ADU Construction in Tustin

Tustin is a centrally located Orange County city with over 115,000 residents, offering a compelling mix of older character neighborhoods and modern master-planned communities. Old Town Tustin features tree-lined streets with mid-century homes on generous lots, while the Tustin Legacy development — built on the former Marine Corps Air Station — brings newer housing, retail at The District, and open space. The city sits at the geographic heart of Orange County with direct access to the I-5 and SR-55 freeways, placing residents minutes from Irvine's massive employment base. Major employers like Blizzard Entertainment are headquartered nearby, and the diverse local economy spans tech, healthcare, and retail sectors.

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 single-story detached ADUs. Up to 25 feet for two-story ADUs per AB 1332 provisions 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

6,000–8,000 sqft typical residential lots in Tustin proper. North Tustin unincorporated areas feature significantly larger parcels, often 10,000–20,000+ sqft. 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

ADUs under 750 sqft are exempt from impact fees. North Tustin properties fall under Orange County jurisdiction, not City of Tustin — verify which entity governs your parcel before beginning the permitting process.

How to permit your ADU in Tustin

Verify zoning & jurisdiction

Confirm your property is within Tustin city limits (not unincorporated North Tustin, which falls under OC County). Check zoning on the city's GIS map and verify ADU eligibility for your parcel.

Design your ADU

Create architectural plans including site plan, floor plan, elevations, structural, mechanical, electrical, and plumbing. Consider neighborhood character — Old Town Tustin has a distinct mid-century aesthetic, while Tustin Legacy skews contemporary.

Submit plans to Community Development

Submit your complete plan set to the Community Development Department Planning Division. Include Title 24 energy compliance documentation and any required soils reports.

Plan check review (60-day)

The city reviews plans for compliance with building codes and ADU regulations. State law mandates a 60-day maximum review period for compliant ADU applications.

Build & inspect

Once permitted, begin construction with your licensed contractor. Schedule required inspections at each milestone — foundation, framing, rough mechanical/electrical/plumbing, 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 Tustin Community Development Department — Planning Division • 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.