More ADUs Than Single Homes Being Built in Seattle

Since Seattle started permitting accessory dwelling units (ADUs) in 2019, the city has seen a surge in applications for backyard cottages and other ADUs. According to an article by Daniel Beekman in The Seattle Times, “Almost 1,000 ADUs were permitted last year, up from 280 in 2019.”

That number comes from a report evaluating the success of the city’s ADU policy that could serve as evidence for state legislators, who are considering loosening regulations on ADUs and other mid-density housing types statewide. “House Bill 1337 would remove many barriers to ADUs, while Senate Bill 5235 would also remove some. House Bill 1110 would allow duplexes, fourplexes and sixplexes in more areas.” As Beekman explains, “Proponents of those bills can point to ADUs in Seattle as proof of policy decisions boosting a city’s housing supply with diverse choices in popular areas, while skeptics may question how affordable some of the new choices are — or simply object to density in their neighborhoods.”

Washington needs to add 55,000 housing units in the next two decades to meet demand, and proponents of ADUs say they are an effective and affordable option that maintains low density in neighborhoods while adding housing units and giving homeowners an opportunity to earn extra income.

The report notes that ADUs are being built in almost all parts of Seattle, including single-family zones that are otherwise resistant to new housing. “Many new ADUs are being developed in conjunction with new houses in three-unit packages that resemble town houses, the report notes.”

Not all ADUs become long-term housing, however. “The report estimates that 12% of ADUs in Seattle are currently licensed as short-term rentals like those advertised on Vrbo and Airbnb.”