Santa Clara County has updated their New Secondary Dwellings Zoning Ordinance concerning Accessory dwelling Units

If you would like to see these regulations go to

Santa Clara County provides for secondary dwellings (or Accessory Dwelling Units, or ADUs) in zoning districts that allow residential uses. There are provisions specific to rural zoning districts and urban unincorporated districts, and they vary based on lot size. ADUs may be attached or detached, newly built spaces, or converted from an existing structure. An ADU must have its own living, sleeping, eating, cooking, and sanitation facilities, including a full kitchen and bathroom. Additionally, a Junior ADU (Jr. ADU) is no more than 500 square feet and must be contained entirely within a single-family residence. It must have a separate entrance and an efficiency kitchen but may share a bathroom with primary dwelling.