Accessory Dwelling Units Code Updates - What & Why

ADU

What Is Happening Now?

SDCI is proposing updates to the Land Use Code for Accessory Dwelling Units (ADUs). The amendments are intended to update regulations for the construction of ADUs required by the state legislature.

Background

During the 2023 session, the state legislature passed House Bill 1337, which requires Seattle and other cities and counties planning under the Growth Management Act (GMA) to meet certain requirements when regulating accessory dwelling units (ADUs). These requirements are codified at Revised Code of Washington (RCW) 36.70A.680 and .681. We are proposing amendments to the land use code for development of ADUs in order to comply with state law.  

Carrying out these state mandates is intended to promote and encourage the creation of accessory dwelling units as a means to address the need for varying and more housing options throughout the city.

This legislation would:

  1. Update provisions related to ADUs, including adding a new code section (SMC 23.42.022) to contain commonly applied standards for ADU development in all zones that allow single-family homes to be constructed.
    1. Eligible zones include: Neighborhood Residential (NR); multifamily (Lowrise (LR), Midrise (MR), and Highrise (HR); Neighborhood Commercial (NC), Seattle Mixed (various SM designations), and downtown (various zones)
    2. Overlay provisions in the Shoreline and historic districts are maintained with no changes
  2. Allow two ADUs to be constructed per lot that contains a principal dwelling unit, which would include the option of developing 2 detached accessory dwelling units (DADUs)
  3. Update standards including height limits, parking, and street improvements
  4. Update provisions related to condo ownership of ADUs

    Project Benfits

    Construction of ADUs has many benefits, including to:

    • Help address the urgent need for housing, including affordable housing, in the city
    • Comply with state law

    The End Result

    These Land Use Code updates will allow for us to meet state law mandates that help address the need for housing in the city.

    Construction and Inspections

    Nathan Torgelson, Director
    Address: 700 5th Ave, Suite 2000, Seattle, WA, 98104
    Mailing Address: P.O. Box 34019, Seattle, WA, 98124-4019
    Phone: (206) 684-8600
    Phone Alt: Violation Complaint Line: (206) 615-0808
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    SDCI issues land use, construction, and trade permits, conducts construction and housing-related inspections, ensures compliance with our codes, and regulates rental rules. SDCI is committed to an antiracist workplace and to addressing racism through our work in the community.