ADU short-term rental rules in San Diego and California

Airbnb ADU rules in California

State ADU law strips cities of most of their power over backyard units, but it leaves them the rental term. The statute that limits what a city can require says no extra standards may be imposed, “including an owner-occupant requirement, except that a local agency may require that the property may be used for rentals of terms 30 days or longer.” That's Government Code § 66315, as quoted in the state housing department's March 2026 ADU handbook.

There are three layers to know:

• Most ADUs: the city decides. A city or county may require rentals longer than 30 days, but it doesn't have to.
• ADUs a city must approve under § 66323: the rule is built in. These are the state-guaranteed units: a conversion inside the house or an existing accessory structure, a detached unit of up to 800 square feet with 4-foot setbacks, and ADUs on multifamily lots. For these units, the handbook says rentals “must be for terms longer than 30 days.”
• Junior ADUs: no short-term rentals at all. Since January 1, 2026, a JADU can't be used as a short-term rental and, if rented, must be rented for longer than 30 days. Our junior ADU guide covers the rest of the JADU rules.

If you're in an HOA, the association generally can't stop you from renting an ADU long term, but state law lets it prohibit “transient or short-term rental” of 30 days or less. For the wider state framework, see our guide to California ADU laws.

ADU Airbnb in San Diego: the city's rules

The City of San Diego uses the power the state gives it. Its ADU code, in the September 2026 edition, says: “An ADU shall not be used for a rental term of less than 31 consecutive days.” The city Treasurer's short-term rental FAQ is blunter: the municipal code “prohibits the use of ADUs for short term rental,” and only “permitted companion units in existence before the September 2017 prohibition” may be used. The same FAQ lists legally established ADUs among the unit types that can never get a short-term license, alongside RVs, tents and unpermitted garage rooms.

Two details in the city code are easy to miss:

• The JADU line is out of date. The city code still says JADUs “are not subject to rental term limitations,” but the 2026 state rule for JADUs controls. Treat a JADU like an ADU: more than 30 days, and 31 to satisfy both.
• Guest quarters are not an ADU. A habitable accessory building without complete living facilities is “solely for the use of the occupants of the primary dwelling unit or their guests” and “shall not be rented, leased, or sold as a separate dwelling unit” (SDMC § 141.0307). If yours was permitted that way, it can't earn rent of any length.

If you have an older unit that was never permitted, our California ADU law guide explains the state's legalization path. For long-term rent numbers, see ADU rental income in San Diego.

How San Diego's short-term rental license works

Since July 1, 2022, anyone renting a dwelling in the city for less than a month needs a short-term residential occupancy (STRO) license. It matters to ADU owners because it explains what's possible on the rest of the property. The ordinance sets four tiers:

• One license per host. A host must be a natural person, may hold only one license and may operate only one unit at a time in the city.
• Primary residence means the unit you live in at least six months a year, and you can have only one.
• Every guest gets a Good Neighbor notice covering occupancy, parking, trash and noise, and warning that the city can cite each guest and the host up to $1,000.

The ordinance doesn't make a main house ineligible just because there's an ADU behind it; the ban attaches to the ADU itself. If you want to short-term rent the main house, the tier rules above apply, and a whole-home license over 20 days a year means applying for a capped Tier 3 license, which the city issues by lottery when demand is high. Confirm your specific setup with the Treasurer before you book a guest.

Taxes on a licensed short-term rental

Any stay under a month also requires a Transient Occupancy Tax certificate. The city's TOT rate rose on May 1, 2025 from 10.5% to 11.75%, 12.75% or 13.75%, depending on the property's tax zone. Owners who rent out all or part of a property for more than six days a year also owe the Rental Unit Business Tax, which applies to long-term ADU rentals too.

Enforcement and penalties

Until recently, the city's check was thin. A September 2025 inewsource and KPBS investigation found as many as 170 properties held both a short-term rental license and an ADU, and the city's own list showed 141 ADUs, junior ADUs and guest quarters that had received licenses. The reporters also found:

• Code enforcement had issued 64 civil penalties of $1,000 per day, per violation, and the city said it had removed more than 200 listings.
• Penalties keep running until the host cancels the license and the bookings and sends proof.
• Development Services built a list of post-2017 ADUs that the Treasurer now uses to screen license applications.

A short-term rental can also complicate your coverage. Before any guest stays, read our ADU insurance guide and ask your insurer directly.

Outside the City of San Diego

Each city in the county, and the county itself for unincorporated areas, writes their own ADU rental rules, within the state limits above.

• Unincorporated San Diego County (places like Ramona, Alpine, Fallbrook and Spring Valley). The county's long-standing handout says an ADU “shall not be rented for less than 30 days.” A January 2026 draft update to the county ADU ordinance reads “shall not be rented for a term of less than 31 days.” Check which version has been adopted before you write a lease.
• Other cities. Look up the ADU section of your city's municipal code and its short-term rental ordinance. If your ADU is a JADU or was approved under § 66323, the state's longer-than-30-day rule applies wherever you are.

If you haven't built yet, factor the rental rule into the budget before you choose a design. Our guide to what an ADU costs in San Diego and the ADU cost calculator help you test whether long-term rent covers the build.

The legal alternative: 31-day ADU rentals

Furnished stays of a month or more, for traveling nurses, people between homes or visiting family, are legal in a San Diego ADU. They come with rules of their own.

• Count the days, not the months. The city's ADU rule is 31 consecutive days. The short-term rental ordinance defines a month by calendar date, so a February 1 to February 28 stay is short-term. Book at least 31 nights every time.
• Your guest is a tenant. California's landlord-tenant chapter applies to everyone who rents a dwelling, except transient occupancy subject to hotel tax. A 31-day renter isn't a hotel guest, so security deposit, habitability and eviction rules all apply.
• Short fixed terms help locally. San Diego's Tenant Protection Ordinance doesn't cover fixed-term leases of three months or less, including renewals of the same length. State law still applies.
• If a guest won't leave, you ask the court for an order to make them leave. Changing the locks or shutting off utilities to force someone out is illegal and costs up to $100 a day in penalties.

Our guide to renting out an ADU covers deposits, AB 1482, San Diego's tenant ordinance and how to end a tenancy. To build a unit for either use, compare verified ADU builders in San Diego and check a contractor's license before you sign.

Common questions