Milpitas, CA Accessory Structures: Garage Conversions (2026)

Milpitas allows garage conversions as one path to an ADU, and Subsection C.10.030.F.5 (Design) sets the objective standards, noting they apply only to the extent state ADU law lets the city impose them. Under Subsection F.5.b (Garage conversions), once a garage is converted to an ADU, the garage door must be removed and replaced with either windows or a door; if the ADU is attached to the primary dwelling, that replacement door cannot face the street. The windows and doors installed in place of the garage door must match the size, proportion, and spacing of the primary dwelling unit's own windows and doors, so the conversion cannot leave a mismatched opening or an obviously repurposed garage bay facing the street.

The conversion sits inside the city's broader ADU size and parking rules: because livable space converted from an existing structure is exempt from the standard ADU size caps under Subsection F.1.c, a garage conversion can exceed the 1,200-square-foot detached ADU limit, and Subsection F.4.b confirms that off-street parking spaces lost when a garage, carport, or covered parking structure is converted to an ADU do not have to be replaced. A converted garage ADU still must meet the setback standards in Subsection F.2 (four feet side and rear, or the same setbacks as the structure it replaces) and the height limits in Subsection F.3, and if it houses an ADU rather than a JADU it needs only a Building Permit under Subsection D.1, moving to a Minor Site Development Permit only if it cannot meet the minimum standards in Subsection H.