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Puget Sound ADU & Backyard Cottage Builders
Licensed and actively building in King County, Pierce County, and Snohomish County — under Washington's 2026 ADU laws.
Quick answer · Puget Sound ADU laws, 2026
Every single-family lot in King, Pierce, and Snohomish counties can now host two ADUs under Washington's HB 1337 (2023) — with no owner-occupancy requirement, no off-street parking mandated on smaller lots or near major transit, and DADUs allowed up to 1,000 sq ft. As of June 11, 2026, HB 1345 also opens a path for one detached ADU on rural parcels outside urban growth areas if the county opts in.
ADUs can be sold as condominium units in Washington, design standards can't be stricter than for the main home, and cities can't require street improvements as a permit condition. See our full HB 1337 + HB 1345 breakdown.
King County
Every King County city inside an urban growth area now allows two ADUs per single-family lot under HB 1337. Seattle and Kirkland offer pre-approved DADU plan sets that can cut permit review to about 6 weeks; Bellevue, Redmond and Renton follow the same two-ADU right with no owner-occupancy requirement.
Pierce County
Tacoma, Puyallup and the rest of Pierce County's urban cities now allow two ADUs per lot under HB 1337 — up to 1,000 sq ft, no owner-occupancy required, no off-street parking mandated. Rural Pierce County parcels may qualify for one detached ADU under HB 1345 (effective June 11, 2026) if the county opts in.
Snohomish County
Everett, Lynnwood and the other Snohomish County cities enforce HB 1337's two-ADU-per-lot right with no owner-occupancy strings. With Lynnwood Link light rail online, off-street parking cannot be required for ADUs within a half mile of a station — which covers most of the Lynnwood and Mountlake Terrace cores.
Thurston County
Also serving Lacey, Olympia & Tumwater. Thurston cities follow Washington's HB 1337 two-ADU-per-lot rule with no owner-occupancy requirement.
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