San Diego’s Success in Spurring Missing Middle Housing: The Accessory Dwelling Unit Bonus Program

In 2021, San Diego became the first major city in the country to offer a density incentive for accessory dwelling unit (ADU) projects that include new housing deed-restricted to be affordable to lower- and moderate-income households. San Diego’s ADU Bonus Program goes beyond the requirements of state law to allow one bonus market-rate ADU on a given parcel if one additional affordable ADU is added as well, with the option for more ADUs in priority transit corridors.

San Diego’s Success in Spurring Missing Middle Housing: The Accessory Dwelling Unit Bonus Program  highlights the program as a promising example for other California cities aiming to proactively support housing growth, prioritize affordability, and create opportunities for small builders.

While still early in its implementation, we find that San Diego has seen a significant increase in the production of ADUs through its program, particularly in low density, more affluent neighborhoods. The program has unlocked construction on 548 new units of housing. In addition, nearly 300 affordable deed-restricted ADUs were in the process of being built in the first two years of the program, compared to just 7 in the previous two-year period.

Read more for lessons from the program’s implementation.