The City of Santa Clara defines an accessory unit as one additional dwelling unit that includes a single kitchen, sleeping quarters, not more than one bathroom, and not more than two bedrooms on a lot 6,000 square feet or greater or one bedroom on a lot less than 6,000 square feet, on a lot with an existing single-family dwelling. The accessory unit may be attached to or part of the existing single-family unit or may be a detached structure and shall meet all other requirements of the Zoning Ordinance, including design compatibility with the main residence in accordance with the City’s design guidelines.

Accessory units are permitted by right in the R1-6L – Single-Family Zoning District and R1-8L – Single-Family, Larger Lot Area Zoning District on lots that have an existing single-family dwelling.

Roof, siding and windows must be consistent with the roof slope, materials and design of the main dwelling unit.

The City has published a handout with guidelines:  “Accessory Unit Administrative Review”