Accessory Dwelling Units EIS

The City of Seattle is proposing to change regulations in the Land Use Code to remove barriers to the creation of accessory dwelling units (ADUs) in single-family zones. The proposal involves allowing two ADUs on one lot, removing the existing off-street parking and owner-occupancy requirements, and changing some development standards that regulate the size and location of detached ADUs.

ADUs have been allowed citywide as part of a single-family house or in the backyard of a single-family-zoned lot since 1994 and 2010, respectively. The City’s action would modify the rules that regulate when and where a property owner can create an ADU. The objective of this action is to remove regulatory barriers to ADU production, increase the number of ADUs constructed in Seattle, and allow flexibility for larger ADUs that could accommodate changing household needs and families with children. These policy changes would affect development in Seattle’s single-family zones.

Based on a decision from the City’s Hearing Examiner in December 2016, we are preparing an Environmental Impact Statement (EIS) that will analyze two alternatives and identify the impacts of each alternative. We want your feedback on what to consider and analyze as we explore small-scale housing options in Seattle’s neighborhoods.

Get Involved

Comment on the proposed EIS scope
  • Online comment form
  • In writing at the EIS Public Scoping Meetings/Open Houses:

      • October 17, 2017, 6:00-7:30 p.m. Location: High Point Community Center, 6920 34th Ave SW, Seattle, WA 98126
      • October 26, 2017, 6:00-7:30 p.m. Location: Hale’s Ales (in the Palladium), 4301 Leary Way NW, Seattle, WA 98107
    These meetings will provide an opportunity to learn more about the proposed land use code changes and provide input on the environmental review process.
  • Via e-mail to: ADUEIS@seattle.gov
  • In writing to: Aly Pennucci, PO Box 34025 Seattle, WA 98124-4025
 

What is an ADU?

ADUs are small seconary 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.

What is Scoping?

At the start of the EIS process, we invite the public to comment on what we should study during a specific scoping period. The scoping period alerts us to areas of concern early in the process. During this period, the public helps us identify topics that need the most thorough review and the range of issues we should study.

The Washington State Department of Ecology also has information about SEPA and the EIS process at www.ecy.wa.gov/sea/sepa/e-review.html.

Timeline

Issue Determiniaton 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
Prepare Draft EIS
Scoping comments will be reviewed and the Draft EIS will be prepared
Issue Draft EIS
Tentative issuance Spring 2018
Draft EIS Public Comment Period
A 30-day comment period will follow the issuance of the Draft EIS and will include a public hearing
Prepare Final EIS
The Final EIS will address comments received during the comment period
Issue Final EIS
Tentative issuance Summer 2018
City Action
The City Council will vote on proposed legislation to amend the Land Use Code

Comparison of Alternatives

At the start of the EIS process, we invite the public to comment on what we should study during a specific scoping period. The scoping period alerts us to areas of concern early in the process. During this period, the public helps us identify topics that need the most thorough review and the range of issues we should study.

Alternative 1 (No Action)Alternative 2
1 Number of ADUs allowed on a single-family lot

A single-family lot can have one AADU or one DADU, but not both.

A single-family lot can have an AADU and a DADU.

2 Parking

One off-street parking space required for an AADU or DADU unless the lot is in an urban village.

No off-street parking required.

3 Owner-occupancy

An owner must occupy either the main house or the AADU/DADU 6 months a year.

No requirement for an owner to occupy the house, AADU, or DADU.

4 Minimum lot size for a DADU

4,000 square feet

3,200 square feet

5 Maximum square footage

AADU 1,000 square feet, including garage and storage areas

DADU 800 square feet including garage and storage areas

AADU 1,000 square feet, excluding garage and storage areas

DADU 1,000 square feet, excluding garage and storage areas

6 Maximum height

No change from existing height limits, which vary by lot width and range from 15-23 feet.

Height limits are 1-3 feet higher than existing limits, depending on lot width.

7 Lot coverage limit

35 percent of lot area for lots 5,000 square feet and larger and 15 percent of lot area plus 1,000 square feet for lots under 5,000 square feet.

8 Rear yard coverage limit

40 percent of a rear yard can be covered by a DADU and other accessory structures (like a garage). This limit applies in addition to the overall lot coverage limit.

60 percent of a rear yard can be covered by a DADU and other accessory structures, if the DADU is only one story and if rear yard coverage from other accessory structures is less than 40 percent.

9 Location of entries

DADU entrances cannot face the nearest side or rear lot line unless that lot line abuts an alley or other public right-of-way.

DADU entrances can be on any façade, provided it is 10 feet from the lot line if located on the façades facing nearest side or rear lot line (unless abutting right-of-way).

10 Roof features

No exceptions from the height limit are allowed for roof features on accessory structures.

Exceptions from the height limit are allowed for projections like dormers that add interior space, subject to the provisions applicable to single-family houses.

11 Household size

Any number of related people, or up to 8 unrelated people, can live on a single-family lot, including in an AADU or DADU.

Any number of related people, or up to 8 unrelated people, can live on a single-family lot with an AADU or DADU. If the lot has an AADU and DADU, the limit is 12.

12 MHA requirements

Mandatory Housing Affordability (MHA) does not apply to creation of ADUs in Single Family zones.

13 Rental Registration & Inspection Ordinance (RRIO)

Property owners renting one or more units, including in Single Family zones, must register for inspections to ensure housing is safe and meets basic maintenance requirements.

Proposed Scope

The EIS will incorporate information and analyses from the Mandatory Housing Affordability (MHA) EIS (2017), the Seattle 2035 Comprehensive Plan EIS (2016), the Growth and Equity Analysis (2016), and other recent City studies and plans.

In December 2016, the Seattle Hearing Examiner determined that a thorough review of the proposal’s potential environmental impacts through an EIS was necessary. Based on this decision, we have preliminarily identified the following elements of the environment for analysis in the EIS:

Land Use

  • Compatibility of alternatives with Single Family zoning
  • Potential elimination of existing housing
  • Potential impacts on vegetation, tree canopy, and environmentally critical areas (ECAs)

Housing & Socioeconomics

  • Feasibility of development scenarios
  • Housing affordability
  • Assessment of socioeconomic characteristics, demographic change, and potential displacement

Aesthetics

  • Potential impacts to visual character
  • Qualitative review of shadowing, privacy, scale, and compatibility with single-family development

Transportation

  • Potential impacts to availability of on-street parking
  • Assessment of car ownership rates, transit, and circulation patterns

Public Services & Utilities

  • Police, fire and emergency services, public schools, water, sewer, stormwater
  • Potential impacts on demand for services in each alternative

Scoping Comment Form

The City of Seattle is proposing to change regulations in the Land Use Code to remove barriers to the creation of accessory dwelling units (ADU) in single-family zones. The proposal involves allowing two ADUs on one lot, removing the existing off-street parking and owner-occupancy requirements, and changing some development standards that regulate the size and location of detached ADUs.

We are preparing an Environmental Impact Statement (EIS) that will analyze two alternatives and identify the impacts of each alternative. We want your feedback on what to consider and analyze as we explore options for small-scale housing options in Seattle’s neighborhoods. Complete this comment form at the October 17 or October 26 public meetings or submit your comments by November 1, 2017, at 5:00 p.m.

All comments are welcome during the scoping phase, but comments on the following topics are particularly valuable:

  • Reasonable range of alternatives
  • Potentially affected resources and extent of analysis for those resources
  • Measures to avoid, minimize, and mitigate effects of the proposal

Resources

Scoping Handout

Scoping Meeting Boards