Snohomish reworking its planning code to allow more ADUs to meet state law

SNOHOMISH — In the near future, city residents will be able to build more accessory dwelling units (ADUs) under rule changes the planning commission is currently working to reshape to meet state law.

ADUs are small living spaces with their own kitchen, bathroom and bedroom. ADUs can be built onto an existing house, or built as a second, smaller house on the property (called a detached ADU, “D-ADU”).

“It’s an affordable housing type that can bring passive income to homeowners,” city planning director Brooke Ediem told the planning commission last week, and it’s a type of housing that’s already in Snohomish.

State rule changes the Legislature set in 2023 to encourage more ADUs are making Snohomish modify its rulebook.

The state law requires cities of Snohomish’s size to allow up to two ADUs per residential lot. It must adjust its laws by a mid-2025 deadline.

Last week, members of the planning commission debated whether an ADU’s maximum size should be 1,000 square feet of floor space, or 1,100, or 1,200. Commissioner Gordon Cole, whose career is in constructing buildings, said 1,000 should be enough space to fit at least two bedrooms.

The state laws newly require ADUs be a minimum of 1,000 square feet. Snohomish’s minimum today is 800 square feet for a detached ADU.

For a size comparison, a single-wide mobile home can range from 500 to 1,300 square feet in floor plan, and the smallest doublewides start at around 1,000 square feet, according to the Manufactured Housing Institute. Tiny homes are rarely larger than 500 square feet, according to The Motley Fool. (Snohomish County’s own ADU codes for unincorporated restrict them to a maximum floor area of 1,200 square feet.)

ADUs could be two stories tall in Snohomish.

The city proposes that ADUs can be built up to 30 feet tall. The height limit next to alleys would be 24 feet tall, which can allow two stories, Eidem said.

The code also limits that ADUs can’t be placed in ways that impede vehicles maneuvering in alleyways.

The city cannot require the owner to live on the same property as an ADU, meaning the main house and the ADU could be rentals. One caveat revolves around short-stay rental platforms such as Airbnb or Vrbo; in those cases, the property owner must live on the property.

City Public Works wants all future Detached ADU buildings to have separate water and sewer hookups with meters. 

A few commissioners called this scenario unlikely, but said the hookup fees for utilities could stifle someone’s intent to add a detached ADU.

A public hearing on the ADU discussion will be at next month’s Snohomish Planning Commission meeting May 1 at 6 p.m.

City officials have a count of 39 ADUs already in town. Most are in the southern area, and some are in the eastside, Eidem said.

An estimated 2,250 properties in Snohomish are eligible to add an ADU or two. Realistically, the rule changes could see a trickle of more ADUs over time.

Any ADUs built in city-designated special zones such as the Pilchuck District (largely along Maple), Historic District (largely downtown) or Midtown District (mostly along Avenue D) would need to conform to the design standards of those districts.

When everything is all done, possibly by this fall, the city will create a whole city code section about ADUs. It would become Snohomish Municipal Code Chapter 14.170.