Santa Clara County, CA Accessory Structures: Garage Conversions (2026)

Garage conversions in unincorporated Santa Clara County are primarily handled as accessory dwelling unit conversions under Zoning Ordinance Section 4.10.015(H). That subsection applies to ADUs created by converting an existing, legal detached accessory building that received a final inspection prior to January 1, 2017, or from existing floor area within a primary residence. A setback-nonconforming detached garage or other accessory building may be converted, preserving the existing footprint, in line with California ADU law (formerly Government Code Section 65852.2, recodified at Government Code Sections 66310-66342), which limits a county's ability to require correction of nonconforming setbacks for conversion ADUs. Standard detached-ADU rules otherwise apply: the dwelling portion may not exceed 1,200 square feet, side and rear setbacks of at least four feet, and a 16-foot height limit where single-family setbacks are not met. A detached ADU design may also incorporate an attached garage or carport of up to 400 square feet without counting toward the 1,200-square-foot living-area cap. Building permits are reviewed ministerially within 60 days. Because the conversion creates a dwelling unit, it must meet state building standards for habitability, water and wastewater service, and fire-life-safety requirements. If a garage is converted and replacement parking is at issue, state ADU law restricts when a county may require it.