Seattle must legalize more quadplexes and sixplexes under new law

Seattle will eventually have to allow at least four to six units of housing on most, if not all, residential lots.

Driving the news: A new Washington law will require Seattle, as well as other cities with at least 75,000 residents, to allow a minimum of four units per lot in most residential neighborhoods.

• The density requirement jumps up to six units per lot near major transit stops.
• Under the new law, Seattle must make those zoning changes by mid-2025.

Why it matters: Washington is struggling to meet the demand for housing, with state officials estimating 1.1 million new housing units will be needed over the next 20 years to keep up with population growth.

Context: Lawmakers in Olympia this year decided one way to help ease the housing crisis was to require cities to allow denser residential developments in more areas.

• Currently, many neighborhoods have local zoning rules that limit the types of housing that can be built there.
• In Seattle, most neighborhoods are zoned for single-family homes, making it illegal to build fourplexes and sixplexes there — although backyard cottages and mother-in-law apartments can be added in most cases.

Zoom in: A 2021 city analysis found that Seattle had a shortage of about 21,000 affordable housing units, with high rents forcing tens of thousands of lower-wage workers to live outside the city and commute more than 25 miles to their jobs.

What they're saying: "We need more homes in more communities," state Rep. Jessica Bateman (D-Olympia), who sponsored the new state law, said during a recent House floor speech.

Between the lines: The new law would apply to future homes built in residential neighborhoods.

• Still, Seattle Mayor Bruce Harrell is concerned about the potential for longtime residents to be displaced by redevelopment or gentrification, Jamie Housen, the mayor's spokesperson, told Axios.

• Because of that, the mayor's office is looking at an option provided under the law to apply the new density requirements to as few as 75% of the city's single-family lots.
• That could "address the potential need to tailor zoning in areas of high displacement risk," Housen wrote.

Yes, but: Others, including the City Council and state Department of Commerce, would have to sign off on such a plan.

Of note: Under the statewide law, even small Seattle suburbs will have to change their zoning to allow at least duplexes on most residential lots. So will cities with populations between 25,000 and 75,000 across the state.

What's next: Seattle must update its comprehensive plan — a document that sets the city's long-term land use strategy — by the end of 2024 to align with the law's new density requirements.

• Then, the City Council must pass detailed zoning ordinances to implement those changes by June 30, 2025.