Tustin, CA Accessory Structures: ADU Impact Fees (2026)

Tustin City Code Section 9279(I) sets the fee rule for every accessory dwelling unit and junior accessory dwelling unit permitted in the City. An ADU that measures less than 750 square feet owes no development impact fee at all, a break the City Council adopted to track state ADU law under Ordinance No. 1517 in 2021 and amended by Ordinance No. 1535 in 2023. Once the ADU reaches 750 square feet or more, Community Development calculates the impact fee proportionally: the ADU's floor area is measured against the floor area of the primary dwelling on the same lot, and the fee scales to that ratio rather than applying the flat per-unit rate charged to a new single-family house.

Impact fees remain separately subject to any fee the City adopts under California Government Code Title 7, Division 1, Chapter 5 (commencing with Section 66000, the Mitigation Fee Act) and Chapter 7 (commencing with Section 66012), so the exact schedule tracks whatever fee resolution the City Council currently has adopted for water, sewer, park, traffic, or school facilities. The Section is explicit that "impact fee" is a narrow term here: it excludes the planning application fee charged to accept the ADU application, the plan check fee Community Development charges to review construction drawings, and the building permit fee charged before construction starts.

An applicant should expect to pay those three fees on every ADU regardless of size, with only the impact fee itself subject to the 750-square-foot threshold. A Junior ADU faces the same fee structure because Section 9279 treats ADUs and JADUs together throughout, though JADUs are capped at 500 square feet and so will typically fall under the exemption.