Senate passes ‘nation’s best’ reforms on mother-in-law units - referred to House

Mother-in-law cottage or
Accessory Dwelling Unit (ADU)

OLYMPIA – The Washington State Senate voted 38-10 Monday to smooth the way for homeowners to add mother-in-law suites, backyard cottages, and other accessory dwelling units (ADUs).

Senate Bill 5812, sponsored by Sen. Guy Palumbo (D-Maltby), requires certain cities and counties to adopt ordinances and zoning regulations to authorize accessory dwelling units.

“We have a housing and homelessness crisis and our constituents are demanding that we deal with the supply problem,” said Palumbo. 

“ADUs represent a happy medium since they can increase housing density within the framework of existing neighborhoods without changing the neighborhood character. This is low hanging fruit to ease the housing shortage.”

Called “the nation’s best ADU reform,” by the Sightline Institute, the bill requires cities with populations greater than 10,000, and cities with populations between 2,500 and 10,000 within transit service districts, to adopt ADU ordinances. The ordinances must allow ADUs on lots with single-family housing units and may not impose exorbitant impact fees or prohibitive regulations.

The bill exempts cities that have already instituted or are currently working on ADU ordinances. In addition, it allows for local tree retention policies and exempts historical districts.

The bill now goes to the state House of Representatives for consideration.