Why I’m excited about ADU legislation

I’ve never been able to get that excited about accessory dwelling unit (ADU) legislation. California just passed some bills that legalize backyard cottages/mother-in-law units. These are good things to have and should OBVIOUSLY be legal to build, especially in the midst of a severe housing shortage. 


But they’re hardly going to solve the crisis. We need more apartments! Damn it!

Apartments are the obvious answer to high land costs, which beset California cities. Apartments need less energy to heat and cool, use less water, and more efficient sewer infrastructure. Density makes for walkable, bikeable, human-scale communities. Density in high-growth cities also encourages economic growth and greater economic equality

In a well-functioning market, developers build the most apartments where the rents are highest. So why do California’s most expensive cities, like SF, build the least apartments in the most desirable neighborhoods with the highest land values? NIMBYs, zoning, and permitting bullshit is why. 

Zoning-wise, California isn’t building apartments where they’re needed because municipalities:

  • Limit the number of units allowed per acre
  • Limit allowed building heights 
  • Limit the percentage of land zoned for apartments

It would seem that the way to densify California is to end single-family zoning. But Brookings actually found that in California, increasing the number of units allowed per acre and increasing allowed building heights impacted whether a city got new apartments more than the share of land zoned for apartments. 

The new ADU laws legalize up to two small apartments on every single-family home’s lot, necessarily increasing the number of units allowed per acre. 

Most of California is zoned for single-family homes. While changing that would be excellent, I think ADU legislation might be more impactful than I realized because it vastly increases the number of units allowed per acre throughout the state. And it may be way more impactful than height limits since building taller doesn’t help if you can only build single-family homes. 

Not to mention, Chris Elmendorf recently pointed out on Twitter that “no longer can rich suburbs force newcomers to buy a big dollop of housing as the price of entry.” 

Homeowners support zoning restrictions in part because they don’t want to share schools and other amenities with renters, who are on average lower-income, younger, and browner than the average homeowner.

If the poor, brown children are coming anyway, why not let them live in apartments? 

According to Elmendorf, the new ADU laws legalize one apartment-sized (up to 800 square feet) unit in the backyard and one “junior” unit (up to 500 square feet) which homeowners can carve out of their single-family home. They also waive impact fees for ADUs which are smaller than 750 square feet. Fees for larger ADUs are “proportionate” to the fees charged for new single-family homes. 

“The bottom line in all of these changes is that single-family exclusive zoning will be effectively abolished statewide,” Dylan Casey wrote for CaRLA. 

San Jose is interested in building more ADUs. The city is streamlining the approval process and considering partnering with the Housing Trust Silicon Valley to offer loans of up to $20,000 to cover planning and permitting costs for ADU construction for up to 200 San Jose homeowners, which the city would forgive if the homeowners rent the ADU to low-income residents for five years. 

And residents are also on board. In one recent poll, nearly a third of San Jose homeowners said they were interested in building a backyard home or renting out their converted garage or part of their house. 

One way to cut planning and permitting costs is to work with a company like Abodu, a Bay Area startup that sells prefabricated ADUs with preapproved plans for $200,000. In September San Jose gave the company the go-ahead to start installing.

Another way will be to download a free ADU construction plan from the Housing Endowment and Regional Trust of San Mateo County (HEART). They recently received a $296,000 grant to design plans for studio and one- and two-bedroom accessory units homeowners can build alongside single-family homes.

To ensure California cities comply with state law, consider giving to CaRLA. They sue California suburbs who use bureaucratic bullshit to lock a full quarter of the US population out of economic opportunity and resign them to die in their shrinking towns in order to preserve “neighborhood character” for their wealthy homeowner constituents. 

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