A typical accessory dwelling unit, or ADU, is small and hidden behind a larger house. But a program in San Diego makes it possible to add several units to a single lot—in some cases even dozens of units.
A number of new projects built under the program, which went into effect in 2021, have eight ADUs per lot. Another development, built behind a larger apartment building, has 36 ADUs. One proposed development includes 148 units, essentially an apartment complex built from ADUs.
“This is an opportunity to unlock some unused square footage for additional units,” says Gary Geiler, assistant director of San Diego’s Development Services Department.
The city, like many, has a housing crisis. This past summer, Zillow ranked it one of the three most expensive cities in the U.S. for renters—with an average rent of more than $3,000 per month—placing it ahead of even San Francisco. To tackle the housing shortage, San Diego needs to be building around 15,000 new units per year, Geiler says. (Last year, only 5,314 new homes were permitted, and the majority were priced at market rates.) The supercharged ADU program, put in place by the city’s planning department, could help.
Under California state law, residents are already permitted to build one detached ADU and one junior ADU (basically a designated residential space of no more than 500 square feet inside a single-family home but with its own entrance). San Diego’s ADU Bonus Program lets property owners add an extra ADU for each unit that they agree to make more affordable. Those units are limited to either moderate-income tenants for 15 years, or to low-income tenants for 10 years.
That means a residential property owner could have at least five units on one lot: the main house or apartment building, a detached ADU, a junior ADU, and two bonus ADUs. In areas near major transit stops, there isn’t a limit on the number of ADUs that can be built, as long as each market-rate ADU is paired with another that’s affordable and meets building codes and local size restrictions. No new parking is required.
Because ADUs go through a streamlined process for permitting—no longer than 60 days—they can be built faster than traditional apartments. A typical multifamily building might require rezoning in some cases, says Andrew Wofford, a graduate student researcher at the Center for Community Innovation at the University of California, Berkeley who has been studying the program. Wofford says that one developer he spoke to wants to build a 126-unit ADU project on an extra-large lot with a single-family house; if it had to be rezoned, the process could take years before breaking ground.
Focusing on ADUs has other advantages, says architect David Pearson, cofounder of PALO, a firm that has been working on multiple new ADU projects in San Diego.
“A key hurdle to overcome is the resource limitation of land,” he says. “Missing middle housing, especially through programs like the ADU Bonus Program, overcome the limitation simply because they are on average smaller projects than large apartment buildings. They can fit in more places with more agility and flexibility to neighborhood concerns than large projects.”
Pearson says that when his firm works on a project, they start by looking at what’s already on the site that has value and makes sense to keep. Rather than demolishing an old house or apartment building to fully replace it, it’s possible to avoid sending construction materials to landfill. “It also retains community character,” he says.
His firm designs what he calls micro villages. “We think of it as the scale of something you might find in old Europe, where you see a building that was built in one century and then another century, and they’re organized around a small alley that may be only 8 or 10 feet wide,” he says. In San Diego, that might mean that an old 1920s development of small courtyard bungalow rentals is connected to four modern units, for example.
Some residents have pushed back on ADU bonus projects. One group argues that the city “essentially upzoned residential neighborhoods without proper public notification,” and that the law is “neighborhood-killing.”
It’s worth noting that property owners already had the right to make buildings that stuck out—if you lived on a block filled with single-story postwar homes and wanted to build a large second-floor addition to your own house, you could. “The presence of the building and [the scale that’s] allowed hasn’t changed,” Pearson says. “What’s changed is, rather than that square feet being devoted to one family, it’s now something that can go to multiple families and help address our housing shortage.”
A similar policy could be useful in other cities with high housing costs. “There are a lot of cities that have this land-use pattern, where you’ve got single-family homes on lots that are 10,000 to 12,000 square feet, and that’s just a big opportunity to get some infill missing middle housing,” Wofford says, contending that other cities would likely want to add caps on the number of units that can be built—maybe two to four bonus units on lots up to 10,000 square feet, and ten units on larger lots. (He also notes that while the larger projects in San Diego have received more attention, most are smaller-scale examples of what he calls adding “gentle density.”)
Before the program went into effect in 2021, income-restricted ADUs in San Diego were rare. Since then, nearly 300 income-restricted ADUs have been built or are under construction. The program isn’t going to solve the housing crisis on its own, but it can be part of a solution. “I think what San Diego has done with ADUs,” Pearson says, “is an innovative way to expand the tool chest.”
San Diego is constructing ADU ‘apartment buildings’ to fight its housing shortage
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06.12.2023
A typical accessory dwelling unit, or ADU, is small and hidden behind a larger house. But a program in San Diego makes it possible to add several units to a single lot—in some cases even dozens of units.
A number of new projects built under the program, which went into effect in 2021, have eight ADUs per lot. Another development, built behind a larger apartment building, has 36 ADUs. One proposed development includes 148 units, essentially an apartment complex built from ADUs.
“This is an opportunity to unlock some unused square footage for additional units,” says Gary Geiler, assistant director of San Diego’s Development Services Department.
The city, like many, has a housing crisis. This past summer, Zillow ranked it one of the three most expensive cities in the U.S. for renters—with an average rent of more than $3,000 per month—placing it ahead of even San Francisco. To tackle the housing shortage, San Diego needs to be building around 15,000 new units per year, Geiler says. (Last year, only 5,314 new homes were permitted, and the majority were priced at market rates.) The supercharged ADU program, put in place by the city’s planning department, could help.
Under California state law, residents are already permitted to build one detached ADU and one junior ADU (basically a designated residential space of no more than 500 square feet inside a single-family home but with its own........
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