What are the ADU rules in San Diego in 2026?

As of October 2026, state law sets San Diego's floor: ADUs of at least 850 sq ft (1,000 sq ft with two or more bedrooms), 4-foot side and rear setbacks, no owner-occupancy rule and no impact fees at 750 sq ft or less. The city adds its Bonus ADU program, which the City Council narrowed in 2025.

Every rule on this page is stated as of October 2026. State rules come from the HCD ADU Handbook (updated March 2026). City rules come from City of San Diego publications and news coverage cited below. Rules change, so treat this as the starting point for your lot, not the final word.

What does state law guarantee a San Diego lot?

• Size. A city's maximum must allow at least 850 sq ft, or 1,000 sq ft for more than one bedroom, measured as interior livable space. Local lot coverage, floor area and open space rules cannot block an 800 sq ft ADU with 4-foot side and rear setbacks.
• Setbacks. No more than 4 feet at the sides and rear. None for a unit built inside an existing structure or rebuilt in the same footprint.
• Height. 16 feet for a detached ADU, 18 feet within half a mile of a major transit stop or high-quality transit corridor (plus up to 2 feet to match the main roof pitch), and 25 feet or the zone limit, whichever is lower, for an attached ADU.
• Parking. None may be required within half a mile walking distance of public transit, in an architecturally and historically significant historic district, for a unit inside the home or an existing accessory structure, where on-street permits are not offered to the occupant, or within one block of a car share vehicle. Converting or demolishing a garage for an ADU does not trigger replacement parking.
• Fire sprinklers. Only required in the ADU if the main home is required to have them.

How many units can go on a single-family lot?

The HCD Handbook describes a combination cities must allow on a single-family lot: one ADU converted from existing space, one junior ADU, and one new detached ADU, subject to conditions in the law. The City of San Diego's planning page describes one ADU plus one junior ADU on a single-family lot before any Bonus ADU units. Which combination fits depends on how your lot and existing buildings are laid out, so we confirm it address by address.

What is San Diego's Bonus ADU program?

As of October 2026, the city's planning page describes the program this way: for each ADU deed-restricted as affordable to very low, low or moderate income households for 15 years, the owner can add one bonus ADU. Inside Transit Priority Areas the program has historically had no cap on the total number of ADUs; outside them, one bonus unit is allowed with no additional bonus.

What changed in the 2025 Bonus ADU reforms?

The City Council approved a package of reforms in mid-2025. As reported by the city and by KPBS, the changes include:

• a maximum total unit count tied to lot size (KPBS reported caps of four ADUs on lots of 8,000 sq ft or less, five on 8,001 to 10,000 sq ft, and six above that)
• one off-street parking space for each affordable and bonus ADU outside a Transit Priority Area
• on lots in High or Very High Fire Hazard Severity Zones, a requirement to front an improved public street with at least two evacuation routes
• a Community Enhancement Fee on bonus and affordable ADUs under 750 sq ft
• removal of the program from several RS-1 single-family zones, except in high- and highest-resource areas

As last reported (December 2025), most changes took effect August 22, 2025 outside the coastal zone, while coastal zone implementation still needed California Coastal Commission certification. Check the current status before planning a multi-unit Bonus ADU project.

Can I sell an ADU separately in San Diego?

In many cases, yes. State law lets each city decide whether to allow ADUs to be sold separately as condominiums, and the City of San Diego's August 2025 update to Information Bulletin 400 says most new or existing ADUs may now be sold separately from the main home. A condominium map and other requirements still apply.

Can I rent an ADU on Airbnb in San Diego?

Generally not. As reported by KPBS in September 2025, the city bars short-term rentals in any ADU permitted after September 2017. State law separately requires junior ADU rentals to be longer than 30 days.

Does the owner have to live on site?

Not for an ADU. As of October 2026, state law (AB 976) prohibits owner-occupancy requirements on ADUs, apart from a narrow nonprofit sale exception. For a junior ADU, an owner-occupancy rule is allowed only when the JADU shares a bathroom with the main home.

What changed statewide for 2026?

Bills passed in 2025 took effect for 2026. HCD's summary includes measuring ADU size by interior livable space, a 15-business-day completeness check, impact fee thresholds of 750 sq ft for ADUs and 500 sq ft for JADUs, tying JADU owner occupancy to a shared bathroom, rentals longer than 30 days for JADUs, and a 60-day review period inside the coastal zone.