Seattle City Council votes to reduce barriers to building ADUs


On Monday, the Seattle City Council approved legislation that could make it easier to build accessory dwelling units (ADUs)—like backyard cottages and mother-in-law apartments—along with language that would rein in McMansions in single-family zones.

More specifically: The legislation allows two ADUs on one lot instead of one, and axes a requirement for off-street parking, a sometimes onerous and expensive hurdle for homeowners to jump. Homeowners were previously required to live on the lot containing an ADU in order to rent it out, but the legislation eliminates that requirement, too.

ADUs gain more livable space, too: The ordinance increases maximum ADU size from 800 square feet to 1,000, and slightly increases the allowable height.

It also sets the floor-area ratio (FAR) limit in single-family zones, which limits how much square footage a house can have in relation to its lot, to .5—for example, a single-story house could only have a footprint of half the lot, or a quarter for a two-story house with equal square footage.

City councilmember Mike O’Brien, who represents District 6 on the Seattle City Council and has championed the legislation for years, said in advance of the vote that despite record growth in Seattle’s population, “We’ve seen the population in our single family zoning decline over the years because there’s not really opportunity to add capacity in single family zones.”


While it’s been in the works for longer, the major idea behind ADU reform is around affordability: ADU reform was among the recommendations of the Housing Affordability and Livability committee (HALA) in 2015.

It also paves the way for more homeowners to participate in programs like the Block Project, which builds backyard cottages to house those experiencing homelessness.
The final legislation made some exemptions to the FAR rules. Up to 250 square feet of garage won’t count against it. Neither will up to 35 square feet of dedicated bike parking. Houses that already exist on the lot get a one-time pass to expand up to 20 percent past the limit so as not to step on planned remodels. Basements don’t count either.

Here’s where the ADUs come in: They don’t count against FAR, ideally encouraging more of them to be built.

Single-family zoning in Seattle is currently extremely permissive, and has no FAR limit—essentially, you can build as massive of a home as you want, as long as it’s just one home. This allows one major factor in what’s colloquially known (popularized by Curbed columnist Kate Wagner) as McMansions to thrive: being dramatically out-of-scale with the neighborhood.

This legislation has been in the works since 2014, but it’s been tied up in appeals. Most recently, a city study released back in October was appealed by the Queen Anne Community Council (QACC)—led by Marty Kaplan, a longtime opponent of backyard cottage reform. (The same group was successful in appealing an earlier impact study in 2016.) A hearing examiner cleared the legislation to move forward back in May.

There are a few concerns that have arisen during the heavy public comment around this process, though. The loudest is probably worries about parking impacts—that nixing the off-street parking requirement will result in crowded on-street parking. Other themes include worries about developer speculation in light of removal of the owner-occupancy requirement, and whether the legislation will actually create more affordable housing and not just vacation rentals like those listed on Airbnb.

~Sarah Anne Lloyd, Curbed Seattle


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    Seattle City Council votes to reduce barriers to building ADUs