What are Diablo winds and do they matter for a chimney?

Offshore winds that blow hot and dry from the interior toward the coast, typically in autumn, and they drive the county's highest fire danger. For a chimney they matter in two ways: ember transport from an unscreened flue is a genuine risk during those conditions, and strong winds cause downdraft problems in flues that are marginal to begin with.

Is spark arrestor screening required here?

Yes, for every chimney serving a wood-burning appliance, under the state building and residential codes. It matters most in the county's elevated fire hazard severity zones, and a good deal of the hillside property falls into those zones. The requirement specifies screening with a maximum opening size, which a decorative cap does not necessarily provide.

We get smoke blowing back into the room on windy days. Is that a blockage?

Not necessarily. Wind-driven downdraft is a common cause, particularly during Diablo conditions, and it is a different problem from a restricted flue. Height, termination position relative to the roofline and surrounding structures all affect it. Worth establishing which it is before paying for a cleaning that may not change anything.

Bay Area · 1,165,927 residents (2020 Census)

Chimney Services in Contra Costa County

Hotter summers and colder winters than the rest of the Bay Area, serious wind exposure, and a lot of hillside property in fire terrain.

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Chimney & Fireplace

Sweeping, inspection and repair

Wood, Gas & Factory-Built

Different systems, different work

Inspection Is Separate

Not bundled into a cleaning

California Service Areas

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Contra Costa sits behind the coastal hills, and that geography gives it a more continental climate than the counties to its west — genuinely hot summers, genuinely cold winter nights, and a wider annual swing through which masonry has to move. Fireplaces here get used more than in San Francisco or Oakland. The county also carries substantial hillside and wildland-interface property, and the Diablo wind events that drive autumn fire risk across Northern California are named for the mountain in the middle of it.

What matters about Contra Costa chimneys

Sheltered from marine influence by the coastal hills, the county experiences a substantially wider annual temperature range than the western Bay Area, driving faster mortar joint deterioration.
Diablo wind events through autumn produce the county's highest fire danger conditions, and hillside communities sit in elevated fire hazard severity zones, where the spark arrestor required on every wood-burning chimney matters most.
Source: CAL FIRE
Higher burn intensity than the coastal Bay Area counties means flue deposits accumulate faster here than in San Francisco or Oakland despite sharing the same air district rules.
Homes built in Contra Costa County since November 1, 2016 cannot include a wood-burning fireplace or stove under Bay Area Air Quality Management District Regulation 6, Rule 3, and older ones fall under the district's winter Spare the Air no-burn alerts.
Source: BAAQMD
Post-war suburban development through the 1950s to 1980s dominates the central county, with masonry fireboxes and clay tile liners now well into middle age.

West, Central, Lamorinda and East County

Contra Costa is four different housing markets. Richmond, on the bay in the west county, grew fast around the World War II shipyards and has older housing with more marine damp than the rest of the county. Central county, Concord, Walnut Creek, Pleasant Hill and Martinez, is mostly post-war suburbs with masonry fireplaces now well into middle age; The Concord page covers that housing in detail.

Lafayette, Danville and San Ramon run up into the hills, where fire hazard severity zones and Diablo winds make the spark arrestor and the cap the priority. Antioch and Brentwood in the east county grew mostly from the 1990s onward, so more of their fireplaces are factory-built or gas, and any home built since November 1, 2016 has no wood-burning fireplace at all under the air district's rules.

Nineteen Cities, One Air District

The county has nineteen incorporated cities, each issuing its own building permits, plus unincorporated areas permitted by the county. Which office issues a permit for an installation or rebuild depends on the exact address, not the ZIP code.

The burn rules are simpler. All of Contra Costa is under the Bay Area Air Quality Management District, so Spare the Air alerts apply in Brentwood exactly as they do in Richmond.

Cities in Contra Costa County

Concord

125,410 residents (2020 Census)

Other cities we serve in Contra Costa

Richmond · Antioch · San Ramon · Walnut Creek · Danville · Lafayette · Martinez · Pleasant Hill · Brentwood

Nearby counties

Alameda County Sacramento County

Contra Costa County — common questions

Because the climate behind the hills is genuinely different. Contra Costa winter nights run colder than the marine-moderated western Bay Area, so fireplaces here do more work. The practical consequence is that deposits accumulate faster, even though the same Spare the Air restrictions apply to both.

Not sure which service you need?

Tell us what the chimney or fireplace is actually doing and we will tell you which service applies — including when the answer is that you do not need one yet.

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