Thinking about adding an ADU (Accessory Dwelling Unit) to your property? Whether it’s for rental income, multigenerational living, or increased home value, understanding the local rules is a must. Here’s a quick breakdown of the key ADU construction rules in Orange County to help you get started.
In most Orange County cities, ADUs are allowed on single-family and multi-family lots, but always check local zoning first.
Lot Size: Some cities require a minimum of 5,000 sq ft.
Usage: ADUs are permitted for long-term rental or family use. Short-term rentals (like Airbnb) may be restricted depending on your city.
Size limits vary based on ADU type:
Detached ADUs: Up to 1,200 sq ft
Attached ADUs: Up to 50% of the main home (max 1,200 sq ft)
Junior ADUs (JADUs): Max 500 sq ft, typically carved from existing space
Your ADU must meet city development standards:
Setbacks: 4 ft from rear and side property lines for detached ADUs
Height:
One-story: Up to 16 ft
Two-story: Up to 25 ft (varies by city)
Your ADU must meet California Building Code and Title 24 energy standards, including:
Fire-rated materials (in some cases)
Up-to-code electrical, plumbing, and ventilation
Solar panels are now required on most new ADUs in California
California law makes it easier:
No parking required if the ADU is under 500 sq ft, near transit, or part of a garage conversion
When required, one off-street space is usually enough (tandem allowed)
Permits must be reviewed within 60 days of submitting a complete application.
Submit your plans and documentation to the local planning office
Expect inspections during construction
Stay in contact to avoid delays
Understanding these core rules helps you plan smarter and avoid costly mistakes. Whether you're building a rental, guest suite, or home for family, knowing the ADU construction rules in Orange County is the first step to success.