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

020(J) of Santa Clara's Title 18 Zoning Code sets out standards applicable to converted ADUs, the pathway property owners use to turn an attached garage, storage area, or a similar accessory structure such as a pool house or studio into livable accessory dwelling space. A converted ADU is defined broadly enough to include conversions from an existing primary dwelling as well as an accessory structure. The conversion may include an expansion of not more than 150 square feet beyond the existing structure's physical dimensions, but only if that expansion exists solely to provide ingress and egress to the converted space, and the converted unit must have exterior access.

The biggest practical break in the section is on setbacks: an accessory dwelling unit located within the existing space of an existing dwelling or within an existing detached accessory structure is not required to observe a setback from the rear, street side, or interior side property lines, which lets a garage sitting close to the property line convert in place. No additional off-street parking is required for the conversion; if the owner chooses to replace parking anyway, the replacement spaces can be covered, uncovered, or tandem, located anywhere on the parcel, but only on driveways leading to a required space or on a paved rear-yard surface.

Unit size caps that apply to newly built detached and attached ADUs (1,000 to 1,200 square feet depending on parcel size) do not apply to converted ADUs: the section gives the example of a 2,000-square-foot accessory structure that would not be capped when converted. Converted ADUs still fall within the ministerial approval track and are processed through a Zoning Clearance rather than discretionary review, provided the conversion meets these standards.