Installing an Accessory Dwelling Unit in Seattle, WA

Always a city to lead the charge on new ideas, in July 2019, Seattle Mayor Jenny Durkan signed legislation to remove regulatory barriers for accessory dwelling units. This new legislation made it easier for property owners to construct ADUs in Seattle’s single-family zones and incorporated a size limit on new homes being built. At the time, these new laws were among the most progressive ADU policies in the United States. This legislation allows for two ADUs per lot and one DADU (Detached ADU) per lot. The only other city that allows that in North America is Vancouver, British Columbia. This flexibility maximizes the opportunities for those who own smaller, less expensive homes. These laws are significantly important for a city like Seattle, where going green is the goal, and the unhoused population has grown by 30% since 2010 in King County, according to the Seattle Times. Learn how ADUs can assist with these issues and how you can build an ADU in your Seattle yard with help from Abodu.

Accessory dwelling units are allowing Seattle to increase the supply of housing options for single-family neighborhoods. Because of their smaller size and lack of cost for additional land, ADUs offers a more reasonably priced option for housing in communities where the price of building a home is out of reach for many residents. Lawmakers hope this is a big step in addressing Seattle’s housing crisis. Additionally, ADUs offer support for older adults looking to downsize, lower and middle-income households, property owners with disabilities, and multigenerational families. These backyard dwellings can also provide additional income to homeowners who use their ADU as short-term or long-term rental space.

– Parking is no longer required for accessory dwelling units. However, laws prohibit the removal of existing required off-street parking unless replaced somewhere else within property lines.

– The property owner is not required to live on the property they are constructing an ADU on.

– All accessory dwelling units permits need to be reported to King County for sewer treatment capacity charges. Property owners will have to fill out a form acknowledging capacity charges during their application process.

While Seattle has some of the most progressive ADU laws in the nation, some improvements could be made that could make the process even better. Those additional steps include:

– Remove the minimum lot size requirement

– Eliminate the occupancy limits based on legal relationship status

– Reduce utility and permitting connection fees

– Eliminate any requirements that state second ADUs must either be reserved for income-eligible households or meet a green building standard

– Allow residents the option for two backyard cottages, detached or attached to each other