How Often Should You Replace a Chimney Cap in Redmond, WA?

NFPA 211, the national chimney standard, asks for a look at each chimney, fireplace and vent once every year; CSIA, the sweep certification body, passes that wording on to homeowners. The cap is the first thing a technician sees from the roof, so it gets looked at on that same visit. A cap that is tight, square, unrusted and clear of debris stays. One that fails any of those four tests gets repaired or replaced.

That is a less satisfying answer than a number, but it is the accurate one. Two caps installed the same week on the same street can end up in very different shape, depending on the metal, the trees overhead and whether the roof faces the weather.

Start with rain. On WeatherSpark's long-term averages, Redmond's wetter season starts October 9, ends May 2 and so covers some 6.8 months. November is the peak, with around 8.7 inches of rain spread over 17 to 18 wet days. A cap spends most of that stretch damp, and damp steel with a scratched or thin coating rusts.

Then wind. The same source gives Redmond a windier period of about 5.9 months, from mid-October to mid-April, with the wind coming mostly from the south. The Western Regional Climate Center adds that across western Washington late fall and winter bring the strongest winds, generally out of the south or southwest. The city's own hazard plan describes a hill-and-valley terrain that funnels wind in several places, and it singles out the steep slopes of Education Hill as likely to take the worst of a severe storm. The same plan looks back at the windstorm of December 2018, when gusts reached 45 mph. A cap held by four small screws into a clay flue tile, or by a pressure band that was never retightened, is the one that ends up in the yard after a night like that.

Trees are the third factor. Next door in Sammamish, the city's hazard plan says 48 percent of the land is under tree canopy and that winter storms regularly bring down limbs. Any Redmond roof with tall firs or maples above it is exposed in the same way. A limb does not need to be large to bend a cap lid or tear the mesh, and needles and leaves that pile against the screen hold water on the metal long after the rain stops.

Farther east the rain increases. WeatherSpark's November average is about 9.5 inches for Duvall and 9.8 inches for Carnation, where the wet season runs about 7.3 months. Caps in the valley simply get more wet days per year than caps in town.

The metal decides how the cap fails. This table is general trade knowledge, not a warranty statement; a manufacturer's own warranty tells you what that product is expected to do.

Rust trails on the crown or down the brick. By the time rust is running, the coating is gone and the metal is thinning. The stain is also iron-rich water soaking into the masonry.

A lid that has shifted or lifted. If the cap sits crooked or rattles in wind, the attachment has failed. The next strong southerly can take it off entirely, and a flue with no lid lets rain fall directly on the smoke shelf and the damper.

Torn or missing mesh. Birds and squirrels look for exactly this kind of opening in spring. Where a spark arrestor is installed, the Washington residential code is specific: the openings must not let a half-inch sphere through, must not be so fine that a three-eighths-inch sphere is blocked, and the screen's net open area must equal the flue outlet's area four times over, or more. Mesh patched with hardware cloth from the garage rarely meets that.

Mesh blocked with soot or creosote. This is a draft problem before it is a cap problem, and it usually means the flue is due for a sweep. A screen that clogs again and again may be too fine for the appliance.

Water or debris in the firebox. Drips on the hearth after rain, twigs on the damper or a musty smell can each point to a cap that has stopped doing its job, though the crown and the flashing need to be ruled out as well.

People often use one word for all three, and that can lead to buying the wrong repair. The cap is the metal hood over the flue opening. The crown is the sloped masonry or concrete slab that closes the top of a brick chimney around the flue. The 2021 Washington State Residential Code, which the City of Redmond has enforced since March 15, 2024, requires that top to be concrete, metal or stone, sloped so water runs off, with a drip edge and a caulked gap around the flue liner. A chase cover is the sheet-metal pan on top of a framed, sided chimney around a factory-built fireplace.

A new cap on a cracked crown solves half the problem. If the inspection finds both, the quote lists them as two lines, so the role of each repair is visible.

A chimney cap installed by us is $235 to $850. The spread comes from the size of the cap, from how many flues it has to cover and from whether it must be custom made. We do not price a cap from a photo taken on the lawn, because the flue has to be measured and the crown checked.

It starts with a technician on the roof: the inspection visit is billed $99 plus tax, and the $99 is deducted from the written quote the day you accept it. Late summer is the easy time to book: the roof is dry, and the cap is on before the October rain returns.