Accessory Dwelling Units EIS

Final EIS Issued

On October 4, 2018, we issued the Final EIS that examines potential environmental impacts of proposed changes to the Land Use Code related to ADUs.  On October 18, 2018, an appeal of the adequacy of the Final EIS was filed with the City of Seattle Hearing Examiner. The timing for a City Council decision on changes to the Land Use Code to make it easier for property owners to create accessory dwelling units is uncertain while the appeal is ongoing. You can find information about the appeal at: https://web6.seattle.gov/Examiner/case/W-18-009.

The City proposes to remove regulatory barriers in the Land Use Code to 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. Based on a decision from the City’s Hearing Examiner in December 2016, we have prepared an Environmental Impact Statement (EIS) that analyzes how the proposed Land Use Code changes could affect the environment.

Read the Final EIS or our one-page summary.

Draft EIS
Scoping
Background

Next Steps

On October 18, 2018, an appeal of the adequacy of the Final EIS was filed with the City of Seattle Hearing Examiner. The timing for a City Council decision on changes to the Land Use Code to make it easier for property owners to create accessory dwelling units is uncertain while the appeal is ongoing. You can find information about the appeal at: https://web6.seattle.gov/Examiner/case/W-18-009.

Questions? Contact the project team at ADUEIS@seattle.gov.

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 basement apartment, 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.

Published on October 4, 2018, our Final EIS includes a Preferred Alternative for Land Use Code changes to remove barriers to the creation of ADUs. The Preferred Alternative resembles legislation that the City Council will review and consider for adoption. Its key features include:

  • Allowing two ADUs on one lot
  • Removing the off-street parking requirement
  • Removing the owner-occupancy requirement and requiring one year of ownership when creating a second ADU
  • Modifying development standards that regulate the size, height, and location of DADUs
  • Increasing the household size limit for a lot with two ADUs
  • Establishing a new limit on the maximum size of single-family dwellings

The Final EIS identifies and describes potential environmental impacts that could result from removing regulatory barriers to ADU production. For more on the environmental review process, watch our What is an EIS? video and read about the State Environmental Policy Act at the Washington State Department of Ecology website.

ADU Final EIS

ADU Final EIS Appendices

Download by Section

Appendices

  1. Analysis of Housing and Socioeconomics impacts
  2. Parking Analysis Methods and Assumptions
  3. Aesthetics Modeling Methods and Assumptions
  4. Draft EIS Comments Submitted via Email
  5. Draft EIS Comments Received at the Public Hearing

Timeline

Issue Determination of Significance and 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 and 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 addresses comments received during the comment period
Issue Final EIS
The Final EIS was issued on October 4, 2018
City Action
On October 18, 2018, an appeal of the adequacy of the Final EIS was filed with the City of Seattle Hearing Examiner. The timing for a City Council decision on changes to the Land Use Code to make it easier for property owners to create accessory dwelling units is uncertain while the appeal is ongoing. You can find information about the appeal at: https://web6.seattle.gov/Examiner/case/W-18-009.

Study Area

Map of the ADU EIS study area