Encouraging Backyard Cottages

What's Happening Now

On July 1, 2019, the City Council adopted legislation to remove regulatory barriers and make it easier for property owners to create accessory dwelling units (ADUs) and increase the number and variety of housing choices in Seattle's single-family zones. The new regulations will take effect in August 2019.

ADUs include backyard cottages, known as detached accessory dwelling units (DADUs), and in-law apartments, known as attached accessory dwelling units (AADUs). In May 2019, the City's Hearing Examiner upheld our environmental review of the proposal, clearing the way for legislative action on a proposed ordinance. Since 2010, the City has allowed backyard cottages in all single-family zones. To encourage more of this housing type, in 2014 the City Council adopted Resolution 31547 directing us to explore changes that could make them easier to build and allow them on more lots in Seattle.

Project Benefits

Encouraging backyard cottages can increase the supply and variety of housing options in single-family neighborhoods. Backyard cottages share many characteristics with small single-family houses: a single unit with no shared walls in quiet residential neighborhoods. Due to their smaller size and lack of additional land cost, backyard cottages can offer a more affordable housing option in neighborhoods where homes are unaffordable for many people.

Accessory dwelling units also offer a good housing option for various household types, including families with children and multi-generational households. Families can respond to changing needs for living space by adding a backyard cottage or an in-law apartment. Property owners can also rent their ADU to earn additional income that makes it easier for them to remain in their neighborhood.

End Result

Removing regulatory barriers will help property owners permit and construct ADUs, broadening the mix of housing options available in single-family zones.

Environmental Impact Statement

In partnership with the City Council, we completed the environmental review process to study the effects of removing barriers to creating ADUs. In October 2018, the City issued a Final Environmental Impact Statement (EIS). The hearing for this appeal concluded on March 29, 2019. In May 2019, the City's Hearing Examiner upheld the adequacy of our EIS.

Community Meetings

In January and February 2016, we co-hosted two community meetings with Councilmember Mike O'Brien to discuss policy options that could remove barriers to creating backyard cottages and ADUs. Thank you to everyone who attended and shared your ideas and feedback. On the Project Documents page, you can read a summary of what we heard and review our meeting materials.

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Tell Us Your Story

We're interested in hearing about the experiences of those who have built, considered building, or lived near a backyard cottage or ADU. Please contact Nick Welch at nicolas.welch@seattle.gov to tell us your story.

Final Environmental Impact Statement

On October 4, 2018, the City issued a Final EIS analyzing potential environmental impacts of Land Use Code changes related to ADUs. Visit the ADU EIS website to read the Final EIS.

SEPA Draft Legislation

In May 2016, Councilmember Mike O'Brien published draft legislation for environmental review under the State Environmental Policy Act (SEPA), along with the following materials:

Following an appeal of the environmental review, the Hearing Examiner issued a decision directing us to prepare an Environmental Impact Statement (EIS). 

Community Meetings

City Council Lunch and Learn

Reports