Proposed bill released to encourage construction of Backyard Cottages

Last week, Councilmember Mike O’Brien released a proposal that would make it easier for more homeowners to build backyard cottages and mother-in-law units in Seattle.

According to O’Brien, as of December 2015, 221 backyard cottages had been constructed or permitted in Seattle since Council authorized their use in 2009, despite approximately 75,000 single-family lots that are eligible to build one.

Backyard cottages, also called detached accessory dwelling units (DADUs), are separate living spaces on the same property as an existing single-family house. Mother-in-law units, also referred to as accessory dwelling units (ADUs), are separate living units generally located within a single-family house. Both are currently allowed in single-family zones.

Councilmember O’Brien heard feedback that current regulations put significant burdens on homeowners deciding to build backyard cottages or mother-in-law units.

The proposed bill makes a series of changes to the existing backyard cottage and mother-in-law unit building code, including:

  • Allowing both a backyard cottage and mother-in-law unit on the same lot, which provides additional housing options while maintaining the character and appearance of the property.
  • Increasing the height limit for backyard cottages by 1-2 feet, depending on lot width, which would allow enough livable space to make two-bedroom units more feasible. Setback requirements from property edges would not change.
  • Removing the requirement for owners to include an off-street parking space for backyard cottages or mother-in-law unit. Currently, this requirement often requires removal of green space on the property. Feedback found the parking requirement was prohibitive in creating new backyard cottages, as additional parking spaces were either unnecessary or unable to fit on the lot. For single-family lots outside urban villages or urban centers, the one required off-street parking space for a single-family house requirement will still apply.
  • If a backyard cottage is only one-story, its floor area may cover up to 60% of the rear yard (currently 40%), creating a large enough livable space for those unable to use stairs. Existing setback requirements from the lot edge would not change.
  • Requiring that the property owner live on-site for at least one year after a backyard cottage or mother-in-law unit is created, rather than the current requirement that the owner live on-site at least 6 months out of every year in perpetuity. The requirement prevents speculative developers from acquiring property and building backyard cottages that don’t fit the character of the neighborhood, while allowing the owner future flexibility for those who don’t want, or are unable to continue living on-site.
  • Allowing backyard cottages on lots 3,200 square feet or greater in area (currently 4,000 square feet), which would make approximately 7,300 additional parcels eligible to provide this additional housing option.
  • Increasing the maximum gross floor area of a backyard cottage to 1,000 square feet (currently 800 square feet), which would provide more livable area and increase the likelihood of two-bedroom backyard cottages to better serve families with children.
  • If a backyard cottage is built above a garage, the garage square footage will no longer count toward the maximum floor area, which often results in an unreasonably small living space.
  • Additional changes can be found here.

“By expanding the availability of backyard cottages and mother-in-law units, someone might be able move to a neighborhood they otherwise couldn’t afford while helping a homeowner who needs an extra source of income to afford to stay where they are.  It’s a win-win,” says Councilmember O’Brien.

The legislation was developed utilizing feedback from neighborhood community meetings, from architects, and from current backyard cottage owners. A summary of the public feedback is available online. The Office of Planning & Community Development, also conducted an analysis of current backyard cottages in Seattle and a review of peer cities’ backyard cottage model.

“After reading the new proposed changes for backyard cottages, there are definitely some new rules which would have greatly benefited this particular project,” says Janice Reebs, a backyard cottage owner in the Sunset Hill neighborhood.

The SEPA environmental determination on the draft proposal was published May 19, 2016. Comments may be submitted through June 2, 2016.

The proposal is scheduled for consideration in the Council’s Planning, Land Use & Zoning Committee in July.

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