After half a decade of planning, changes to laws governing backyard cottages are on the way

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.”

“What are we going to do with our single family neighborhoods?” asked O’Brien. “Who has access to those, and who is locked out?”

“This legislation creates modest but meaningful changes to provide flexible, affordable housing options for families, homeowners, and renters while still preserving the look and feel of single-family neighborhoods,” O’Brien added in an emailed statement after the vote.

“We think that in general this is an important point of change,” said Matt Hutchins, representing AIA Seattle, during public comment. The organization strongly supports the legislation.

Hutchins added that the legislation is critical in “deciding who gets to live here and how, and what our neighborhoods look like.”

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.

A Block Project home—a backyard cottage providing permanent housing for someone experiencing homelessness—being constructed.

Courtesy of King County

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.

The City Council is also going to get annual reports from the Seattle Department of Construction and Inspections (SDCI) on the impacts of the legislation, including the number of permits issued, geographic data, and parking impacts.

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.

Speaking to City Council during the public comment period, Kaplan said the legislation “favors uncontrolled development of market-rate [duplexes and triplexes] by developers and speculators,” calling the bill a “wholesale conversion of our single-family neighborhoods.”

Referring to similar allegations “in print media,” councilmember Lorena González said the legislation is not a dramatic zoning change: “That kind of rhetoric doesn’t make it true just because you keep saying it.”

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.

As for the parking: While council kicked around an idea to require off-street parking for a second ADU, that ultimately didn’t pan out. However, the legislation mandates a parking report as part of SDCI’s annual presentation, including recommendations for needed modifications—which could be geographically specific if necessary.

O’Brien told us in early May that two- and three-unit projects aren’t particularly enticing to real estate investors: “What the analysis showed was, no, that’s not actually going to happen,” he explained. “It’s not a viable economic model ... but we are seeing a lot of developers tear down single family homes, and what they build is a bigger single family homes. And if we want to encourage folks to not do that and instead maintain existing family homes and build backyard cottages or in-law units.”

One real estate investor did get up to speak and noted that investors are already looking at properties, but didn’t provide any specifics. Investment in ADU properties isn’t unheard of, although, as councilmember Teresa Mosqueda pointed out, it hasn’t been the case in Portland, which has no owner-occupancy requirement for ADUs.

“The data shows… that overwhelmingly two thirds of [homeowners] who currently have a backyard cottage in Portland have lived in their primary residence… for more than five years,” said Mosqueda in advance of the vote. 95 percent of Portland homeowners who built an ADU, she added, have lived in the property for more than one year.

This data is consistent with a 2018 study from Portland State University, which also found that 41 percent of homeowners with an ADU have lived there for more than a decade.

Besides, O’Brien pointed out, with the owner-occupancy requirement, if the homeowner has to move they have to kick out a tenant.

Councilmember Lisa Herbold wasn’t convinced, and presented an amendment, originally floated in committee, that would require a watered-down kind of owner occupancy—homeowners would have to live on the property for at least one year before building a second ADU.

An ADU by Node recently constructed in a West Seattle backyard.

Andrew Pogue/Courtesy of Node and Wittman Estes

“We don’t know what’s necessarily going to happen in this housing market, and we can’t prevent speculative development,” said Herbold while presenting the amendment, “but this creates a speed bump.”

Councilmember Abel Pacheco said he shared Herbold’s concern, but cited a lack of data to back it up. He noted that the annual report from SDCI would be a good opportunity to keep an eye on it.

That owner-occupancy amendment overwhelmingly did not pass.

Relatively new requirements to regulate and tax short-term rentals opens the door to analysis of ADUs used as vacation rentals, too. The legislation directs the Seattle Department of Finance and Administrative Services to work with SDCI to evaluate how many ADUs are short-term instead of long-term rentals and make recommendations for changes to the law. If a “significant number” of those ADUs are being used as vacation rentals, the bill reads, “the City Council intends to impose additional restrictions or a prohibition on short-term rental use in [ADUs].”

In Portland, the same PSU study found, around a third of ADUs are being used as short-term rentals.

One limitation that Mosqueda acknowledged: It’s still expensive to build housing, between permitting and utility fees. AIA Seattle in particular, she said, has called for a policy to make permitting easier. “I’m going to commit to you to keep working on this,” said Mosqueda.

Councilmember Kshama Sawant expressed interest in looking into public financing for homeowners that can’t afford to build an ADU.

A couple of speakers during public comment claimed the legislation would have a negative effect on the tree canopy. Former councilmember Rob Johnson heralded an effort to strengthen Seattle’s tree protection ordinance last year, but its future is unclear after Johnson’s resignation. O’Brien clarified before the vote that there’s no change to lot-coverage requirements and current tree regulations are “largely in place,” although they could use updates.

The bill’s next stop is Seattle Mayor Jenny Durkan’s desk. If signed, the changes would be in effect in 30 days, except for the FAR piece, which would take effect in six months.

“ADUs and DADUs provide opportunities for multigenerational housing, help us decrease our environmental and carbon footprint, and provide some homeowners with a way to stay in their homes and age in place—an important benefit as the cost of living rises in Seattle,” said Mosqueda in a statement after the bill’s passage. “This is one meaningful step that will generate gentle infill housing options, but much more must be done to create the density we need to accommodate our growing city.”

This article has been updated with information on ADU size and statements from councilmembers O’Brien and Mosqueda, and to note McMansion was recently popularized—not recently coined.