Map Of The Week: Grandfathered Housing In Seattle’s Single-Family Residential Zones


A new research product from the Sightline Institute, a local sustainability think-tank, reveals the rich variety of housing that already exists in Seattle’s restrictive single-family residential zones. The map comes amid neighborhood opposition to rezones that will unlock new affordable housing and calls for preserving the “character” of single-family residential areas. To the contrary, Seattle’s low-density neighborhoods already host a diverse array of multi-unit housing, including duplexes, townhomes, and accessory dwellings.

Sightline’s Margaret Morales explains how this situation came about:

Diverse housing choices in Seattle’s single-family zones are largely relics of the city’s zoning history, legacies of a time when flexible residential zoning covered much larger swaths of the city. As single-family zoning spread across Seattle, it quashed housing choices in most neighborhoods. Today, single-family zoning covers more than half of Seattle, excluding parks and rights-of-way, while only about 10 percent of Seattle’s parcel land area (the private land where private owners can build things) remains open to multi-family housing types.

In 2015, the Housing Affordability and Livability Agenda (HALA) Committee recommended changing the zoning to again allow a mix of low-density housing types in single family areas, just as was allowed in the past. But the recommendation was leaked before proper public process and policy refinement could occur. There was so much backlash from homeowners that Mayor Ed Murray mostly quashed the idea before it could get off the ground. We responded to inflammatory and inaccurate coverage of the situation.

Today, a small spark of this idea lives on, with single-family residential areas within urban village boundaries posed to be converted to Residential Small Lot (RSL) or Lowrise (LR), as part of the Mandatory Housing Affordability program. This would allow a greater mix of housing types, including single-family residential dwellings, small cottages, duplexes, stacked flats, and townhouses. The Sightline map shows that, if the conversation can be reopened, there is great potential for multi-family residential development to find a home in the rest of the Seattle that is off-limits to renters and first-time homebuyers.

Multi-unit housing in the heart of the Wallingford neighborhood. (Sightline Institute)

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Scott Bonjukian is a car-free urban designer with a passion for sustainable and efficient cities. With degrees in architecture and urban planning, his many interests include neighborhood design, public space and street design, transit systems, pedestrian and bicycle planning, local politics, and natural resource protection. He primarily cross-posts from his blog at The Northwest Urbanist and advocates for a variety of progressive land use and transportation solutions.

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Roro Secondus

I used to own a home in that mapped area above. For every grandfathered-in MFH unit in Wallingford, there are probably three or four illicit ones. My neighbors on either side of me had non-conforming, off-the-books rentals.

I never understood the backlash against liberalizing mother in laws. MILs are already happening unlawfully with impunity. Only the scrupulous are being hurt by keeping it de jure unlawful.

I should add – one of my family members who shows up at these meetings to protest liberalizing zoning has an unlawful MIL. I am quite certain she sees no hypocrisy there.


I support the expansion of urban village boundaries around major urban village centers, and the modest upzones to RSL within those boundaries. But I’m very skeptical that developers will be building affordable housing in those zones. The more likely result will be $700K-800K town homes, because that’s where the profits are.

I’d be delighted to be proved wrong. It would be wonderful if we could find builders of $350K homes in Seattle, for middle-class families with children, homes +/-1400SF in size. As of now, those families are the “missing middle” in Seattle. Too “rich” for the subsidized housing, but too poor for the marketplace. Today those families are moving to the suburbs.

Patricia Carroll-Crippen

I live in a Seattle SFH neighborhood on a busy 2 lane street and on my block some of the older homes had been remodeled into small apts. There are also many older smaller duplex/triplex and smaller apt. buildings that are modest and affordable. These are the places that do provide density that I hope owners hang onto, to provide for neighborhood livability for all incomes.