ADUs Outpace Single-Family Homes in San Diego

More building permits issued for accessory units than full homes.

It’s taken longer than usual for the Construction Industry Research Board in Sacramento to calculate the annual building permit totals for California’s 58 counties and 538 cities.

For the first time, the board is adding up a separate category for accessory dwelling units (ADUs), also known as Granny Flats.

The results in San Diego County reveal a huge increase in housing construction last year, with a total of nearly 12,000 building permits, a 21% increase over 2022 and the biggest building spree in 17 years, the San Diego Union-Tribune reported.

The lion’s share of permits in 2023 went to multifamily buildings in San Diego County, with 9,100 permits involving apartments, condos and townhouses.

The total number of permits issued for single-family houses in the county was 2,573—a total that includes ADUs. The research board took its time to break out the ADU total because not every city in California has come up with a uniform way to report on Granny Flats, which are usually built in the back yards of houses.

The breakdown between construction of full houses and construction of ADUs in San Diego County reveals the growing popularity of accessory units as a tool to increase housing density in single-family neighborhoods.

According to the research board stats, 1,348 ADUs were built across San Diego County in 2023, while 1,225 single-family homes were constructed. The trending wave of ADUs appears to be growing.

According to the San Diego Association of Governments, the region needs to add at least 20,000 new housing units annually to make up for decades of sluggish building.

Last month, San Jose became the first city in California to embrace a new state law that makes it legal for homeowners to sell ADUs, usually small backyard cottages, as condos separate from the primary house on the property.

San Jose has the final say on whether to allow its homeowners to deploy the new law, which is known as AB 1033 and went into effect in January. AB 1033 gives cities and counties the option of permitting ADU sales.

San Jose’s ordinance allowing homeowners to buy and sell ADUs separately from their primary homes will take effect on July 18.

In 2023, California homeowners added nearly 23,000 ADUs to their property, the most ever in a single year in the Golden State. By allowing these smaller, denser units to be put on the market and traded, the state is hoping to create thousands of new affordable homes.