California Department of Housing and Development

The ADU Revolution Has Begun

  • The number of ADU permits issued across CA increased from almost 6,000 in 2018 to almost 16,000 in 2019. Altogether, almost 9,000 ADUs were built in 2018 and 2019.
  • A majority of CA jurisdictions (87%) have adopted at least one ADU ordinance, and many regions with high rates of ADU ordinance adoption also built a large share of ADUs between 2018-2019.
  • Approximately 86% of both the general public and elected officials are supportive of the state-level ADU legislation.
  • ADU production is generally occurring in diverse, transit-accessible neighborhoods where a greater share of homeowners have recently purchased their homes and still have a mortgage.
  • Overall, 92% of ADUs are built on parcels zoned for single-family residential, but about 2% are being built on lots with duplexes, triplexes, or fourplexes, suggesting that the move to build missing middle housing has already begun.
  • Almost 70% of ADUs are built on parcels where the main house has 3 bedrooms or more, suggesting that lack of space is not the primary motivator.
  • Over 3,300 ADUs have been built on parcels of less than 5,000 square feet, proving that eliminating minimum lot sizes has had a meaningful impact on state housing production.