Vacaville, CA Accessory Structures: Garage Conversions (2026)

California Government Code 66320(a)(1) requires every California city, including Vacaville, to permit conversion of an existing garage, carport, or other accessory structure into an ADU as a ministerial action. Vacaville's VMC 14.09.122 implements this rule. The key state-law overrides applicable to garage-conversion ADUs: (1) no replacement parking required when a garage is converted (Gov. Code 66321(a)(2)) - this is one of the most homeowner-friendly aspects of the ADU statute, especially valuable in older Vacaville neighborhoods like the Downtown core, Eldridge Heights, and Markham Heights where street parking is constrained; (2) 4-foot side and rear setbacks per state default (Gov. Code 66323(g)) - existing garage walls within these setbacks may remain in place; (3) no minimum lot size override (Gov. Code 66323); (4) no architectural review beyond what is necessary to verify safety. Conversion requires a building permit through the Vacaville Building Division covering structural changes (floor leveling, insulation, drywall), electrical upgrades to residential standards (CEC), plumbing for kitchen and bath (CPC), HVAC, and Title 24 energy compliance (insulation, dual-pane windows, high-efficiency heat pump, fire-rated separation from any remaining garage space). The garage door is typically replaced with a stucco/siding wall, a residential entry door, and a window. Solano County Septic-system properties trigger Solano County Department of Resource Management review for capacity. PG&E electrical service upgrade may be required.