Garage Conversions: Costa Mesa vs Midway City
How do garage conversions rules compare between Costa Mesa, CA and Midway City, CA?
Midway City has fewer restrictions than Costa Mesa.
Costa Mesa, CA
Orange County
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.
View full Costa Mesa rules →Midway City, CA
Orange County
Unincorporated Orange County allows the conversion of an existing garage, carport, or accessory structure into an accessory dwelling unit (ADU) under Section 7-9-90 of the Codified Ordinances and California Government Code Section 65852.2. A garage-conversion ADU may be the size of the converted structure plus up to 150 square feet for ingress/egress, processed ministerially, and the parking space lost in the conversion does not need to be replaced.
View full Midway City rules →Key Facts Comparison
| Fact | Costa Mesa | Midway City |
|---|---|---|
| Parking Replacement | Not required under CA ADU law | Not required (Sec. 7-9-90(d)(3)) |
| Building Permit | Required for all conversions | - |
| Ceiling Height | Minimum 7 feet for habitable space | - |
| Impact Fees | Waived for ADUs under 750 sq ft | - |
| Authority | - | OC Codified Ord. Sec. 7-9-90 |
| State Law | - | Cal. Gov't Code 65852.2 / 65852.22 |
| Conversion Size | - | Existing footprint + up to 150 sq ft ingress/egress |
| Max Size | - | 1,200 sq ft (ADU); 500 sq ft (JADU) |
| Permit Process | - | Ministerial (60-day review) |
| Short-Term Rental | - | Prohibited (Sec. 7-9-90(c)(5)) |
| Permit Authority | - | OC Public Works Development Services |
Highlighted rows indicate differences between cities.
Costa Mesa FAQ
Can I convert my garage to an apartment in Costa Mesa?
Yes. California ADU law allows garage-to-ADU conversions without requiring replacement parking spaces. You need a building permit, and the conversion must meet Building Code standards for habitable space including egress, ventilation, and minimum ceiling height.
Do I need to add parking if I convert my garage to an ADU?
No. California Government Code Section 65852.2 specifically prohibits cities from requiring replacement parking when an existing garage is converted to an ADU. This applies regardless of your zone or neighborhood.
How much does it cost to get a garage conversion permit in Costa Mesa?
Permit fees vary based on the scope of work. Impact fees are waived for ADUs under 750 square feet under state law. Contact the Building Division at (714) 754-5245 for a fee estimate based on your specific project plans.
Midway City FAQ
Do I have to replace the parking space if I convert my garage to an ADU in unincorporated Orange County?
No. Section 7-9-90(d)(3) of the Orange County Codified Ordinances expressly states that no replacement of removed parking spaces is required when an existing garage, carport, or covered parking garage is converted to an ADU or removed to accommodate ADU construction. This mirrors California Government Code 65852.2 and is one of the strongest permissive ADU rules in the state.
How big can my garage-conversion ADU be?
Section 7-9-90(a)(2) caps a conversion ADU at the square footage of the converted structure, up to 1,200 square feet. Section 7-9-90(c)(1) separately allows an expansion of up to 150 square feet beyond the existing dimensions for ingress/egress (which counts toward the maximum). A junior ADU is capped at 500 square feet under Section 7-9-90(a)(3) and Government Code 65852.22.
Can I rent out my converted garage on Airbnb?
No. Section 7-9-90(c)(5) prohibits any ADU or JADU from being used as a short-term rental of less than 30 days. The unit may be used as a long-term rental of more than 30 days. Short-term-rental use can support administrative action against the ADU and code-enforcement penalties.
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