This is why you should build an ADU in Seattle right now

Seattle is experiencing a significant shift in its housing landscape, with Accessory Dwelling Units (ADUs) emerging as a key solution to the city's housing challenges. These secondary housing units, including Detached ADUs (DADUs) like backyard cottages and Attached ADUs (AADUs) such as basement apartments, are gaining popularity among homeowners and city planners alike.

Designing and Building an ADU Just Got Easier

Back in 2019, Seattle made key changes to its zoning and permitting rules that made it easier—and more appealing—for homeowners to build ADUs. These reforms included:

• Allowing two ADUs per lot instead of just one (for example, a basement apartment and a backyard cottage on the same property).
• Removing the owner-occupancy requirement, meaning the property owner no longer has to live on-site, which helps with long-term flexibility.
• Eliminating off-street parking requirements for ADUs, lowering construction costs and simplifying design.

Since then, ADUs have steadily grown in popularity across the city. Over the past five years, more and more homeowners have taken advantage of these opportunities to create rental units, multi-generational living spaces, or future downsizing options—often without leaving the neighborhood they love.

Benefits of ADUs

ADUs offer numerous advantages:

• Affordability: They provide more affordable housing options in high-demand neighborhoods.​
• Flexibility: Homeowners can use ADUs for rental income, housing family members, or downsizing.
• Sustainability: ADUs increase housing density without significantly altering neighborhood character.

Designing Your ADU

As architects, we’re seeing a strong interest in designing ADUs that blend seamlessly into existing homes and neighborhoods. Good design is key—whether you’re working with a compact backyard, a sloped lot, or a tight budget.

We help homeowners navigate zoning, permitting, and design to make the most of their property. Every lot is different, and the right ADU solution depends on your goals—whether it's passive income, downsizing, or creating space for extended family.

For homeowners considering an ADU project, now is an opportune time to explore the possibilities and contribute to Seattle's evolving housing landscape.