Accessory Dwelling Units (ADUs)
- What are ADUs?
- New law effective January 1, 2019
- Other recent updates to state laws for ADUs - Includes webinar
- Technical Assistance Booklet - Includes FAQs and sample ordinances
- City and county ADU ordinances and HCD review letters
- Sample materials from cities and counties
- Additional guidance
- External websites (contributors to Technical Assistance Booklet)
What are ADUs?
Accessory Dwelling Units (ADUs) are 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.
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.
New law effective January 1, 2019
As of January 1, 2019, homeowners who created accessory dwelling units (ADUs) without the required building permits may have the opportunity to bring their ADUs into compliance. For ADUs that were constructed without building permits, local building officials now have the option to inspect an ADU and apply the building standards that were in effect at the time the unit was constructed. This bill: SB 1226 (Bates), adds Section 17958.12 to the California Health and Safety Code , and with application of appropriate building codes, may allow issuance of a building permit for the residential unit.
Other recent updates to state laws for ADUs
Effective January 1, 2018
The Legislature further updated ADU law effective January 1, 2018, to clarify and improve various provisions in order to promote the development of ADUs. These include allowing ADUs to be built concurrently with a single-family home, opening areas where ADUs can be built to include all zoning districts that allow single-family uses, modifying fees from utilities, such as special districts and water corporations, and reducing parking requirements. Please see the HCD Technical Assistance Memorandum: Accessory Dwelling Unit Legislation (PDF), for more information.
State legislation that took effect January 1, 2017 gave California cities more flexibility and latitude for allowing homeowners to build ADUs. Three separate bills were introduced and signed by Governor Brown; SB 1069 (Wieckowski), AB 2299 (Bloom), and AB 2406 (Thurmond). Each of these land use bills make it easier than ever for homeowners to take advantage of this attractive opportunity.
Webinar : Recent Legislation "Nuts and Bolts"
Technical Assistance Booklet
Download entire booklet (PDF)
Information for cities, counties, other local government bodies, and homeowners interested in adding an accessory dwelling unit to their property.
Download the entire booklet (PDF) or select one of the following excerpts:
City and county ADU ordinances and HCD review letters
Cities and counties are not required to create ordinances for ADUs; however, any city/county that does adopt an ADU ordinance, must submit the ordinance to HCD within 60 days.
Sample materials from cities and counties
- ADU flyer (PDF) - Sonoma County
- Junior ADU flyer (PDF) - Sonoma County
- ADU guidebook - City of Los Angeles
- ADU General Info Trifold (PDF) - Healdsburg
- ADU General Info Trifold (PDF) - City of Dublin
- ADU General Info Trifold (PDF) - City of Fremont
- ADU guidelines (PDF) - City of San Luis Obispo
- ADU Impact Fee Schedule (PDF) - City of Reedley
- California State Fire Marshal (PDF) - Information bulletin regarding sprinkler system requirements.
- CalHFA (PDF) - Bulletin for ADU income which includes anticipated income from planned ADU to qualify for loan to create the ADU.
- California Energy Commission updates for ADU:
- Blueprint Newsletter Issue 122 (PDF) — ADU FAQs for 2016 energy code compliance
- Blueprint Newsletter Issue 123 (PDF) — ADUs and adoption of 2019 energy code, effective January 1, 2020
- California Department of Housing and Community Development (PDF) - Information Bulletin providing clarification and outlining provisions of various residential types, ranging from recreation vehicles and manufactured homes to site-constructed California Building Standards Code dwellings.
- For ADUs in Coastal Commission areas:
- ADU guidance memo for planning directors in coastal cities and counties (PDF) - April 18, 2017
- ADU guidance memo update (PDF) - November 20, 2017
- ADU Update: Early Lessons and Impacts of California's State and Local Policy Changes (PDF) – Provides an overview of ADUs as a housing solution for California. Covers recent policy changes at the state and local level, California's progress to date, and remaining barriers. Written by David Garcia at the Terner Center (U.C. Berkeley), December 2017
You'll find additional resources at the following websites, which are hosted by partners who contributed to HCD's Technical Assistance Booklet.
- New! ADU Resource Center the American Institute of Architects (AIA)
- Get Ready for Your Backyard Home San Jose
- The ABCs of ADUs (PDF) – A guide to Accessory Dwelling Units and how they expand housing options for people of all ages (from AARP)
- Clovis Cottage Home Program (PDF) – Promotion of infill residential development on qualified properties in the Old Town area with city provided floor plans, building permit package and fee-waived checked plans
- Lilypad Homes - Resources to facilitate the development of accessory dwelling units that offer a more affordable housing option for both homeowners and renters.
- Accessory Dwellings - One-stop resource about accessory dwelling units. (Portland, OR)
- Everything About Building ADU in Los Angeles - Although the City is still in the process of adopting an ADU ordinance, this fact sheet provides guidance for types of ADU, parking, current building codes, cost estimates, potential rental rates and more.
- Second Unit Resources Center - Although focused on San Mateo County, this website can serve as a great model for other sites. It includes: