Legislation sponsored by Sen. Sharon Shewmake (D-Bellingham) to expand construction of accessory dwelling units, or ADUs, passed the Senate on a 42-6 vote today.

ADUs, often referred to as backyard cottages or mother-in-law units, are residential homes that occupy the same lot as an existing home. As smaller buildings that share a lot, they are typically more affordable and more environmentally friendly than a traditional single-family home.

Currently, many local regulations make ADUs expensive or difficult to build, limiting the supply of them available to renters and buyers. Shewmake’s bill, SB 5235, would cut red tape and remove some barriers to construction, and would require comprehensive plans under the Growth Management Act to allow for ADUs within an urban growth area.

“We need housing options as diverse as our communities are,” said Shewmake. “An ADU isn’t right for everyone, but it might be perfect for someone looking for an affordable place to live, or a homeowner with extra space on their lot to build. We should cut the red tape and make it easier to build these, not put up roadblocks and make it harder.”

Shewmake praised the work by the city of Ferndale to encourage construction of ADUs and hoped that passage of her legislation would nudge more local governments to similarly support ADUs.

“ADUs, and this bill, won’t solve Washington’s affordable housing crisis all on their own, but they’re important part of the mix,” said Shewmake. “ADUs allow regular people to build additional housing that is naturally affordable — units for seniors looking to downsize, young people starting out, smaller families and anyone else who can economize on space. This is a way to create more affordable housing and empower homeowners, and I love that.”

The bill now goes to the House for consideration.