When Kol Peterson moved to Portland, Oregon, in 2010, affordable housing was a priority, as it was for many newcomers in this city’s booming real-estate market. He looked at two frequently discussed options for high-cost cities—tiny houses on wheels and communal living—but decided on another option: accessory dwelling units, or ADUs—also known as “granny flats,” or basement or garage apartments.
ADUs weren’t yet common in Portland—that year, the city issued only 86 permits for them—but when Peterson did the math, he decided that building one was his best option. “I could buy a house, construct an ADU in the backyard, and live in the ADU while renting out the house,” he said. That’s what he did: He bought a home in the city’s King-Sabin neighborhood, built a two-story mini-home in its backyard, and moved in. The experience, he says, has been life-changing: “Building an 800-foot ADU eventually eliminated my housing costs, and I’m living in my dream house.”
Eight years later, Peterson works full-time helping others build ADUs and teaching classes for other interested Portland homeowners. The number of ADU permits the city issues has risen dramatically; in 2016, it was 615. In Vancouver, Canada—an ADU pioneer—more than 2,000 ADUs have been built citywide in the last decade. But for most cities in North America, steep legal barriers are preventing this form of housing from taking off: Many cities ban them outright, and those that don’t often have severe restrictions on size, owner occupancy, and parking. Only a handful of cities have adjusted their regulations to encourage more ADUs—mostly on the West Coast, where severe housing affordability is a growing problem. But Peterson and other proponents of ADUs are predicting that the country is on the verge of welcoming more of them.