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

Chapter 11.01, Development Impact Fees, requires every development project, including additions, expansions, changes of use and remodels, to pay the fees set in the City's implementing fee resolutions before a building permit issues (§ 11.01.060, § 11.01.080(A)). Section 11.01.090 lists exemptions, and subsection (A)(4) singles out accessory dwelling units: ADUs under 750 square feet owe nothing, while ADUs at or above that threshold are billed a fee scaled to 'the proportion of the square footage of the ADU to the square footage of the primary dwelling unit,' rather than the flat per-unit rate.

That formula tracks the general fee-calculation rule in § 11.01.070, which bases most fees on the unit of development actually created. Payment for a covered ADU is due in full before the building permit issues unless the applicant instead signs a recorded fee-deferral agreement with the City under § 11.01.080(B), which creates a lien against the property, specifies the amount owed, and must be released once the fee is paid; without either full payment or that recorded agreement, no city official may issue the permit or a certificate of occupancy (§ 11.01.080(D)). The current fee structure, including this ADU exemption and proration language, was last amended by Ordinance 2005 on August 12, 2025.