Washington House passes bill that would legalize duplexes, fourplexes

The Washington State House of Representatives has passed a bill that would allow for the construction of duplexes and fourplexes in most neighborhoods.

New numbers from the Office of Financial Management (OFM) show the state's population reached 7.8 million last year, and it's expected to reach 9.5 million by 2044. Because of a 2021 amendment to the state's Growth Management Act (GMA), many communities will have to prioritize affordable housing options and incorporate more apartments, condos and duplexes.

According to the OFM, it's estimated that Washington needs to build an additional 1 million homes by 2044 to keep pace with population growth.

Due to the expected population growth, House Bill 1110 was passed in a bipartisan 75-21 vote on March 6.

HB 1110 is aimed at increasing "middle housing" in areas traditionally dedicated to single-family detached housing. Legislators define "middle housing" as "buildings that are compatible in scale, form, and character with single-family houses and contain two or more attached, stacked, or clustered homes, including: duplexes, triplexes, fourplexes, fiveplexes, simplexes, townhouses, courtyard apartments and cottage housing."

In short, the goal of the legislation is to increase housing options that are more affordable to various income levels.

The bill would require cities with populations between 25,000 and 75,000 to allow duplexes in all residential areas. In bigger cities with populations over 75,000, they would have to allow fourplexes.

Several cities — particularly in affluent suburbs east of Seattle — remain opposed, worried about too much growth and not enough parking, among other infrastructure, to keep up with a potential uptick in new residents, the Associated Press reported last month.

In Seattle, most residential areas allow at least three units per lot with significant restrictions following a 2019 change.

The version of HB 1110 that was passed was amended a second time in committee. In the amendment, the fourplex requirement initially applied to suburbs in Spokane and Tacoma, as well as Seattle, but it was changed to just include Seattle. The amendment also changed the threshold for population and proximity to transit in regards to the construction of duplexes vs fourplexes.

A similar bill, HB 1782, was introduced in the 2021-22 legislative session, but it was returned to the Rules Committee for a second reading and was never passed.

HB 1110 will now go before the Washington State Senate.