What are ADUs?

Accessory Dwelling Units (ADUs) and Junior Accessory Dwelling Units (JADUs)

What are ADUs?

Accessory Dwelling Units (ADUs) have been known by many names: granny flats, in-law units, backyard cottages, secondary units and more. No matter what you call them, ADUs are an innovative, affordable, effective option for adding much-needed housing in California. HCD is the state’s leader on local ADU ordinances, which — while optional — have grown exponentially in number as more cities, counties, and homeowners become interested in ADUs as one solution to increasing the supply of affordable housing.

What are the benefits of ADUs?

  • ADUs are an affordable type of home to construct in California because they do not require paying for land, major new infrastructure, structured parking, or elevators.
  • ADUs can provide a source of income for homeowners.
  • ADUs are built with cost-effective wood frame construction, which is significantly less costly than homes in new multifamily infill buildings.
  • ADUs allow extended families to be near one another while maintaining privacy.
  • ADUs can provide as much living space as many newly-built apartments and condominiums, and they’re suited well for couples, small families, friends, young people, and seniors.
  • ADUs give homeowners the flexibility to share independent living areas with family members and others, allowing seniors to age in place as they require more care.

What are JADUs?

Junior Accessory Dwelling Units (JADUs) are allowed to be created within the walls of a proposed or existing single-family residence and shall contain no more than 500 square feet. JADUs offer additional housing options. They may share central systems, contain a basic kitchen utilizing small plug-in appliances, may share a bathroom with the primary dwelling, all to reduce development costs. JADUs present no additional stress on utility services or infrastructure because they simply repurpose existing space within the residence and do not expand the dwellings planned occupancy.

New! ADU Funding for Homeowners

  • New! CalHFA’s ADU Grant Program – Effective on or after September 20, 2021, the CalHFA ADU Grant Program will provide up to $25,000 in assistance to reimburse homeowners for predevelopment costs necessary to build and occupy an ADU.

New! New ADU funding laws effective January 1, 2021

  • The California Health and Safety Code (HSC), Section 65583(c)(7), requires that cities and counties develop a plan that incentivizes and promotes the creation of ADUs that can be offered at affordable rent for very-low to moderate-income households.
  • As recapped below, HCD has developed a list of existing state grants and financial incentives in connection with the expenses for the planning, construction and operation of an ADU with affordable rent for very low to moderate- income households.
    • Potential State Grants and Financial Incentives for ADUs
      • CalHome Program — State funds to local public agencies and nonprofit corporations for first-time homebuyer mortgage assistance including a home purchase with an ADU or JADU; owner-occupied rehabilitation assistance including rehabilitation of ADUs or JADUs; ADU/JADU assistance including construction, repair, and reconstruction; and homeownership development project loans including predevelopment and carrying costs during construction related to ADUs and JADUs (HCD CalHome program)
      • Local Early Action Planning (LEAP) Grants — State grants to local jurisdictions including eligible partnerships for housing planning, and developing or improving an ADU ordinance in compliance with Section 65852.2 of the Government Code (HCD LEAP program)
      • Local Housing Trust Fund (LHTF) Program — Matching funds to local and regional housing trust funds. Funds may also be used for the construction, conversion, repair, reconstruction or rehabilitation of ADUs or JADUs (HCD LHTF program)  
      • Regional Early Action Planning (REAP) Grants — Grants to council of governments (COGs) and other regional entities for activities relating to housing planning and activities including establishing Prohousing Policies such as adopting ADU ordinances or other mechanisms that reduce barriers for property owners to create ADUs (HCD REAP program)  
      • SB 2 Planning Grants — Grants to local governments including eligible partnerships for housing planning and to encourage ADUs and other innovative building types through ordinances, outreach, fee waivers, pre-approved plans, website zoning clearance assistance, and other homeowner tools or finance tools (HCD SB2 program)
      • Community Development Block Grant Program (CDBG) — Federal funds allocated to non-entitlement jurisdictions, and non-entitlement jurisdictions that partner with non-federally recognized Native American communities for community development activities including single- and multi-family rehabilitation and potential local ADU rehabilitation and planning programs. Applicants must be income qualified in low- to moderate-income households for rehabilitation and areas for planning. Contact your local jurisdictions for more information.
    • Other Potential Grants and Financial Incentives for ADUs

Accessory Dwelling Unit Handbook with updates and laws effective January 1, 2021

HCD Accessory Dwelling Unit Handbook

View Handbook

PDF download

The Legislature further updated ADU and JADU law effective January 1, 2021 to clarify and improve various provisions in order to promote the development of ADUs and junior accessory dwelling units (JADUs). These include allowing ADUs and JADUs to be built concurrently with a single-family dwelling, opening areas where ADUs can be created to include all zoning districts that allow single-family and multifamily uses, modifying fees from utilities such as special districts and water corporations, limited exemptions or reductions in impact fees, and reduced parking requirements. Please see the Accessory Dwelling Unit Handbook

PDF download

 (PDF) for more information.

Information for cities, counties, other local government bodies, utilities, other interested parties, and homeowners interested in adding an ADU or JADU to their property.

City and county HCD review letters

Although cities and counties are mandated to permit ADUs and JADUs, they are not required to adopt ADU and JADU ordinances. However, any city/county that does adopt an ADU ordinance, must submit the ordinance to HCD within 60 days.

  • Requests for adopted ADU ordinances may be emailed to: adu@hcd.ca.gov
  • HCD ADU Ordinance Review Letters and Responses from Jurisdictions
  • Excel download
    • HCD ADU Ordinance Review Letters — HCD’s review of draft ADU ordinances as well as proposals to explore and allow a variety of housing choices, including “movable” tiny homes (Placer County and the City of Los Angeles).
    • Responses from Jurisdictions — Jurisdictions are required to provide a response letter to HCD within 30 days of HCD’s ADU Ordinance Review Letter. The spreadsheet indicates whether a response letter was received.
  • ADU Technical Assistance Letters
  • Excel download
  •  (XLS) — These letters address clarification of subjects such as school fees, sewer fees and other subjects.

Sample Materials from Cities and Counties

Additional Guidance


New! Guidance from ADU Handbook contributors

You’ll find additional resources at the following websites, which are hosted by partners who contributed to HCD’s Technical Assistance Booklet.