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ADUs In Orange County

Last updated November 3, 2026

Orange County Development Services lists six pre-approved floor plans for new detached ADUs, from a 393 square foot studio to a 1,200 square foot three-bedroom, and an AB 2533 Safe ADU/JADU Legalization Program for units built without permits. Many addresses sit inside cities with their own ADU rules, so confirm which agency governs yours.

The Local Program

Orange County Development Services lists pre-approved ADU plans and an AB 2533 Safe ADU/JADU Legalization Program. Its pre-approved plans page offers six floor plans for new detached ADUs, from a 393 square foot studio to a 1,200 square foot three-bedroom, applied for through the county's online portal. The county says the plans currently reflect the 2022 California Building Code and are being updated for the 2025 code. Many Orange County addresses sit inside cities that have their own ADU rules, so confirm which agency governs yours.

What Costs Look Like In The Region

The Terner Center's Terner Center statewide ADU owner survey reports a median of $130,000, or $200 per square foot, for Orange and San Diego Counties together. That survey was published in 2021, so current prices may be higher. See ADU Cost In California for the full table and the caveats.

What To Check At Your Address

• Confirm whether your address is in a city or in unincorporated county land before reading any program page.
• The legalization program matters if an older garage or backyard unit was built without permits.
• Ask the county whether site work such as grading or a septic system adds review.

State Rules That Apply Here

• The review deadlines in Permits And Timeline: 15 business days for a completeness notice and 60 days to approve or deny a complete application.
• No impact fees for an ADU of 750 square feet or less (Government Code section 66311.5).
• No owner occupancy requirement for an ADU (Government Code section 66315).

Before You Hire Anyone

Call or visit the planning counter, and bring your address and a sketch of what you have in mind. Then read Questions To Ask An ADU Builder.