Creating Affordable Housing in Seattle

Abstract: Housing affordability is a critical issue in Seattle as the demand outpaces the new housing construction. This research paper examines the effectiveness of Accessory Dwelling Units (ADUs) as a strategy to address Seattle’s housing shortage and affordability crisis. ADUs have popularized following Seattle’s 2019 zoning reforms, which eased restrictions on size, standards, and owner occupancy. This study uses data from the City of Seattle, government reports, and interviews with builders, investors, and homeowners to evaluate how ADUs contribute to housing supply and affordability. ADUs create more housing stock by increasing the density in single-family neighborhoods and offer lower-cost alternatives to traditional homes. Some limiting factors found are high construction and permitting costs because they limit their affordability for lower-income households. While ADUs represent a solution for increasing the housing stock without government expenditure, they alone are not a solution to Seattle’s affordability crisis. The long term solution is densifying Seattle housing and it depends on zoning reform, building cost reduction, and further integration with broader housing policies.