Accessory Dwelling Unit (ADU) Handbook

Widening the range of housing types can increase the housing supply and help more low-income Californians thrive. Two examples of housing types that can be integrated in existing neighborhoods are Accessory Dwelling Units (ADUs) — also referred to as second units, in-law units, casitas or granny flats — and Junior Accessory Dwelling Units (JADUs).

The California Department of Housing and Community Development (HCD)'s Accessory Dwelling Unit Handbook provides an important resource for understanding:

  • Importance of ADUs in California’s housing landscape
  • Summary of recent changes to Accessory Dwelling Unit laws
  • Frequently asked questions (legislative intent, zoning, JADUs, housing elements, enforcement and other topics)
  • Additional resources

ADUs and JADUs are a flexible form of housing that can help Californians more easily access job-rich, high-opportunity areas. By design, ADUs are more affordable and can provide additional income to homeowners. Local governments can encourage the development of ADUs and improve access to jobs, education and services for many Californians.