Before You Build in Costa Mesa, CA: Permit & Rule Checklist (2026)

Costa Mesa enforces California Building Code pool barrier requirements. All residential swimming pools and spas must be enclosed by a fence or barrier at least 5 feet tall with self-closing, self-latching gates to prevent unsupervised child access.

Costa Mesa requires building permits for retaining walls exceeding 4 feet in height measured from the bottom of the footing to the top of the wall. Walls over certain heights require engineered plans. Retaining walls near property lines must meet setback requirements.

Costa Mesa defers to California Civil Code Sections 841-841.4 for shared boundary fence responsibilities. Adjoining landowners are presumed to share equally the cost of maintaining boundary fences under the Good Neighbor Fence Act.

Costa Mesa limits front setback fences to 3 feet and side/rear fences to 6 feet maximum. Corner lots require fences over 36 inches to be set back 5 feet from the street side property line. Fences exceeding maximums require discretionary review.

Costa Mesa requires building permits for all new fences. The Planning Division reviews fence location and materials. Fences exceeding maximum heights require discretionary review. Temporary construction fencing also requires permits.

Costa Mesa applies California's Swimming Pool Safety Act (Health & Safety Code 115920-115929) and the 2022 California Residential Code through CMMC Title 5. Any above-ground pool capable of holding more than 18 inches of water requires a building permit, an isolation barrier at least 60 inches tall, and at least two of seven approved drowning-prevention features.

Costa Mesa requires plan review, permits, and inspections for swimming pool enclosures. In-ground pool permits may be issued at the counter in most cases. Building permits and electrical permits are required. Pools must meet California Building Code setback and safety standards.

Costa Mesa enforces the California Swimming Pool Safety Act requiring VGB-compliant drain covers, GFCI electrical protection, and multiple safety features. Pool owners must maintain all safety devices in working condition at all times.

Costa Mesa requires a minimum 5-foot pool barrier and at least two additional safety features under the California Swimming Pool Safety Act. Pool barriers must be maintained per California Building Code 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.

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 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 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 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 allows gas-fueled fire pits with Building Department approval. Wood-burning fire pits must maintain 25-foot clearance from combustible structures. Single-family homes (R-3) require 3-foot clearance for portable devices; other residential types require 10 feet.

Costa Mesa prohibits outdoor burning of trash and refuse. Rubbish may only be burned in approved incinerators. Gas-fueled outdoor fire devices are the primary permitted option. SCAQMD Rule 444 bans open burning in the South Coast Air Basin.

Costa Mesa maintains city-owned street trees through the Public Works Department. Private trees on residential property are the owner's responsibility. Trees must not obstruct sidewalks, streets, or create hazardous conditions for neighbors.

Costa Mesa requires approved irrigation systems for new development under its landscaping standards. Automatically time-controlled sprinklers are required for commercial, industrial, and multi-family sites. Drought restrictions from the Mesa Water District apply.