The Washington state House of Representatives late Monday passed a bill that would legalize duplexes or fourplexes in almost every neighborhood of every city in Washington, potentially bringing an end to local zoning rules that limit large swaths of cities to only single-family homes.

House Bill 1110 passed overwhelmingly on a bipartisan 75-21 vote.

It aims to increase housing supply and density in cities across the state without increasing sprawl. Supporters say that increasing housing supply is critical to easing the housing crisis that has seen home prices and homelessness climb throughout the state.

“Young people are being priced out of the opportunity for a future,” Rep. Jessica Bateman, D-Olympia, the lead sponsor, said in a floor speech. “They are being priced out of putting down roots. They are being priced out of building equity. They are being priced out of starting a family.”

Opponents argue that zoning and planning decisions are best handled locally, and that the bill would do little to increase the supply of affordable housing.

The bill, which still must pass the state Senate, would not mean the end of single-family-home construction in Washington, but it could, eventually, mean the end of many neighborhoods made up exclusively of single-family homes.

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The state Department of Commerce estimates Washington needs to build an additional 1 million homes over the next two-plus decades to keep pace with population growth. 

The bill was amended on the House floor just before 11 p.m. Monday.

It would require cities with populations between 25,000 and 75,000 to allow duplexes in all residential areas. In bigger cities (those with more than 75,000 people) — or smaller suburbs of Seattle — all residential areas would have to allow fourplexes.

But a section that required areas close to major transit, parks or schools to allow fourplexes in smaller cities and six-plexes in larger cities was dropped, thanks to an amendment from Rep. Tana Senn, D-Mercer Island. And the requirement for fourplexes initially applied to suburbs of Spokane and Tacoma as well, but that was narrowed to just Seattle.

In smaller cities, fourplexes would still be allowed anywhere, if one of the units meets affordable housing requirements, and six-plexes would be allowed anywhere in larger cities, provided two of the units are affordable.

Local control of zoning laws has long been viewed as sacrosanct, and similar versions of the legislation have failed in recent years.

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“We need homes now and we need action now because we’ve seen so much inaction in local communities for so long,” said Rep. Emily Alvarado, D-Seattle.

“You’ve heard the stories, you’ve heard about the affordability issue,” said Rep. Andrew Barkis, R-Olympia, a co-sponsor. “This policy, combined with the other policies we have already passed in this body this session, will help solve the problem that our state faces.”

States have increasingly stepped in to override municipal rules as populations grow and housing stocks fail to keep pace. Oregon eliminated single-family zoning in 2019 and California largely did the same in 2021.

In its first year of existence, California’s law, which allows property owners to build up to four homes on a single-family parcel, was used sparingly, a study from the University of California, Berkeley, found.