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Built by Blue Sound Construction, designed by MaKe Design, photos by Alex Hayden

Final Environmental Impact Statement on Seattle’s Proposed ADU Ordinance Released

Posted on Oct 5, 2018 in:
  • Industry Issues
  • Building Codes
  • Advocacy

The Final Environmental Impact Statement (FEIS) analyzing three alternatives and Council’s preferred alternative for adopting a proposed Attached Accessory Dwelling Unit (AADU) and Detached Accessory Dwelling Unit (DADU) ordinance, was released on October 4, with a determination of no significant impact. Some highlights of the preferred alternative include:

  • Lots in single family zones can have an AADU and a DADU or two AADUs. A second ADU can be added if a lot has been in the same ownership for at least one year.
  • No off-street parking requirement.
  • No requirement for the owner to occupy the house, AADU, or DADU, however, a minimum of one-year continuous ownership is required to establish a second ADU.
  • New houses (principal structures) are subject to a FAR limit of 0.5 or 2,500 square feet, whichever is greater. Below-grade floor area and floor area in an ADU is exempt.
  • Floor area limits of existing housing on existing lots in single-family zones exceeding the FAR or 2,500 square feet limits can convert existing space to an AADU and add a DADU, subject to the size limit.

With opponents signaling they plan to file an appeal, next steps remain uncertain. However, your association has already begun to advocate for changes and modifications to the preferred alternative while urging support for other provisions.

Contact King County Manager Gina Clark, 425.460.8203, with questions.


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Photo courtesy Blue Sound Construction, builder; MaKe Design, architect; and Alex Hayden, photographer