Contra Costa County, CA Noise Ordinances: Quiet Hours (2026)

The county's own Department of Conservation and Development (DCD) said it in writing on June 14, 2024, in a memo to every Municipal Advisory Council: "the County's regulations are not comprehensive and there are gaps in coverage." There is no decibel limit, no 10 p.m. cutoff and no "plainly audible" test for ordinary residential noise anywhere in the Ordinance Code, Division 54 (Public Order) covers curfew, social-host liability, alarm systems and open containers, and nothing on noise. What the county does regulate is narrower: the Temporary Events Ordinance, Chapter 82-44 (Ord. 2005-25, last amended by Ord. 2024-07 on March 5, 2024), which reaches outdoor gatherings of more than 75 people in a residential or agricultural district or at any residence, and more than 150 people elsewhere; construction-hour conditions written into discretionary planning permits, where the standard window is 8 a.m.–5 p.m., Monday–Friday; grading hours under § 716-8.1004; and the Noisy Animal provisions of § 416-12.202.

For everything else, the late party next door, a stereo at midnight, the governing law is California Penal Code § 415, which punishes anyone "who maliciously and willfully disturbs another person by loud and unreasonable noise" with up to 90 days in county jail, a fine of up to $400, or both. That makes it a law-enforcement matter. Call the Sheriff's Office non-emergency dispatch at (925) 646-2441, or 911 if anyone is in danger. Do not call Code Enforcement: the DCD Code Enforcement Program "enforces the building and zoning ordinances for the unincorporated areas", unpermitted construction, junk and debris, livestock on land not zoned for it, and does not take noise complaints, chronic or otherwise. Its one noise-adjacent role is written into § 82-44.418, which lets "law enforcement and code enforcement officials" monitor a permitted temporary event for compliance with its conditions and names the Director of Conservation and Development and the Sheriff as the officials who enforce that chapter.

The gap is acknowledged. On March 5, 2024 the Board of Supervisors voted 5–0 (File 24-0696) to authorize DCD to "evaluate whether additional regulation of noise is necessary and practical." The June memo followed, asking each MAC to complete a noise survey by July 31, 2024 and to nominate volunteers for a task force meeting through the fall of 2024, while noting that "many noise nuisances occur nights and weekends when limited enforcement staff are either off work or busy protecting public safety." No general noise ordinance had been adopted as of August 2026. Residents of Concord, Richmond, Walnut Creek, Antioch and the county's other incorporated cities are under their city's code, not this page.