Tustin Zoning and ADU Guide for Homeowners and Sellers

Last updated November 13, 2026. Reviewed by the Cash Home Buyers CA team. Information comes from the City of Tustin and the California Department of Housing and Community Development; sources are listed at the end.

Tustin allows one accessory dwelling unit and one junior ADU on a single-family lot, with attached and detached units that can reach 1,200 square feet if the home has two or more bedrooms. The standards below come from a City of Tustin council agenda report on its ADU ordinance (Ordinance No. 1535, adopted June 2023) and the city’s ADU pages.

Tustin’s Planning staff can confirm whether any later amendment changed a detail for your lot.

Tustin ADU rules at a glance

How many units Tustin allows

A single-family lot may have one ADU and one junior ADU. On multifamily lots, the city’s standards allow converting non-livable space such as storage rooms, boiler rooms, basements or garages, up to 25 percent of the existing units and at least one, and building up to two detached ADUs. Ask the Planning Division which category your property falls in.

Size limits

The ordinance sets a minimum of 150 square feet. An attached ADU may be up to 850 square feet for a studio or one-bedroom or 1,200 square feet for two or more bedrooms, and is limited to 50 percent of the existing primary dwelling. Detached ADUs follow the same 850 and 1,200 square foot caps.

A junior ADU must be between 150 and 500 square feet and sit within the existing single-family home. The city also caps an ADU plus any attached porch at 1,400 square feet combined.

Height and setbacks

Detached ADUs may be 16 feet tall, with 18 feet allowed near transit and a limited extra allowance to match the roof pitch of the main home, topping out around 20 feet. Attached ADUs may be 25 feet or the height limit of the zone, whichever is lower. Side and rear setbacks are four feet, and no setback applies when converting an existing structure or rebuilding in the same footprint.

Owner occupancy, fees and rentals

An owner does not have to live on the property when an ADU is built, but JADUs require owner occupancy. The state exempts ADUs of 750 square feet or less from impact fees, and larger units pay fees in proportion to the size of the main home.

Rentals must be longer than 30 days, and the ADU cannot be sold separately from the primary home except in the narrow cases state law allows. When you sell, the unit goes with the house.

Review time

Tustin must approve or deny a complete ADU application within 60 days under state law, and the review is ministerial, meaning no public hearing. See our Tustin building permits guide for how permit applications and inspections work.

What if my Tustin ADU or garage conversion has no permit?

Government Code section 66311.7, added by AB 2533, applies to every California city. For an ADU or JADU built before January 1, 2020, the city may not deny a permit because of building-standard violations unless correcting them is necessary for health and safety or the unit is substandard under Health and Safety Code section 17920.3.

This gives many owners of older units a realistic path to legalize. It does not make the process free: you may need drawings, corrections and inspections, and the city still decides what counts as a health and safety fix.

Call Planning at (714) 573-3140 and ask how the city handles older unpermitted units. The Tustin code enforcement guide explains what happens if the city opens a case.

How an unpermitted unit affects a sale

Sellers must disclose known unpermitted work on the Transfer Disclosure Statement. Buyers may ask you to legalize it, reduce the price, give a credit or walk away, and lenders can balk at living space that the city has no record of. Legalizing takes time and money.

A cash buyer can buy the home as it is and price the risk into the offer. See our guide to selling as-is with unpermitted work.

Common mistakes

• Advertising the unit as a legal rental when the city has no record of it.
• Assuming a garage conversion is fine because it has been there for years.
• Skipping the disclosure form to avoid scaring off buyers.
• Starting legalization work without checking whether it will actually pay for itself.

How to sell a house in Tustin with an unpermitted ADU

1. Check city records. Confirm the legal unit count and square footage.
2. Gather proof of age. Invoices, photos and utility records help show a pre-2020 build date.
3. Compare options. Legalize, sell with a credit, or sell as-is.
4. Disclose honestly. A cash offer does not change what you owe a buyer.
5. Compare net proceeds. Include repair costs, time and commissions.

See selling a house as-is in Tustin or our cash-offer process.

Questions about your unit? Call (424) 435-2326 or request a cash offer. No cost, no obligation.

Tustin zoning and ADU FAQ

How many ADUs can I build on a Tustin lot?

One ADU and one JADU on a single-family lot. Multifamily lots follow separate rules for conversions and detached units.

How big can an ADU be in Tustin?

Attached or detached ADUs up to 850 square feet for a studio or one bedroom and 1,200 square feet for two or more bedrooms; JADUs 150 to 500 square feet.

Do I have to live on the property?

Not for an ADU. A JADU requires owner occupancy.

Does Tustin charge impact fees for ADUs?

Not for ADUs of 750 square feet or less under state law; larger units pay proportionate fees.

How long does review take?

Sixty days from a complete application.

Can I legalize an older unpermitted ADU?

State law limits denial of permits for pre-2020 units over code violations unless health and safety requires correction. Ask Planning how it applies.

Can I sell a Tustin house with an unpermitted ADU?

Yes, with disclosure. A cash buyer can purchase it as-is.

Sources

• City of Tustin: Accessory Dwelling Units and City Council ADU ordinance agenda report
• California HCD: Accessory Dwelling Unit Handbook (March 2026)

This guide is general information, not legal advice. Rules change; confirm requirements with the City of Tustin.