Accessory Dwelling Units EIS

Thank you to everyone who submitted comments on the Draft EIS.

The comment period closed on June 25, 2018. We are now preparing the Final EIS. All comments received will be published in the Final EIS, and a response to all substantive comments will be provided.

The City proposes 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 single-family zones. The proposal involves Land Use Code changes that would allow two ADUs on one lot, modify existing off-street parking and owner-occupancy requirements, change development standards that regulate the size and location of detached ADUs, and that regulate the maximum size of single-family dwellings. Based on a decision from the City’s Hearing Examiner in December 2016, we are preparing an Environmental Impact Statement (EIS) that will analyze three alternatives and identify the impacts of each alternative.

Click below to read more about the ADU EIS:

Draft EIS

Get Involved

UPDATE: The comment period for the Draft EIS closed on June 25, 2018. We are now preparing the Final EIS. All comments received will be published in the final EIS.

Questions? Contact the project team at

What is an ADU?

ADUs are small secondary dwelling units inside, attached to, or in the rear yard of a single-family house. An attached ADU (AADU), often called an in-law unit or a granny flat, is contained within or attached to a single- family house. A detached ADU (DADU), often called a backyard cottage, is a separate structure allowed in the rear yard of certain single-family-zoned lots. DADUs can be new structures or created through conversion of an existing structure, like a garage.

What is an EIS?

An EIS is a tool to inform decision makers about the positive and negative effects of a proposal. The proposal might be a project, like construction of a new building or road, or a new policy or plan that could affect the environment. Washington’s State Environmental Policy Act (SEPA) requires Environmental Impact Statements so that the public, tribes, and other public agencies can help identify a proposal’s environmental impacts, as well as strategies for reducing or avoiding them. Decision-makers can then approve, modify, or deny the proposal as appropriate.


Issue Determination of Significance & Scoping Notice
Determination of Significance and Scoping Notice for the ADU EIS was issued on
October 2, 2017
Conduct SEPA Scoping
The scoping comment period will close at 5:00 p.m. on
November 1, 2017
Extended to November 16, 2017
Prepare Draft EIS
Scoping comments will be reviewed and the Draft EIS will be prepared
Issue Draft EIS
The Draft EIS was issued on May 10, 2018
Draft EIS Public Comment Period
The Draft EIS comment period closed on June 25, 2018.
The DEIS Public Hearing & Open House was on Thursday, May 31, 2018
Hearing location: Seattle City Hall, 600 4th Ave, Bertha Knight Landes room.
Hearing Handout Display Boards Watch Public Comment
Prepare Final EIS
The Final EIS will address comments received during the comment period
Issue Final EIS
Tentative issuance Late Summer / Early Fall 2018
City Action
The City Council will vote on proposed legislation to amend the Land Use Code