Quick answer · Sammamish ADU laws, 2026
In Sammamish, King County, you can now build two ADUs on any single-family lot under Washington's HB 1337 (2023) — with no owner-occupancy requirement, no off-street parking mandate on smaller lots, and DADUs allowed up to 1,000 sq ft.
Sammamish follows HB 1337: two ADUs per single-family lot (attached, detached, or both), DADUs up to 1,000 sq ft, and no owner-occupancy requirement. Steep-slope and wetland buffers are common on the plateau and are reviewed as part of the same permit.
Sammamish plateau lots are among the largest in east King County, and demand from Microsoft and Eastside tech commuters keeps ADU interest high. Two-story DADUs are a common fit here — plenty of yard, but slopes and trees often shape the placement.
Permit Office
Sammamish Permit Center
Puget Sound ADU Rent (market range)
$1,600–$2,800/mo
NW ADU Builders — serving Sammamish, WA
NW ADU Builders