Op-Ed: Seattle Merely 'Inching Forward' on ADUs

They're a good start. But compared to similar policies in cities like Portland and Vancouver, Seattle's new policies around accessory dwelling units may be lackluster.

1 minute read

October 12, 2018, 7:00 AM PDT

By Philip Rojc @PhilipRojc


Accessory Dwelling Unit

radcliffe dacanay / Flickr

Earlier this month, Natalie Bicknell writes, Seattle released an environmental impact statement proposing the removal of code barriers to the construction of accessory dwelling units (ADUs) and detached dwelling units (DADUs). "The EIS also proposed size restrictions on construction of new single-family homes. Taken together, the two measures are intended to increase and preserve affordable housing stock throughout the city."

While the measure improves on the city's current policies, Bicknell says it does not favorably compare "to Portland's Residential Infill Project, or the more liberal ADU policies of Vancouver." She cites Dan Bertolet's point-by-point rundown of the Seattle plan's strengths and weaknesses, which include a wild card: a so-called "McMansion ban" on new homes that occupy too much of their lots.

Under the new rules, "new homes could be constructed at a maximum of 2,500 square feet or a floor-area ratio of 0.5, or no more the half the square footage of the lot. Considering that in 2018 the average size of a new single-family home in US is 2,641 square feet, with many new homes exceeding that size, the restriction does represent an improvement."

Portland's size restrictions went further, however, also legalizing housing types like duplexes and corner lot duplexes. In other words, missing middle housing.

See also: Portland Makes ADU Incentives Permanent

Monday, October 8, 2018 in The Urbanist

portrait of professional woman

I love the variety of courses, many practical, and all richly illustrated. They have inspired many ideas that I've applied in practice, and in my own teaching. Mary G., Urban Planner

I love the variety of courses, many practical, and all richly illustrated. They have inspired many ideas that I've applied in practice, and in my own teaching.

Mary G., Urban Planner

Get top-rated, practical training

Wastewater pouring out from a pipe.

Alabama: Trump Terminates Settlements for Black Communities Harmed By Raw Sewage

Trump deemed the landmark civil rights agreement “illegal DEI and environmental justice policy.”

April 13, 2025 - Inside Climate News

Logo for Planetizen Federal Action Tracker with black and white image of U.S. Capitol with water ripple overlay.

Planetizen Federal Action Tracker

A weekly monitor of how Trump’s orders and actions are impacting planners and planning in America.

April 16, 2025 - Diana Ionescu

Blue and white Seattle Link light rail train exiting concrete Downtown Bellevue Tunnel in Bellevue, WA.

Why Should We Subsidize Public Transportation?

Many public transit agencies face financial stress due to rising costs, declining fare revenue, and declining subsidies. Transit advocates must provide a strong business case for increasing public transit funding.

April 7, 2025 - Todd Litman

Two people on bikes in red painted bike lane with bus in traffic lane next to them.

Understanding Road Diets

An explainer from Momentum highlights the advantages of reducing vehicle lanes in favor of more bike, transit, and pedestrian infrastructure.

April 17 - Momentum Magazine

Aerial view of large warehouses across from development of suburban single-family homes in Jurupa, California with desert mountains in background.

New California Law Regulates Warehouse Pollution

A new law tightens building and emissions regulations for large distribution warehouses to mitigate air pollution and traffic in surrounding communities.

April 17 - Black Voice News

Purple Phoenix light rail train connected to overhead wires at sunset.

Phoenix Announces Opening Date for Light Rail Extension

The South Central extension will connect South Phoenix to downtown and other major hubs starting on June 7.

April 17 - Arizona Republic