Seattle considers ban for ‘McMansions,’ new rules for backyard cottages

The Seattle City Council is moving forward with discussions about wide-ranging proposals that could change the landscape of the city’s neighborhoods. The result could be new rules for backyard cottages and “McMansions.”

Councilman Mike O’Brien has been spearheading the legislation since 2016, aiming to ease existing restrictions on mother-in-law apartments and backyard cottages, also known as accessory dwelling units. The proposal also would crack down on so-called “McMansions,” by limiting the square footage of new homes relative to the size of a lot.

O’Brien argued the changes would boost the supply of affordable housing options and reduce the number of older homes being demolished.

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Under his proposal, the city would establish a maximum floor area ratio that limits new home construction. The proposal caps a home’s square footage by half compared to the size of the lot. For instance, a 5,000 square foot property could have no more than 2,500 square feet of living space above-ground.

As for cottages and mother-in-law suites, O’Brien’s plan calls for increasing the existing size of ADUs from 800 to 1,000 square feet and allow them to be built on smaller lots. It would allow both backyard cottages and mother-in-law units on the same property, but no longer require owners to live on-site. The plan increases the number of unrelated people who could live in an ADU to 12, up from eight.

The proposal also strips away the requirement for off-street parking spaces, something critics worry will make parking even more difficult in already-crowded neighborhoods.

“Where the parking is the biggest problem today are some of our denser, close-in neighborhoods that are really well-served by transit,” O’Brien said. “Adding a few more backyard cottages might bring a few more cars and it’s going to be a little bit harder, but those are neighborhoods where you don’t need a car to get around.”

Seattle backyard cottages and ADUs

A city analysis found that easing the rules would add twice as many ADUs over the next decade, up to 4,400 from less than 2,000. It also found the number of older homes being razed to make way for bigger homes would decline by 22 percent.

“We need thousands and thousands of additional units, and backyard cottages and in-laws are even in the best scenario going to be a relatively small piece of that,” O’Brien said. “But, we’re going to need lots of small pieces to come together to solve this crisis.

The proposed changes to ADUs have faced push back since 2016, when the Queen Anne Community Council launched a legal challenge, requiring the city to conduct an environmental impact statement. Earlier this month, a deputy hearing examiner found the EIS was adequate, clearing the way for O’Brien’s proposal to move forward.

QACC, however, questioned the ruling, arguing the city based its analysis on computer models and did not reach out to neighborhood groups.

“When you say no ownership requirement … with no parking requirements and allow 12 people to live on that site, then you have significant environmental impacts that are concerns of thousands of people in this city,” said Henry Martin Kaplan, QACC’s land-use chair.

Other critics have argued removing the owner-occupancy requirement could lead to the displacement of populations because developers could raze older houses and replace them with expensive rental units.

The council’s Wednesday hearing is the first in a series of meetings to discuss the new rules. A public hearing on the proposed legislation will be held June 11. The full council could vote on the proposed legislation June 18.

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