Snohomish County, WA Short-Term Rentals: Occupancy Limits (2026)

Snohomish County does not regulate short-term rentals as a stand-alone use in its Unified Development Code (Title 30 SCC), so unincorporated STRs default to the underlying single-family or duplex dwelling standards. Overnight occupancy in any dwelling is capped by the Washington State Residential Code (WAC 51-51, adopting the IRC) under the State Building Code Act (Chapter 19.27 RCW). IRC R304 requires every habitable room to have at least 70 square feet of floor area, and R304.2 requires 50 additional square feet per occupant when a room is shared by more than one person. Bedrooms must also have an emergency egress window meeting IRC R310 (minimum 5.7 sq ft net opening, 24 inch height, 20 inch width, sill no higher than 44 inches). Bed and breakfast inns and bed and breakfast guesthouses are separately regulated under SCC 30.28.020, which requires a certificate of occupancy from the department prior to allowing guests and an annual inspection and renewal; the use is allowed in many residential and rural zones (R-9,600 through A-10) by administrative conditional use permit. The Washington Short-Term Rental Operations Act, RCW 64.37, requires statewide DOR registration and $1 million liability coverage (or platform-provided coverage) regardless of local occupancy rules and does not preempt local building code occupancy limits. On-site septic systems regulated under WAC 246-272A also cap design occupancy by bedroom count, and exceeding the design flow can trigger a Snohomish Health Department violation.