8 days a year with a low at or below 32 degrees, most of them in December and January. Down on the Puyallup valley floor, the 2 W experiment station logged about 69, and Buckley 1 NE, the nearest long record to the Bonney Lake plateau, about 60.

Rain adds to it. WeatherSpark gives Puyallup and Bonney Lake a wet season of about seven months, with November averaging roughly 8.3 and 8.6 inches of rain respectively. Bonney Lake also sits at around 574 to 591 feet, well above the shoreline towns, and its snowy period runs from about mid-December to the start of February. A crown there spends more nights cycling between wet and frozen than one near Commencement Bay.

Shaded chimneys under firs and cedars often carry a mat of moss on the crown and top courses. Oregon State University Extension explains that roof moss traps soil and debris that hold moisture, and can lift roofing and let water reach the layers beneath. On a crown, that same mat keeps the surface wet long after rain stops.

Removing the moss is a start, but it grows back where the shade stays. Letting in sun by cutting back the trees that shade the roof is what OSU recommends for lasting results. Its same guide notes that zinc sulfate eats into copper, so keep it away from a chimney trimmed in copper.

The decision follows the depth of the damage. A crown with fine surface cracks and a solid body can be cleaned and coated with a flexible crown sealer. A crown that is sound but rough or thin can sometimes be resurfaced. A crown that is broken through, lifting, crumbling at the edges or built as a flat mortar wash with no overhang is normally rebuilt, because a coating cannot hold together a slab that has already separated.

Crown work is part of our masonry repair, which starts at $425 and is priced from what the roof inspection finds. For fixing a damaged crown in Tacoma, Homeyou estimates $150 to $300; nationally, HomeAdvisor lists crown repair at $150 to $350 and Fixr puts crown replacement at $1,000 to $3,000. We found no South Sound chimney company that publishes a crown price. Those figures belong to their publishers and are not our quote.

The gap between a repair and a replacement in those numbers is the practical argument for catching a crown early. A visit to look at it is $99 plus tax, deducted from the crown work if you give the go-ahead on the written quote.