Amid mounting housing affordability challenges, Washington state is taking bold steps to encourage faster and cheaper construction of accessory dwelling units (ADUs). A new law, recently signed by Governor Bob Ferguson, aims to expedite the building process of these small residential units by allowing registered architects to self-certify their designs for compliance with state building codes.

Substitute House Bill 1353, spearheaded by Rep. Alex Ramel of Bellingham, introduces a self-certification pathway specifically for detached ADUs — separate living units on the same lot as a single-family home. By reducing the permitting burden on local jurisdictions, lawmakers hope this measure will accelerate ADU construction and help ease the state’s housing crunch.

“This idea is already working in other states to cut permitting times and bring down costs,” said Ramel in a statement from the House Democrats. “It empowers architects to take responsibility for compliance while preserving safeguards through audits and inspections.”

A Response to a Growing Crisis

ADUs, sometimes referred to as backyard cottages or granny flats, have gained popularity across the country as a lower-cost, lower-footprint housing solution that integrates into existing neighborhoods. In urban centers like Seattle, Tacoma, and Spokane — where housing demand continues to outpace supply — the new law is being seen as a practical move to address the crisis without requiring massive redevelopment.

The program is voluntary for cities and counties governed by the state’s Growth Management Act (GMA). Local governments that opt in will still maintain oversight by auditing at least 20% of self-certified applications annually. This ensures that, while the process is expedited, quality and code compliance remain intact.

Cutting Through the Red Tape

Permitting delays have long been a barrier to ADU construction. According to stakeholders, some homeowners face wait times of six months or more just to get approval for standard designs. The self-certification program aims to change that by shifting some responsibility to qualified professionals, allowing jurisdictions to focus on more complex projects or enforcement.

“This is about unlocking housing options faster, but without abandoning accountability,” said a spokesperson from the state Department of Commerce, which is tasked with supporting cities that choose to adopt the new framework.

Looking Ahead

The law will go into effect 90 days after the end of the legislative session, and state agencies are preparing guidance documents for municipalities considering implementation. Officials hope to see results quickly, especially in cities where the housing shortage is most acute.

Homeowners interested in building detached ADUs are encouraged to consult with architects familiar with the program, as the changes could significantly reduce both the time and expense involved in adding a unit to their property.

With its passage, Substitute House Bill 1353 positions Washington as a leader in creative housing solutions, and advocates are hopeful that its success will inspire further innovations across the country.

Originally reported by Aaron Washington in Hoodline.