ADU rules in San Diego

On a lot with an existing or proposed single-family home the code allows one attached or detached ADU, plus one ADU built inside the house or inside an existing accessory structure, plus one JADU. On a lot with an existing multifamily building, up to eight detached ADUs are allowed (never more than the number of existing units), plus conversions of non-livable space up to 25 percent of the unit count; a lot with a proposed multifamily building gets up to two detached ADUs. Since O-22109 (effective 7-15-2026), several detached single-family houses on one lot do not count as a multifamily building for these counts. The ADU Home Density Bonus Program can add affordable and bonus ADUs on top, capped at 4, 5 or 6 total ADUs and JADUs on single-family lots depending on lot area (Table 141-03A).

One attached or detached ADU is allowed per single-family premises, in addition to a conversion ADU and a JADU. The city's Information Bulletin 400 (January 2026) says attached ADUs are not permitted on a premises with an existing or proposed multifamily building, where the code allows conversions and detached units instead. An attached ADU is also exempt from the one parking space otherwise required in the Beach Impact Area.

ADU floor area counts toward the lot's floor area ratio, but one attached or detached ADU of 800 sq ft or less is exempt from lot coverage, floor area ratio, front setback and open space limits under Gov. Code 66321(b)(3); JADU floor area does not count toward floor area ratio. HCD's 10-6-2025 findings on O-21989 say the 1,200 sq ft cap cannot apply to detached ADUs on a lot with a multifamily building, which Gov. Code 66323(a)(4) leaves without a size limit; the city answered HCD but left the text unchanged through O-22109, so state law should control that case. The city measures size as gross floor area: a garage or carport beneath an ADU is not counted toward the 1,200 sq ft, but phantom floor area is (city ADU FAQ).

The record owner is not required to live on the same premises as an ADU. For a JADU, the codified text still requires the owner to live in the house or the JADU in every case and to sign a recorded agreement with the City, but since 1-1-2026 Gov. Code 66333(b) allows an owner-occupancy requirement only where the JADU shares sanitation facilities with the house. The city's own Information Bulletin 400 and ADU page apply that narrower rule: no owner residency when the JADU has its own bathroom, or when the owner is a government agency, land trust or qualified housing organization. Bulletin 400's paragraph on the Junior Unit Agreement still describes an owner-residence covenant, so ask the city which agreement applies to a JADU with its own bathroom.

Replacement parking is not required when a garage, carport or covered space is demolished or converted for an ADU or JADU, except for covered spaces in the Beach Impact Area outside a transit priority area; demolished or converted uncovered spaces never need replacing. Any spaces provided may sit in setbacks and may be tandem or on mechanical lifts. If an ADU leaves an existing driveway curb cut too short to meet off-street dimensions, the driveway must be closed.

ADUs and JADUs are a limited use decided by Process One (ministerial staff-level review) in base zones marked L in the Chapter 13 use tables. A building permit is required for every ADU or JADU with no exemptions, and applications using a pre-approved plan get a 30-day review (city ADU page). Coastal lots must also meet the wetland, coastal bluff, coastal beach and sea-level-rise rules listed in the section.

A STRO host may hold only one license at a time. The STRO definition of home share covers a separate dwelling unit on the host's premises, but the 31-day ADU floor in 141.0302(a)(8) controls. ADUs financed by the San Diego Housing Commission, or deed-restricted as affordable, cannot be sold separately during the restriction term; other ADUs may be converted to condominiums and sold under 141.0302(f), with a 30-day listing preference for buyers who will live in the unit.