Council considers adding IRC‑level sound‑transmission rules to multiplex appendix after public and TAG input

At a July 14 work session the State Building Code Council discussed a public comment from John Hsu that recommended adding sound‑transmission (STC/IIC) requirements from the IRC appendix for multiplex housing. Council members and stakeholders broadly supported investigating the change given health and habitability concerns for adjacent units.

Dustin (staff) opened the comment and showed the proposed language; John Hsu said he was “recommending the IRC level.” Roger and Angela said sound transmission is a health and well‑being issue and supported adding the provision to the multiplex appendix. Roger said the suggestion “actually makes a lot of sense” and that the TAG had not discussed sound transmission at length.

Members asked about cost. Dustin offered a rapid materials estimate: “About a dollar 50 per square foot for materials and 4 hours of labor per 320, square feet of wall.” Patrick Hanks (Building Industry Association of Washington) and other industry representatives confirmed there are a range of options—extra gypsum layers, resilient channels, or floor topping to meet STC/IIC—and that material-only impacts could be modest (staff and council gave rough estimates around $1.50–$2.00 per square foot for assembly materials, with labor and system choices varying by project).

Katie Sheehan, drawing on prior fair‑housing practice, said she saw many noise complaints in multiunit housing and supported requiring sound measures to reduce tenant harm.

Council members agreed the question is technical and asked staff to gather more detailed cost and design input (including from architects and the absent architecture seat) and to draft amendment language. Roger volunteered to coordinate comments and to lead a council amendment effort when members have suggested language; staff will post any proposed amendments and the amendment tracker for member review.

Next steps: staff will solicit more detailed technical cost/assembly information, incorporate member suggestions, and return proposed amendment text for council consideration at a subsequent meeting.