California ADU rules · Orange County
Can I Build an ADU in Tustin?
Yes — you can build an ADU in Tustin. California's statewide ADU law requires every city, including Tustin, to approve a qualifying accessory dwelling unit by right, plus a junior ADU (JADU) on a single-family lot. What varies city to city are the local specifics below.
Can you build one?
ADUs allowed
CA state lawYes — by right
ADUs and JADUs are allowed by right in all residential and mixed-use zones; ministerial approval, no hearing.
Units on a single-family lot
Local rule1 ADU (attached, detached, or converted) + 1 JADU; if both detached ADU and JADU, detached ADU max 850 sq ft
Detached ADU is limited to 850 sq ft if both a detached ADU and JADU are built on the same lot.
Units on a multifamily lot
Local ruleConverted ADUs: up to 25% of existing units (rounded down, min 1); Detached ADUs: up to 2 per lot
Detached ADUs on multifamily lots are capped at 2 per lot, not 8 as in state baseline.
Junior ADU (JADU)
CA state lawAllowed
Up to 500 sq ft, within the walls of an existing single-family home (single-family lots only).
Size & height
Max detached ADU size
Local rule850 sq ft
Detached ADU max is 850 sq ft for studio/1-bedroom, 1,200 sq ft for 2+ bedrooms; but if both detached ADU and JADU, detached ADU is capped at 850 sq ft.
Max attached ADU size
Local ruleStudio/1-bedroom: lesser of 850 sq ft or 50% of primary (but at least 850 sq ft if primary <1,700 sq ft); 2+ bedrooms: lesser of 1,200 sq ft or 50% of primary (but at least 1,200 sq ft if primary <2,400 sq ft)
Local rule sets both a percentage and a minimum/maximum for attached ADUs.
Guaranteed minimum size
CA state law800 sq ft
An 800 sq ft ADU must be allowed regardless of FAR/lot-coverage caps; a city also cannot cap an attached ADU below 850 sq ft (1,000 for 2+ bedrooms).
Max JADU size
CA state law500 sq ft
Max height
CA state law16 ft
16 ft baseline; cities must allow 18 ft within ½ mi of a major transit stop or where the primary dwelling is two-story, and 20 ft on a lot with a multistory multifamily building.
Setbacks
Side setback
CA state law4 ft
A city cannot require more than 4 ft side or rear setback; conversions of existing structures are exempt.
Rear setback
CA state law4 ft
Front setback
CA state lawNo front setback may block the mandatory 800 sq ft / 16-ft / 4-ft-setback ADU; otherwise per base zone
Separation from main house
CA state lawNone required
No statewide separation requirement between the ADU and the primary dwelling.
Parking
Parking required
CA state lawUp to 1 space
At most 1 space per ADU (or per bedroom, whichever is less) — and waived in the common cases below.
Transit parking exemption
CA state lawYes — no parking required near transit & for conversions
No parking may be required within ½ mi walking distance of transit, in a historic district, for an ADU within an existing structure, within one block of car-share, or in certain permit-parking areas.
Garage-conversion replacement parking
CA state lawNot required
When a garage/carport is demolished or converted to build an ADU, replacement parking cannot be required.
Approval, timeline & cost
Approval path
CA state lawMinisterial (by right)
No public hearing or discretionary design review for a qualifying ADU.
Approval timeline
CA state law60 days
The agency must act within 60 days of a complete application — and the ADU is deemed approved if it does not.
Owner-occupancy
Local ruleOnly for a JADU
Owner occupancy required only for JADUs, not for ADUs.
Impact-fee waiver
CA state lawWaived under 750 sq ft
An ADU of 750 sq ft or less pays no impact fees (the 750 sq ft threshold itself is exempt under § 66311.5); larger ADUs pay fees proportional to the primary dwelling. JADUs (≤ 500 sq ft) are exempt.
Permits required
CA state lawBuilding permit
Only a ministerial building permit — no conditional use permit or discretionary design review for a qualifying ADU.
Tustin-specific factors that can change the answer
State law sets the floor, but these local conditions often decide whether a specific parcel works.
Historic Preservation Overlay Zone (HPOZ)
ADU/JADU must not cause substantial adverse change to historic properties
Tustin limits detached ADUs to 2 per multifamily lot (not 8), and if both a detached ADU and JADU are built on a single-family lot, the detached ADU is capped at 850 sq ft. Height and attached ADU size rules are more detailed than state minimums.
Frequently asked questions
Can I build an ADU in Tustin?
Yes. California's statewide ADU law requires Tustin to approve a qualifying accessory dwelling unit ministerial (by right), plus a junior ADU (JADU) on a single-family lot.
How big can an ADU be in Tustin?
A detached ADU of at least 850 sq ft must be allowed, and an ADU of 800 sq ft can never be zoned out by floor-area or lot-coverage limits. A JADU can be up to 500 sq ft.
What are the setback requirements for an ADU in Tustin?
Side and rear setbacks are limited to 4 ft. No front setback may block the mandatory 800 sq ft / 16-ft / 4-ft-setback ADU; otherwise per base zone.
Is parking required for an ADU in Tustin?
Up to 1 space. No parking can be required within ½ mile of transit, for conversions, or for units inside the primary home. When a garage is converted, replacement parking is not required.
How long does ADU approval take in Tustin?
A complete application must be acted on within 60 days, with ministerial (by right) — no public hearing or discretionary design review for a qualifying ADU.
Do I have to live on the property to build an ADU in Tustin?
Owner-occupancy: only for a jadu. ADUs under 750 sq ft are also exempt from impact fees.
Sources
- Tustin Zoning Code § 9279 (Ord. No. 1536, Sec. 17, amended April 16, 2024)
- Tustin Zoning Code § 9279.D.3(a)
- Tustin Zoning Code § 9279.D.3(b)
- Tustin Zoning Code § 9279.D.4(a)ii, § 9279.D.3(a)
- Tustin Zoning Code § 9279.D.4(a)i
- Tustin Zoning Code § 9279.F.3
- Tustin Zoning Code § 9279.F.4
- Cal. Gov. Code §§ 66310–66342 (ADU Law)
- HCD 2025 Accessory Dwelling Unit Handbook
- Cal. Gov. Code § 66317 (ministerial approval, 60-day deadline)
- Cal. Gov. Code § 66333 (junior ADUs)
- Cal. Gov. Code § 66321 (size minimums & height)
- Cal. Gov. Code § 66323 (by-right ADU/JADU, 800 sq ft, 4-ft setbacks)
- Cal. Gov. Code § 66322 (ADU parking; § 66334 covers JADU parking)
- Cal. Gov. Code § 66314 (local ordinance standards)
- Cal. Gov. Code § 66311.5 (impact fees: none for an ADU ≤ 750 sq ft or JADU ≤ 500 sq ft)
Last updated 2026-06-25. This is an AI-assisted summary of Tustin's ADU rules, drawn from its published ordinance and California ADU law — general information, not legal advice, and it may be incomplete or out of date. Verify the controlling rule for your specific parcel with Tustin Planning before relying on it.
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