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

California state law - now codified at Government Code 66322(a) - prohibits Vacaville from charging any impact fees on an ADU under 750 sq ft. This exempts the unit from Vacaville's Capital Facilities Fee, Park Impact Fee, Traffic Impact Fee, and Vacaville Unified School District (VUSD) and Travis Unified School District school facility fees. For ADUs 750 sq ft or larger, impact fees must be charged proportionally based on the ratio of ADU floor area to primary dwelling area, per Gov. Code 66322(a)(2). Vacaville's standard building permit and plan-check fees apply at any ADU size and are based on valuation per the Master Fee Schedule. Solano Irrigation District and the Vacaville Public Works Utilities Department (water, sewer) capacity charges may apply but are also subject to the state ADU fee exemption when the unit is under 750 sq ft. School facility fees collected by VUSD (currently around $4-5 per sq ft under Education Code 17620 and SB 50) are waived for sub-750 sq ft ADUs by state preemption. The Mitigation Fee Act (Gov. Code 66020) lets a homeowner protest impact fees within 90 days of payment if they believe a fee was charged in error.