Quick answer · Issaquah ADU laws, 2026
In Issaquah, 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.
Issaquah implements HB 1337's two-ADU-per-lot right with no owner-occupancy requirement and DADUs up to 1,000 sq ft. Hillside parcels frequently need a geotechnical report as part of the building permit — worth confirming during feasibility rather than after design.
Issaquah pairs I-90 corridor job growth with some of the most varied lot terrain on the Eastside — valley-floor lots near Olde Town and hillside parcels toward the Highlands and Squak Mountain. ADUs here are popular for both rental income and multi-generational living.
Permit Office
Issaquah Permit Center
Puget Sound ADU Rent (market range)
$1,600–$2,800/mo
NW ADU Builders — serving Issaquah, WA
NW ADU Builders