ADU Rules: Costa Mesa vs Midway City
How do adu rules 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 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.
View full Costa Mesa rules →Midway City, CA
Orange County
Unincorporated Orange County allows ADUs on any residentially zoned lot under OC Zoning Code (Title 7, Division 9) and California Government Code §65852.2 (ADUs) and §65852.22 (JADUs). State law preempts most local restrictions: minimum 800 sqft, 16 ft height, and 4 ft side/rear setbacks must be allowed by right.
View full Midway City rules →Key Facts Comparison
| Fact | Costa Mesa | Midway City |
|---|---|---|
| Max Size (Detached) | 1,200 sq ft | - |
| Min Size | 150 sq ft | - |
| Setback (New) | 4 ft from rear/side lines | - |
| Parking | Optional | None required if within 1/2 mi of transit or garage conversion |
| Minimum Rental | 31 days (no STR) | - |
| State Law | - | Cal. Gov. Code §65852.2 (ADU) & §65852.22 (JADU) |
| Local Code | - | OC Zoning Code Title 7, Division 9 |
| Max Detached ADU | - | 1,200 sqft |
| Max JADU | - | 500 sqft (within existing dwelling) |
| Setbacks | - | 4 ft side/rear (state minimum) |
| Height | - | 16 ft minimum allowed; up to 18-25 ft per state law |
| Owner-Occupancy | - | Required when JADU is present (§65852.22) |
Highlighted rows indicate differences between cities.
Costa Mesa FAQ
Can I build an ADU in Costa Mesa?
Yes. ADUs are permitted with a minimum size of 150 square feet and maximum of 1,200 square feet for detached units. New construction requires a 4-foot setback.
Is parking required for my ADU?
Costa Mesa makes ADU parking optional. When converting a garage, no replacement parking is required for the primary dwelling.
Can I use my ADU as a short-term rental?
No. ADUs are subject to a land use restriction prohibiting rentals under 31 days. This applies under both the ADU ordinance and the city's STR ban.
Midway City FAQ
Can I build an ADU on my unincorporated Orange County lot?
Yes — state law (Cal. Gov. Code §65852.2) requires the County to allow at least one ADU on any lot zoned for residential use, including single-family and multifamily zones. Minimum lot size requirements are preempted.
Do I need to live on the property to rent out an ADU?
No owner-occupancy is required for a standalone ADU under §65852.2. However, if you build a JADU under §65852.22, the owner must occupy either the primary dwelling or the JADU.
How tall can my detached ADU be?
State law guarantees at least 16 ft. Properties within 1/2 mile of transit or on multifamily lots can go up to 18 ft (single-story) or 25 ft (two-story) per Gov. Code §65852.2(c)(1)(D).
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