Vacaville, CA Accessory Structures: ADU Impact Fees (2026)
Key Facts
- Full exemption
- ADUs under 750 sq ft owe no impact fees
- Larger ADUs
- Fee prorated by ADU sq ft vs. primary home
- Fee due
- In full before building permit issuance
- Deferral option
- Recorded lien agreement in lieu of upfront pay
- Last amended
- Ord. 2005, August 12, 2025
Summary
Vacaville exempts accessory dwelling units under 750 square feet from all development impact fees. Larger ADUs still pay, but only a prorated share based on the ADU's square footage against the primary dwelling's square footage, not the full per-unit fee a new house would owe.
Accessory dwelling units (ADUs) of less than 750 square feet. For ADUs that are 750 square feet or larger, the fee shall be based on the proportion of the square footage of the ADU to the square footage of the primary dwelling unit.
Full Breakdown
080(A)). 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. 070, which bases most fees on the unit of development actually created. 080(D)). The current fee structure, including this ADU exemption and proration language, was last amended by Ordinance 2005 on August 12, 2025.
Violations & Fines
Chapter 11.01 is enforced at the permitting counter rather than by citation: the City cannot issue a building permit for a unit of development, including a fee-eligible ADU, unless the impact fees have been paid in full or a recorded fee agreement under § 11.01.080(B) is in place, and final inspection or a certificate of occupancy is likewise withheld until the fees are paid (§ 11.01.080(D)). Fees already paid are nonrefundable, but remain with the property as a credit toward future development if a permit is withdrawn (§ 11.01.060(C)).
Frequently Asked Questions
Do I owe development impact fees for a small backyard ADU in Vacaville?
How is the impact fee calculated for a larger ADU?
When does the ADU impact fee have to be paid?
Sources & Official References
Other rules in Vacaville
California rules heatmap·Compare Vacaville to another location·View the California accessory structures overview
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ADU Impact Fees in Nearby Cities
How other cities in Solano County handle adu impact fees.