Accessory Structures in Costa Mesa, CA (2026)
5 verified accessory structures rules for Costa Mesa, California, sourced directly from the municipal code and official government pages.
Verified from official government sources
ADU Rules
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.
Costa Mesa ADU Regulations
Some RestrictionsShed Rules
Costa Mesa requires building permits for storage sheds exceeding 120 square feet in floor area. Sheds 120 square feet or smaller and not exceeding 6.5 feet in height may have a zero rear yard setback in the R1 zone and generally do not require a permit. All sheds must comply with lot coverage limits and may not be used for habitation. Sheds in required side yards must meet minimum setback requirements.
Costa Mesa Shed Rules and Permit Requirements
Some RestrictionsGarage Conversions
Costa Mesa allows garage conversions to accessory dwelling units (ADUs) under California ADU law (Government Code Sections 65852.2 and 65852.22). Converting a garage to an ADU does not require replacement parking spaces. The conversion must meet Building Code requirements for habitable space including proper egress windows, insulation, ventilation, and plumbing. A building permit is required for all garage conversions.
Costa Mesa Garage Conversion Rules
Some RestrictionsCarport Rules
Costa Mesa regulates carports through Title 13 (Zoning) of the Costa Mesa Municipal Code and Title 5, which adopts the 2022 California Building and Residential Codes. A carport is a structure that requires a building permit, must meet the setbacks of the underlying zone, and counts toward required covered parking for single-family homes.
Costa Mesa Carport Rules
Some RestrictionsTiny Homes
Costa Mesa permits foundation tiny homes as Accessory Dwelling Units under CMMC Title 13 and California Government Code Section 65852.2, which preempts most local restrictions for ADUs up to 1,200 sq ft. California Residential Code Appendix AX (effective 2023) sets construction standards for tiny houses on permanent foundations 400 sq ft or less. Tiny houses on wheels are classified by HCD as recreational vehicles.
Costa Mesa Tiny Home Rules
Some RestrictionsLooking for Orange County county-wide rules?
County ordinances apply to unincorporated areas and may supplement Costa Mesa city rules.
Accessory Structures in Orange County →