Seattle’s Zoning Reform Could Unlock a ‘Multiplex Boom’

A package of stackable density bonuses could make it easier for developers to build 12-plexes.

1 minute read

October 6, 2025, 9:00 AM PDT

By Diana Ionescu @aworkoffiction


An African American gentlemen walking by the front sidewalk of suburban townhouse with cherry blossom. Colorful red siding duplex with blooming pink flower.

Trong Nguyen / Ahutterstock

A new series of density and height bonuses in Seattle’s comprehensive plan update could unlock a new supply of multiplex apartment buildings of up to 12 units. 

As Doug Trumm explains in The Urbanist, “Builders able to stack incentives could build 12-unit multiplex apartments, in some cases, where formerly just one primary single family home and two accessory dwelling units were allowed.”

Although officials expect townhomes will make up the bulk of new construction, there are now more avenues for developers to take advantage of the incentives and build more units. 

Other changes that could boost housing include density bonuses for three-bedroom units near schools and projects that plant or protect trees. The city also plans to implement a statewide parking reform law two years early.

Friday, October 3, 2025 in The Urbanist

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