The City Of Monte Sereno has a Guide for ADUs.


  1. An accessory dwelling unit is a separate dwelling unit that provides complete and independent living facilities for one or more people with its own kitchen (including, but not limited to stove or equivalent). The unit may be attached or detached from the primary dwelling unit.
  2. An accessory dwelling unit is permitted on any lot of at least 8,000 square feet and is limited in floor area as set out in the table provided in the Guide
  3. The floor area of an attached accessory dwelling unit shall not exceed fifty (50) percent of the existing living area of the primary dwelling or size below, whichever is less:
  4. An attached accessory dwelling unit shall comply with all the development standards of the applicable zoning district including those for the primary dwelling (See Development Standards).
  5. A detached accessory dwelling unit shall comply with the structural and impervious coverage limits of the applicable zoning district, as well as the height requirements for a primary structure. A detached accessory dwelling units shall comply with the setback requirements for an accessory structure of the applicable zoning district (See Development Standards).
  6. Accessory dwelling units must be built to meet all current building codes.
  7. Either the primary or accessory dwelling unit must be the principal residence of a legal owner of the property. The other unit may be rented.
  8. The lot or parcel must be served by the sanitary sewer system.
  9. Accessory dwelling units may be either attached or detached. If the unit is detached it must be separated from other structures by at least 6 feet. If the unit is attached to the primary dwelling the unit shall not have direct access to the primary dwelling but shall have a separate exterior entry.
  10. Accessory dwelling units may either be on the ground floor or second floor or the primary dwelling. All detached buildings are limited to one story.
  11. Accessory dwelling units shall be constructed with the materials identical in color, texture, and appearance to the primary dwelling, including but not limited to, roofing, siding, windows, and doors; and, the dwelling unit shall match the roof pitch and roof form of the primary dwelling so as to blend with the existing architecture.
  12. At least one (1) uncovered parking space shall be provided for the accessory dwelling unit in addition to the parking required for the main dwelling unit. Some exceptions apply. See Section 10.06.140 (E) for exceptions.
  13. The City provides incentives for rent restricted rental units. Please contact the City Planner for more information.

Monte Sereno Planning Department.