ADU Construction in Orange

The City of Orange is one of the most architecturally distinctive communities in Orange County, anchored by the Old Towne Historic District — one of the largest National Register-listed historic districts in California. Home to Chapman University and its 10,000+ students, Orange features established neighborhoods with mature landscaping and generous lot sizes. Orange Park Acres, a unique semi-rural enclave within the city, offers half-acre to multi-acre equestrian properties ideal for large detached ADUs. The city's central OC location provides easy access to the 55, 57, and 22 freeways, connecting residents to employment centers in Irvine, Anaheim, and Santa Ana.

Zoning & requirements

Setbacks

4-foot minimum from rear and side property lines for new detached ADUs. Conversions of existing structures are exempt from setback requirements.

Height

Up to 16 feet for detached ADUs. Up to 25 feet for attached ADUs in qualifying residential zones.

Parking

One parking space per ADU may be required. Exempt if within 0.5 miles of public transit, within one block of a car-share vehicle, or if the ADU is a conversion of existing space.

Lot Size

6,000–10,000+ sqft for standard residential neighborhoods. Orange Park Acres lots range from 0.5 to 5+ acres. No minimum lot size required by state law to build an ADU.

Owner Occupancy

No owner-occupancy requirement for ADUs (made permanent by AB 976 in 2025).

Additional Notes

Properties within the Old Towne Historic District require design review conforming to the Secretary of the Interior's Standards for the Treatment of Historic Properties. The city requires a minimum of 2 exterior colors and at least 3 distinct architectural elements (e.g., varied roofline, window trim, wainscoting, decorative vents) on ADU facades. Orange Park Acres properties may have additional equestrian overlay zoning considerations.

How to permit your ADU in Orange

Verify zoning & historic status

Check your property on the City of Orange zoning map. Critically, determine whether your parcel falls within the Old Towne Historic District — if so, your ADU design must conform to the Secretary of the Interior's Standards and undergo additional design review.

Design your ADU

Create architectural plans that include 2 exterior colors and at least 3 architectural elements as required by the city. For Old Towne properties, ensure the design is compatible with the historic character of the neighborhood.

Submit plans to Planning Division

Submit your complete plan set to the Planning Division at 300 E. Chapman Avenue. Include structural engineering, Title 24 energy compliance, and a soils report if required. Old Towne properties will be routed for historic review.

Plan check review

The city reviews plans for compliance with building codes and ADU regulations. State law mandates a 60-day maximum review period. Old Towne historic review may run concurrently but can add processing time.

Build & inspect

Once permitted, begin construction with your licensed contractor. Schedule required inspections at each milestone — foundation, framing, rough MEP, insulation, and final.

Final inspection & occupancy

Request final inspection from the Building Division. Once passed, receive your Certificate of Occupancy. Your ADU is now legal to rent or occupy.

City of Orange Planning Division — 300 E. Chapman Avenue • Fees: $5,000–$12,000 total (plan check, building permit, school fees). Impact fees waived for ADUs under 750 sqft. • Timeline: 4–8 weeks for plan check. 60-day maximum review required by state law. Old Towne historic review may add additional time.