State building council debates smaller efficiency dwelling units, asks for design criteria and homework

The Washington State Building Code Council met Oct. 16, 2025, and discussed a proposal directing the council to recommend amendments that would permit minimum dwelling units smaller than the current efficiency dwelling unit size of 190 square feet.

Council members opened the discussion by reviewing model-code language and a Seattle director’s rule that allows smaller efficiency units. Dustin (staff member) said the group should use model code language as a starting point and noted Seattle’s director’s rule as an example. Micah, technical code development director for the Seattle Department of Construction and Inspections, said the National Healthy Housing Standard does not set a dwelling-unit size but does set a 70-square-foot minimum for habitable rooms, and that the Seattle rule aligns habitable-space minimums with that standard.

The conversation centered on three questions: what the council is trying to achieve (livability, health and sanitation, and expanded affordable housing options); whether to set a numeric lower bound or a performance-based standard; and what elements must be present for a space to qualify as a dwelling unit. Jay, the building official for Seattle’s Department of Construction and Inspections, described Seattle’s approach for compact dwelling units (CDUs): a 120-square-foot habitable space plus an additional occupiable area (for example, 30 square feet) and specific requirements for cooking and natural light. Jay said Seattle permits efficient cooking facilities (including allowances for microwave or other small cooking appliances) under its director’s rule and has been working to align multiplex/residential and building-code dwelling-unit sizing.

Members repeatedly returned to livability concerns beyond raw square footage: natural light and ventilation, storage, bathroom configuration (wet-bath versus full tub), accessibility and egress, and whether a unit would begin to resemble a sleeping room or congregate housing if it got too small. Bridal (staff member) and Micah emphasized that Seattle’s CDU rule includes requirements other than floor area—storage and natural light among them—and warned that smaller unit allowances often carry compensating requirements elsewhere in the code.

Several members said they do not favor leaving lower bounds entirely to the market. Brett and others argued for a state minimum set by the council, with the possibility of revising it through the established amendment process if needed. Josh (structural engineer) suggested a hybrid approach that combines total square-foot limits with required percentages or minimums for specific program elements (sleeping, cooking, bathing) to allow some design flexibility while preserving minimum livability.

By the end of the discussion the council agreed on homework and next steps. Dustin (staff member) said the tag will meet weekly on Thursdays from 1 to 2 p.m. through December and posted the immediate assignments: (1) review and post Seattle’s CDU director’s rule and related exhibits on the council’s dwelling-unit-size working page; (2) define the performance criteria the council wants the code to require (for example, ‘‘permanent provisions for cooking, living, eating and sleeping’’); and (3) consider whether to adopt a numeric lower bound, a performance-based standard, or a combination backed by design diagrams or a defensible statistical approach.

The meeting also handled procedural business after quorum was confirmed: the council voted to approve the meeting agenda and to approve minutes for Sept. 3 and Oct. 9.