Zoning Changes Would Mean More Granny Flats and Fewer McMansions in Seattle

The Seattle City Council is considering a new ordinance that would ban the construction of large, detached single-family houses (more commonly referred to as McMansions) while also easing restrictions on accessory dwelling units (i.e., ADUs, but also commonly referred to as mother-in-law units of granny flats).

City Councilmember Mike O’Brien is championing the potentially game changing legislation, according to an article by Daniel Beekman. Mcmansions are a particularly popular building typology in Seattle these days, like in many other cities. "O’Brien’s proposed limit would have blocked almost half the new single-family houses constructed in Seattle since 2010, had it been on the books," according to Beekman.

As Beekman explains, the bill's dual purposes are the results of a political calculus intended to broker a partnership between two usually opposing forces: pro-development YIMBYs and anti-development homeowners (sometimes referred to as NIMBYs).

"O’Brien has described backyard cottages and basement apartments as a gentle way to add density as Seattle’s population grows, knowing he can count on urbanists as cheerleaders. By taking aim at McMansions, he hopes to also win support from residents grumpy about development."

According to Beekman, the proposal's less restrictive regulations of ADUs have gained more attention than the more restrictive regulations of McMansions.

As for the key matter of how the city's zoning code change would change to restrict the development of McMansions, Beekman provides the following explanation: "Under O’Brien’s legislation […] the city would adopt a maximum Floor Area Ratio (FAR) of 0.5 for new houses on most lots."

While the city considers these substantial changes to its zoning code and the types of single-family housing it will allow in the future, the Washington State Legislature recently approved legislation that would provide incentives for local governments to increase density.