June 10, 2025

Shared spaces make housing affordability a reality in Seattle’s single-family zones

Martin

When Barbara Busetti and I founded Allied8 in 2015, we made a promise to each other to develop something different. Our development couldn’t just be run-of-the mill, but rather, it had to be something that served as an example of how a small firm could contribute to housing affordability in Seattle and elsewhere. We set our sights on single family zones (now called Neighborhood Residential in Seattle) and more specifically, on building affordable homes in single family zones.

Our premise was very simple — the average size of a home in Seattle is 2,600 square feet and costs over $900,000. If that average home could be divided by three owners, then theoretically each owner would be allotted 860 square feet, and it would cost them $300,000 each.

To do that in a way that people would want to purchase a part of a home that also complied with Seattle’s Zoning code, meant Allied8 had to create a new housing typology that didn’t otherwise exist on the market, and it would have to rely on the fact that people would be willing to share certain spaces within their home.

Photo by Rafael Soldi [enlarge]

Homeowners at Corvidae Co-op in Columbia City share outdoor, kitchen, dining, laundry and guest space.

Allied8 got to work! We drew, we interviewed hopeful first-time home buyers, we drew more, we created construction budgets, we kept drawing, and then we bought a property. Out of this effort, the “suite” was born and is on full display at Corvidae Co-op in the Rainier Valley, a co-development between Allied8 and Frolic Community.

Before we share the anatomy of a “suite,” we need to provide the affordability context of the current and planned zoning codes. As the Seattle zoning code is currently written, NR zones can accommodate a single-family residence and two accessory dwelling units. The single-family residence (SFR) is allowed to be 50% of the lot area.

On a commonly sized lot of 5,000 SF, the SFR would be 2,500 SF. Per Redfin, the median sale price per square foot (for single family homes) in Seattle is $592.

There are no affordable homes on the market in Seattle because of this — check out the math: 2,500 SF X $592/SF = $1.48 million home.

For those of you familiar with affordable homeownership math, a four-person household that could afford this home would make 219% of the Area Median Income (AMI). Affordability is defined as a household earning 80% AMI or less. The gap between 80% AMI and 219% AMI is staggering. It’s no wonder we’re in the midst of an affordable housing crisis.

Looking ahead to the Seattle One Plan, which reflects the increased density mandated by the Washington State House Bill 1110, Seattle’s planned zoning code will allow four units on a lot.

The math is better, but it still doesn’t reach affordable levels. On that same 5,000-square-foot lot used in the math above, four 1,500-square-foot homes would be allowed, but each home would still cost $888,000. A four-person household that could afford this home would have to make 136% of the Area Median Income (AMI). The gap is still too large to provide affordable homeownership solutions in NR zones.

But imagine if two households could own one of those homes — that’s where affordable levels begin to be met. The challenge is to design homes that thoughtfully accommodate shared ownership among different households.

THE ANATOMY OF THE “SUITE”

Image courtesy of Allied8 [enlarge]

Corvidae Co-op uses single family zoning creatively to spread10 individually-owned residences over two lots.

A conventional dwelling unit contains rooms we use every day and rooms that we may only use once a week, once a month or less. The “suite” distills the dwelling down to only the rooms and features that are used on a daily basis. Rooms and features that are used less frequently are pulled out of the private dwelling and placed in the communal space, making the “suite” more affordable than a conventional dwelling unit because an owner is paying a privacy premium only on what is used every day, and the rest is split amongst all the other owners.

Additionally, we have proven that people want more choice than what is on the market. Corvidae sold out its “suites” before it sold out its conventional units. We now have six comps that future projects can utilize for loan underwriting and appraising.

The market is undeniably there.With 366,000 renters, Seattle now has more renters than homeowners for the first time in more than 100 years, according to a 2021 Seattle Times article. If only 10% of that population wanted to own a home in Seattle (we believe the number is much higher), then the market for “suites” is robust.

“Suites” are a powerful tool that enable architects and developers to introduce affordability into neighborhoods that have been out of reach for so many households in Seattle.

The collaboration between Allied8 & Frolic Community was critical to Corvidae Co-op’s existence.

Allied8 unlocked the additional density and affordability in traditionally single-family neighborhoods while Frolic’s model of co-operative ownership and cohousing unlocked the ability for individual owners to get mortgages on these suites in a cohesive legal, financial, and social structure that further drove down affordability. Other project partners included Habitat for Humanity, Seattle Office of Housing, Green Canopy NODE, 1st Security Bank, Rainier Valley Community Development Fund, Local Enterprise Assistance Fund.

Leah Martin is the co-founder of Allied8, an architecture, development and advocacy firm based in Seattle.

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