What is an Accessory Dwelling Unit?
Accessory Dwelling Units (ADUs), sometimes called secondary units, granny units, in-law units, and backyard cottages, are self-contained residential units located on the same lot as, but separate from, the primary unit, with a separate entrance, kitchen, and bathroom. ADUs can be either attached or detached from the main dwelling, and are sited in a manner that preserves the single-family nature of a neighborhood. A junior ADU (JADU) is an ADU typically attached to or built within the footprint of the primary residence and does not include complete facilities (e.g., less than a complete kitchen).
The Housing Trust Silicon Valley has developed an ADU financing program, which provides free informational workshops to interested homeowners, and a loan program to encourage ADU production throughout Santa Clara County. The loan program covers detached ADUs and garage conversions, and requires that a homeowner agree to a 2-year affordability restriction: ADUs built with the loan must be rented to a low-to moderate-income household for at least two years. As financing can otherwise be a major hurdle, having a consistent resource in the region can assist many homeowners in reaching the finish line of their ADU projects. Learn more about the Housing Trust’s Small Homes, Big Impact program.
By State law, ADUs are allowed in all cities in California. Recent changes to State law, established by a series of bills including SB 1069 (Wieckowski, 2016) and AB 2299 (Bloom, 2016) have required local jurisdictions to ease certain zoning regulations to support the creation of ADUs. Most cities in Santa Clara County updated their ordinances to comply with the new law.
In the four years after the passage of these bills, the number of ADUs permitted permits in Santa Clara County have been steadily increasing, as shown in the table below (with a slight decline from 2019 to 2020, during the COVID-19 pandemic).
|Jurisdiction||2017||2018||2019||2020||Total||% of Countywide Total|
|Los Altos Hills||7||26||8||25||66||2.9%|
SV@Home’s Position: We Need New and Innovative Housing Solutions
SV@Home is working to promote policies and implementation actions that increase the number of lots that could qualify for a second unit and that provide flexibility and simplicity for homeowners, including provision of technical assistance and support.
Our policy recommendations for second units focus on:
- Simplifying and easing development standards: reducing or eliminating minimum lot size requirements to increase the number of properties where second units can be built.
- Eliminating fees: removing fees decrease overall project costs, allowing more property owners to take advantage of simplified development standards
- Amnesty: enabling amnesty for units that were illegally built as long as they are brought up to current building codes.
- Housing Trust Silicon Valley Small Homes, Big Impact: Highlights of 2019 ADU Workshop 2019
- AARP: The ABCs of ADUs 2019
- Home For All San Mateo County & 21 Elements: Second Unit Resource Center & Cost Calculator
- California Department of Housing and Community Development: Accessory Dwelling Units (ADUs) and Junior Accessory Dwelling Units (JADUs) (2021)
- Terner Center for Housing Innovation: Reaching California’s ADU Potential: Progress to Date and the Need for ADU Finance (2020) & First Ever Statewide ADU Owner Survey Shows Growth, Room for Improvement (2021)