Installing an Accessory Dwelling Unit in Seattle, WA

Abodu Unit


December 7, 2021Backyard Living

Seattle offers some of the most progressive ADU laws in the nation. Learn how Abodu can help you construct an ADU In Seattle, Washington. 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.

Pre-Approved DADU Plans

In September of 2020, the Office of Planning and Development (OPCD) launched the ADUniverse website. This site provides residents with pre-approved DADU (detached additional dwelling unit) designs and a step-by-step guide to the accessory dwelling unit process. The city offers ten pre-approved unit plans and has enabled citizens to construct their units faster and easier than in the past. The average time to get a permit in Seattle is 8-10 weeks. This website is the central source for Seattle residents looking to put an ADU on their property. Along with Seattle’s newly constructed laws, this website helped Seattle’s ADU production increase to its highest level in history. From 2019 to 2020, Seattle issued 237 AADU permits and 276 DADU permits, making for an 80% increase since 2019.

Why Is Seattle Encouraging ADUs?

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.

What Are Some Of the Requirements to Build an ADU in Seattle?

– Seattle law states that in the city’s SF5000, SF7200, and SF900 zones, as many as two ADUs may be built. The property owner has the choice to either construct two AADUs (attached accessory dwelling unit) or one AADU and one DADU. In order to be constructed, the second unit must either 1) meet green building standards or 2) be reserved for income-eligible households. In RSLs (residential small lots) and multifamily low-rise zones, a singular detached or attached ADU is permitted for each row house, single-family home, or townhouse. Additionally, accessory dwelling units are allowed in apartments in RSL zones but not in low-rise zones. – 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.

What Else Seattle Could Do to Improve ADU Laws?

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

Construct your Seattle ADU with Abodu

For those looking to construct an ADU in Seattle, Abodu can make the process simple and help inspire you to rethink your yard’s potential. Our goal is to go above and beyond the regular ADU experience. By partnering with world-renowned architects, we have created beautiful spaces with enough custom design elements to allow you to bring an individual touch. From our studio unit to our two-bedroom option, Abodu offers pre-designed units of varying sizes that can fit anyone’s needs. For more information on the Abodu experience, visit our showroom or fill out our contact form today. Share on facebookShare on Twitter(

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