In parts of Washington, backyard cottages and in-law suites are on the rise

The growing popularity of “accessory dwelling units” in places that loosened rules for the homes offers clues for what could happen as a statewide ADU law takes effect.

By: - November 6, 2023 3:14 pm

An accessory dwelling unit built above Charles LaBrie’s garage in Spokane. (Courtesy of Charles LaBrie)

After Laura Craig’s father unexpectedly died in 2020, she and her family began looking at new housing options for her mother. 

Craig, who lives in Snohomish County, wanted to build an apartment above her family’s garage, but the county at the time did not allow for “accessory dwelling units” of that kind. The regulations were surprising to Craig, who owns one acre of property. 

“It just didn’t seem right or logical that I couldn’t build an ADU on top of my already existing garage,” she said. 

Last year, the county updated its guidance and now, three years later, the one-bedroom, 900-square foot apartment atop Craig’s garage is months away from being finished.

Similar restrictions on ADUs will soon lift across the state. The Legislature this year passed a bill that requires many cities and counties to allow at least two accessory dwelling units per lot.

It will take time before this state law is in full effect. But construction trends in localities that have already loosened ADU rules show signs of demand for these little homes. And advocates hope that building more of them will help to bridge the state’s shortfall in affordable housing while also offering an option for homeowners to earn income from their property.

“They create housing options for people in expensive single family neighborhoods who otherwise couldn’t afford to live there,” said Dan Bertolet, director of housing and urbanism with the Sightline Institute, a Seattle-based think tank.

‘One of the best ADU policies in the country’

An ADU is defined in the state law as a structure that provides independent sleeping, kitchen and bathroom facilities but is located on the same lot as another home. The law covers both attached units, such as basement or above-garage apartments, and backyard cottages and other detached accessory dwelling units, also known as “DADUs.”

A design for an accessory dwelling unit attached to a garage that that designer Charles LaBrie created for a client in Spokane. (Courtesy of LaBrie)

It applies to parts of the state that are subject to heightened planning requirements under a state law known as the Growth Management Act. This includes many of the state’s fastest-growing and most densely populated areas.

Though the law went into effect this summer, local governments don’t have to implement it until six months after their latest comprehensive plan updates, which occur on different timelines. Under the Growth Management Act, only a handful of counties complete their planning cycles each year, with the furthest out deadlines on the schedule now in 2027.

The state law was modeled in part on ADU legislation in Seattle.

Bertolet called the state’s new policy “one of the best ADU policies in the country.”

What the data shows 

Although Seattle is not representative of most cities in Washington, its growth with the construction of ADUs is an indication many people are interested in them, Bertolet said. 

After Seattle relaxed its ADU laws in 2019, the number of building permits for the structures spiked. In 2019, the city approved 283 attached and detached units. In 2021, it greenlighted 768, followed by 959 units in 2022.

Spokane last year loosened some of its restrictions on ADUs. It removed requirements that owners live in the main house on the property where the extra units are built and ended parking requirements. The city also expanded the allowable size of ADUs.

Spokane, too, saw a rise in ADU construction after the city adopted the changes. In 2018, Spokane approved only 21 ADU permits, for both attached and detached units. That number jumped to 40 in 2021 and to 51 in 2022.

“I think it will continue to grow,” said Tami Palmquist, the city’s development services director. “It’s one option that’s a little bit more affordable.” 

Snohomish County saw permits nearly double since it eased ADU restrictions last year. In 2022, the city permitted 91 units compared to 41 in 2021. So far this year, 104 have been permitted throughout the county. 

Washington’s statewide policy is similar to one in California. The Golden State has expanded where and how ADUs can be built with a number of laws since 2019. According to Sightline, roughly one in seven new homes permitted in California were ADUs, as of last year. 

“If things go the way they did in California, Washington could expect a big jump in production,” Bertolet said.

Who’s building them? 

Bertolet explained that ADUs are often seen as an “unobtrusive” way to increase housing availability. 

Some homeowners, like Craig, build ADUs to house family members. Craig said her in-laws are building a similar structure for her husband’s parents. 

For Charles LaBrie and his wife, building a one bedroom apartment above their garage gave them the opportunity to live on their Spokane property while they were finishing construction on their main house. 

LaBrie, who owns a construction and design company, has also helped draft plans for two ADUs for clients in Spokane. He spent almost a year building his $70,000 structure, which he and his wife completed mostly on their own. When their house is done, they will likely rent out the ADU, providing them a bit of extra cash, he said.

ADUs aren’t a viable option for all homeowners.

Kenmore resident Chris Brown was planning to build an ADU on her property, which she’s had for more than 30 years. Brown, who is in her mid-60s, said she was hoping to build a smaller space that she could live in while renting her main house as another source of income. 

But she ran into difficulties financing the project. Building a 1,400 square-foot detached structure would have cost around $532,000, she said. 

“Unless you have an income that is high enough to pay for the existing mortgage and the cost of building an ADU, you can’t do it,” she said. “It’s not really affordable for most people.”

Still, housing experts say ADUs are an important piece in solving the state’s affordable housing puzzle.

Washington needs more housing of all kinds to meet the growing need, Bertolet said. While “they’re not going to solve the whole issue” he added, “ADUs are one flavor.”

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Laurel Demkovich
Laurel Demkovich

Laurel joined States Newsroom in 2023 after almost three years as a statehouse reporter for the Spokesman-Review. She covers state government, the Legislature and all other Olympia news.

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