Tustin, CA Accessory Structures: ADU Rules (2026)

Section 9279 governs both ADUs and Junior ADUs on any lot zoned for single-family or multi-family residential use, adopted to track State ADU law under Ordinance No. 1517 (Section XIII, December 7, 2021) and later amended by Ordinance No. 1535 (Section 4, June 20, 2023). A single-family lot gets no more than one attached, converted or detached ADU; a multi-family lot can add up to two detached ADUs, plus converted ADUs inside non-livable space such as storage rooms, boiler rooms or garages, capped at twenty-five percent of the existing unit count.

Size limits track bedroom count: an attached studio or one-bedroom ADU maxes out at 850 square feet, and a two-or-more-bedroom attached unit at 1,200 square feet, each also capped at fifty percent of the primary dwelling's floor area; detached units follow the same 850- and 1,200-square-foot ceilings without the percentage cap. Height is capped at sixteen feet for a detached ADU on a lot with a single-family or single-story multi-family home, rising to eighteen feet (twenty feet to match a primary roof pitch) within a half mile of a major transit stop, and to twenty-five feet or the district limit, whichever is lower, for an attached unit.

Side and rear setbacks are a minimum of four feet; front setbacks match whatever applies to other structures on the lot, and converted ADUs need no new setback if the existing structure already meets fire and safety requirements. The Community Development Director reviews a complete ADU application ministerially, without a hearing, within sixty days, and no impact fee applies to any ADU under 750 square feet.