An accessory dwelling unit (ADU) is an accessory structure that is intended for human habitation. An ADU can be created by adding on to an existing principal dwelling or by converting existing permitted space within a principal dwelling. Additionally, a new detached ADU can be constructed or created by converting an existing detached accessory structure (garage, artist studio, pool house, etc.). Only one ADU is allowed on a legal lot.

adup examples1

ADUs are generally permitted on most lots that allow for residential development, including Open Space and Agricultural Exclusive zoned lots. Some areas of the County are within designated impact areas, where eligibility requirements for ADUs are more restrictive. Please review the Non-Coastal Zoning Ordinance Section 8107-1.7,  or the “Summary of ADU Regulations” page below, to see eligibility requirements for ADUs.

If your lot is located in the coastal area, the proposed ADU must comply with the Coastal Zoning Ordinance Section 8175-5.1.1. The ordinance is available here.

To determine the type of permit required for your ADU, see the flow chart below.

adup flowchart

Important Documents for ADU Permits:

  • Summary of ADU Development Standards: Provides a quick overview of the ADU development standards in the Non-Coastal Zoning Ordinance and Coastal Zoning Ordinance.

  • Zoning Clearance Application Form: This is the official application form to obtain a permit for an attached, detached or Interior ADU located in OS/AE zones, as shown in the flow chart above. Submittal of supplemental information will most likely be required.

  • ADU Owner-Occupant and Rental Term Affidavit: This is a required form for all ADUs that require a Zoning Clearance. It is an affidavit from the property owner agreeing that the lot in which the ADU is being proposed will be owner-occupied and that the ADU, if rented out, will be rented out for terms of no less than 30 consecutive days.

  • Parking Location Waiver Form for ADUs in Fire Hazard Severity Zones: This waiver form is for applicants whose property is located within a Fire Hazard Severity Zone. This waiver is needed if the applicant intends to utilize their driveway and setbacks to meet parking requirements. A waiver can only be granted if there are no known barriers to emergency vehicle access as determined by Fire Department staff. The County View mapping tool can assist in identifying if the property is in a Fire Hazard Severity Zone. Once you click on the County View link, input your address on the home page, then turn on the “Fire Severity Zones” layer under the “hazards” category. You should be able to determine if your house is within a Fire Hazard Severity Zone utilizing this feature.

  • Standardized Plans: The Building and Safety Division has standardized plans for ADU construction available for public use. There are three ADU sizes available: 700 sq. ft., 900 sq. ft., and 1,200 sq. ft.