San Francisco ADUs are being constructed principally within the richest elements of the town

California’s uphill battle against its housing crisis has increasingly called upon a small but powerful actor: the accessory dwelling unit, or ADU.

Often referred to as in-law units or granny flats, traditional ADUs are small dwellings that are located on the same lot as an existing home, and typically have their own kitchens and bathrooms. ADUs can also refer to converted garages, boiler rooms and other sections of apartment buildings turned into housing.

Proponents of ADUs tout them as relatively low-impact tools to both help address California’s housing shortage and to enable lower- and middle-income homeowners to increase wealth and income by renting out the units. State legislators passed numerous laws aimed at making ADUs easier to build in recent years, including one that legalized units on single-family lots in 2020.

San Francisco has enacted numerous pro-ADU laws of its own in recent years as well. In 2016, the city passed Ordinance No. 162-16, which legalized ADU construction across all neighborhoods. It was among the most significant of a handful of pro-ADU policies the city has enacted since 2014, starting with an ordinance that allowed property owners to build ADUs if they also retrofitted their buildings against earthquake damage.

But despite these policies, only 622 ADUs have been built in the city since 2014, representing less than 0.2% of the city’s total housing supply. And those units are disproportionately located in wealthier neighborhoods, a Chronicle analysis has found.

The Chronicle obtained data from the San Francisco Department of Building Inspection on all permitted ADUs completed since 2014, when the city first began enacting ADU-friendly legislation. We then looked at the number of ADUs completed by neighborhood, as a share of each neighborhood’s total housing units.

The majority of ADUs, we found, are being built in neighborhoods in the northern and central portions of the city. The Haight-Ashbury neighborhood has the highest rate of ADU construction relative to its available housing stock; Since 2014, the neighborhood has seen 50 ADUs successfully completed, a rate of 55 per 10,000 existing housing units. Seven neighborhoods, including Sea Cliff and Japantown, have seen zero ADUs, according to the permitting data.

Overall, we found more ADUs built in wealthier neighborhoods — those with higher incomes — than in less wealthy ones.

Our findings dovetail with previous research by a University of Michigan researcher that showed few permits to construct new ADUs have been filed in lower-income communities in San Francisco, and even fewer of those permits have become actual ADUs.

David Garcia, policy director for the Terner Center for Housing Innovation, said that ADUs are being disproportionately constructed in wealthier neighborhoods across the state, not just in San Francisco. “These neighborhoods are (traditionally) housing-exclusive, so I actually think that’s positive,” he said.

However, he said, it is a problem that so few ADUs have been constructed in San Francisco’s lower-income neighborhoods — which he attributes to lower- and middle-income homeowners lacking the cash or equity to pay the often-steep construction and design costs .

“I think we’re used to talking about ADUs being used as tools to build wealth, and if that’s not happening I think that’s a failure of the policy,” Garcia said. He added that the Terner Center and other policy experts are trying to identify possible solutions to the ADU wealth gap, like loans and other financial incentives. Politicians are working on this too: One recent bill introduced by Assembly Member Phil Ting of San Francisco would create a state fund that lower- or middle-income families could draw on to build ADUs.

Other housing experts, though, question whether it’s sensitive for the city and state to spend so much time and energy on ADU legislation at all. Among them is Daniel Parolek, CEO of Opticos Design, a Berkeley architecture firm.

Parolek is also credited with coming up with the “missing middle” concept, or the idea that moderate-density housing options — like duplexes and fourplexes — are key to addressing housing shortages in urban regions like the Bay Area.

“It’s good that we’re adding housing in this way. But a city like San Francisco needs a lot more tools to enable a volume of housing that has an impact,” Parolek told The Chronicle.

He added that in his experience, many California cities are “prioritizing ADUs at the expense of other needed housing efforts,” in part because they’re less politically controversial than other development options, like rezoning neighborhoods or approving large apartment buildings.

And even though San Francisco has passed many recent laws aimed at making ADU construction easier, many builders still see the process as cumbersome, according to Mark Hogan, principal architect at OpenScope Studio. OpenScope helped shape San Francisco’s ADU program and has built numerous ADU projects in the city.

Hogan said this is because the city has its own set of laws around ADUs that are less streamlined than the state’s. For instance, when California legalized ADUs statewide in 2020, it also required local governments to respond to ADU permit applications within 60 days.

But because of a loophole in the law that applies to cities with ADU programs prior to July 2018, including San Francisco, the city doesn’t have to abide by this time limit for ADU permit applications for apartment buildings — the kinds that tend to be most feasible for San Francisco, given that the city’s lot sizes are often too small for the in-law unit type of ADUs. Hogan said this loophole has stalled many ADU projects in larger buildings, frustrating developers.

In 2019, Hogan said, things were looking up for ADU builders when Mayor London Breed issued a directive ordering the Department of Building Inspection to respond to permit applications within four months. But then the pandemic arrived, coinciding with internal department-wide disruptions such as high staff turnover and corruption investigations involving higher-level staff.

“Because of the disruption of staff leaving and the pandemic, that whole four-month timeline has completely gone out the window,” he said.

Susie Neilson is a San Francisco Chronicle staff writer. Email: susie.neilson@sfchronicle.com Twitter: @susieneilson