ADU rules in Costa Mesa, CA — also called accessory dwelling unit regulations or granny flat ordinances — cover setbacks, owner-occupancy, parking, and permit requirements.
Costa Mesa permits ADUs with unique provisions including a 150 sq ft minimum size and optional parking. Detached ADUs may be up to 1,200 sq ft. Setback is 4 feet from rear and side lines for new construction. Garage conversions are exempt from setback and parking replacement requirements.
Under Costa Mesa's ADU ordinance, accessory dwelling units and junior accessory dwelling units are permitted on residential lots. Costa Mesa's unique provisions include a minimum ADU size of 150 square feet and optional parking requirements. A detached ADU on a single-family lot may not exceed 1,200 square feet. Attached ADUs are limited to the greater of 50% of the existing dwelling or 1,000 square feet. New construction ADUs require a 4-foot minimum setback from rear and interior side property lines. Conversions of legally established structures are exempt from setback requirements. When a garage is converted, no replacement parking is required. Second floor/two-story ADUs are subject to objective design standards including additional setbacks. ADUs may not be rented for less than 31 days.
ADUs built without permits are building code violations. Using an ADU as a short-term rental (under 31 days) violates both the ADU provisions and the city's STR ban.
Costa Mesa, CA
Costa Mesa Municipal Code Title 13 establishes noise standards that vary by zoning district. Industrial and commercial noise crossing into residential zones ...
Costa Mesa, CA
Outdoor music at residences, parks, and events in Costa Mesa must comply with CMMC Title 13 noise standards. Amplified outdoor music requires compliance with...
Costa Mesa, CA
Costa Mesa regulates amplified music under CMMC Chapter XIII noise control. Music and sound-producing devices must comply with exterior noise standards at th...
Costa Mesa, CA
Costa Mesa defines abandoned vehicles as those left on public streets for more than 72 hours without being moved or those that are inoperable. The city proac...
Costa Mesa, CA
Costa Mesa prohibits commercial vehicles over 10,000 pounds GVW from parking on restricted streets between 2 AM and 6 AM, or for more than 3 hours on any pub...
Costa Mesa, CA
Costa Mesa requires vehicles to park on improved surfaces under its development and property maintenance standards. Driveway design must meet zoning requirem...
Side-by-side rule comparisons with other cities in Orange County.
See how other cities in Orange County handle adu rules.
See how Costa Mesa's adu rules rules stack up against other locations.
Help us keep this page accurate. If you notice an error or outdated information, let us know.