Accessory Dwelling Ordinance

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What is an ADU? | Benefits of an ADUContact

2020 Amendments

New State housing laws that went into effect on January 1, 2020, grant more flexibility to construct Accessory Dwelling Units (ADU) across California. Redwood City is in the process of updating its local ADU ordinance to be compliant with State regulations. The Planning Commission and City Council are tentatively scheduled to hold a Joint Study Session on February 10, 2020 to discuss the new State ADU regulations and the required considerations for adopting a local ordinance. No formal action will take place at the meeting.  In the interim, the City will review ADU projects under the State ADU regulations. Below is a summary of new changes to the State ADU law:

Development Standards

  • Cities are required to allow junior accessory dwelling units (JADUs). These are units of up to 500 square feet of converted space contained entirely within a single-family home. A JADU may share a bathroom with the existing home.
  • ADUs will be allowed in multi-family units. Conversion of uninhabited spaces, including garages, will be allowed for at least one ADU or up to 25% of units in multi-family buildings. Plus, up to two detached ADUs with 4-foot setbacks will also be allowed.
  • Cities must allow a minimum of 850 square feet for a one-bedroom ADU, or 1,000 square feet for an ADU with more than one bedroom.
  • Cities are prohibited from implementing any lot coverage, floor area ratio, and/or open space requirements for detached ADUs.

 Process Updates

  • Cities may not impose impact fees on ADUs less than 750 square feet. 
  • There is a 5-year moratorium on local owner-occupancy restrictions.
  • Mandatory 5-year stay of enforcement on unpermitted ADUs, if they meet health and safety standards.
  • Short-term rentals of ADUs or JADUs are not permitted.
  • California Department of Housing and Community Development (HCD) & the Attorney General can enforce compliance if a new local ordinance is out of compliance, but it provides a 30-day right to sure or state findings to support the local ordinance.

For more information and a full list of new State ADU laws, go here. (Provided by the San Mateo County Department of Housing)

2019 Amendments

The City has prepared a series of proposed zoning amendments to address concerns around height and privacy of second-story accessory dwelling units (ADU) above detached garages in rear yard, and to explore ways to incentivize one-story ADUs. These concerns stemmed from recent changes in the ADU regulations due to state law requirements. These draft amendments were reviewed by the Planning Commission on  May 21, 2019 and June 18, 2019 and the City Council on July 22, 2019 and adopted on August 26, 2019. The regulations went into effect September 25, 2019. The City Council adopted the following amendments:

Second Story ADUs and Privacy:

  • Reduce maximum heights for second-story ADUs above garages from 28 ft. to 20 ft. with additional roof height that complements the roof pitch of the main single-family dwelling, as determined by the Zoning Administrator.
  • Limit portions of the ADU above garages to 576 square feet.
  • Prohibit all balconies and second-story decks on detached ADUs.
  • Prohibit roof decks above accessory structures to reduce privacy impacts.
  • Restrict exterior stairs facing immediately adjacent neighbors to reduce privacy impacts.
  • Require opaque or clerestory windows when facing immediately adjacent side and rear neighbors to reduce privacy impacts.

One-Story ADU Incentives:

  • Reduce single-story rear setbacks from 10 ft. to 6 ft.
  • Exempt ADUs from a 50% rear lot coverage requirement to increase buildable footprint in the rear yard.
  • Allow replacement of detached garages into ADUs to ensure new structures comply with setbacks and to prevent two-story structures in the rear yard.
  • Increase ADA compliant ADU maximum size from 800 sq. ft. to 1,000 sq. ft. in order to incentivize construction.
  • Exempt one-story ADUs from the Hillside Ordinance to reduce further barriers to ADU construction.

2017 Amendments

In response to a new State Law, the City Council amended the Accessory Dwelling Unit ordinance and made consistency changes to other sections of the code (Public Hearing of March 27, 2017). The new state law restricts what cities may require of new ADUs with the intent of further reducing barriers, streamlining approval, and expanding capacity to accommodate the development of ADUs.

The Cities ordinance:

  • Removes requirement for one additional parking space with ADUs
  • Allows conversion of the garage into an ADU with replacement parking spaces on the driveway
  • Increases base maximum size from 640 sq. ft. to 700 sq. ft. and eliminates the limitation on number of bedrooms
  • Permits conversion of accessory structures into an ADU with setbacks required for fire safety
  • Allows one of the two required parking spaces for a single-family home to be uncovered and on the driveway
  • Eliminates the two-water fixture limitation for accessory buildings.


  • To apply for a permit to construct an ADU, fill out the ADU Completeness Checklist and a Building Permit application. 
  • Planning Commission Recommendations to ADU Changes, Home Size Limits and Residential Design Guidelines Next Steps blog, go here.

What is an Accessory Dwelling Unit?

An Accessory Dwelling Unit (ADU) is a smaller living unit on a property that has a single-family residence. It is complete with its own kitchen and bathroom facilities.  Common names for an ADU include in-law unit, secondary unit, and backyard cottage. ADUs are not allowed to be used exclusively as a short-term rental unit.

Benefits of an ADU

  • Extra living space for family or guests
  • Housing for aging parents, caregivers or adult children
  • Efficient use of existing infrastructure
  • Rental income

City Council Phased Approach to Preserve Affordability and Architecture Character of Redwood City Neighborhoods


Apollo Rojas
Associate Planner
(650) 780-7365

PC Notice 10.06.15