ADU permit requirements across King, Pierce & Snohomish counties
Side-by-side: which 82 cities and counties require a permit for a ADU, what triggers one, what it costs, and how long review takes. Verified against each jurisdiction's own page; sources cited per row.
81 of 82 jurisdictions have authoritative rules on file · 81 typically require a permit · 0 often do not.
King County
| Jurisdiction | Permit? | Threshold | Fee | Review days | Source |
|---|---|---|---|---|---|
City of Algona city | Yes | WA HB 1337 (effective 2024) requires cities ≥6,000 pop. to allow 2 ADUs per lot in residential zones, max 1,000 sq ft, no owner-occupancy requirement, no parking requirement near transit. Local size + design caps apply. | Full Construction Permit (Addition/Alteration) fees. Sewer capacity charges may apply (King County: ~$8k-$10k). Apply via https://www.cityofalgona.com/building-permits. Small city near Auburn. Apply in person at city hall or via mailed forms. | 30–120 days | Cite verified 2026-04-28 |
City of Auburn city | Yes | WA HB 1337 (effective 2024) requires cities ≥6,000 pop. to allow 2 ADUs per lot in residential zones, max 1,000 sq ft, no owner-occupancy requirement, no parking requirement near transit. Local size + design caps apply. | Full Construction Permit (Addition/Alteration) fees. Sewer capacity charges may apply (King County: ~$8k-$10k). Apply via https://mybuildingpermit.com. Apply via MyBuildingPermit.com. | 30–120 days | Cite verified 2026-04-26 |
City of Bellevue city | Yes | WA HB 1337 (effective 2024) requires cities ≥6,000 pop. to allow 2 ADUs per lot in residential zones, max 1,000 sq ft, no owner-occupancy requirement, no parking requirement near transit. Local size + design caps apply. | Full Construction Permit (Addition/Alteration) fees. Sewer capacity charges may apply (King County: ~$8k-$10k). Apply via https://mybuildingpermit.com. | 21–90 days | Cite verified 2026-04-26 |
City of Black Diamond city | Yes | WA HB 1337 (effective 2024) requires cities ≥6,000 pop. to allow 2 ADUs per lot in residential zones, max 1,000 sq ft, no owner-occupancy requirement, no parking requirement near transit. Local size + design caps apply. | Full Construction Permit (Addition/Alteration) fees. Sewer capacity charges may apply (King County: ~$8k-$10k). Apply via https://www.blackdiamondwa.gov/161/Permits. Black Diamond Community Development handles permits. | 30–120 days | Cite verified 2026-04-28 |
City of Burien city | Yes | WA HB 1337 (effective 2024) requires cities ≥6,000 pop. to allow 2 ADUs per lot in residential zones, max 1,000 sq ft, no owner-occupancy requirement, no parking requirement near transit. Local size + design caps apply. | Full Construction Permit (Addition/Alteration) fees. Sewer capacity charges may apply (King County: ~$8k-$10k). Apply via https://mybuildingpermit.com. Apply via MyBuildingPermit.com. | 30–120 days | Cite verified 2026-04-26 |
City of Carnation city | Yes | WA HB 1337 (effective 2024) requires cities ≥6,000 pop. to allow 2 ADUs per lot in residential zones, max 1,000 sq ft, no owner-occupancy requirement, no parking requirement near transit. Local size + design caps apply. | Full Construction Permit (Addition/Alteration) fees. Sewer capacity charges may apply (King County: ~$8k-$10k). Apply via https://carnationwa.gov/development-services/. Carnation Development Services handles permits. | 30–120 days | Cite verified 2026-04-28 |
City of Clyde Hill city | Yes | WA HB 1337 (effective 2024) requires cities ≥6,000 pop. to allow 2 ADUs per lot in residential zones, max 1,000 sq ft, no owner-occupancy requirement, no parking requirement near transit. Local size + design caps apply. | Full Construction Permit (Addition/Alteration) fees. Sewer capacity charges may apply (King County: ~$8k-$10k). Apply via https://www.clydehill.org/government/building-permits. Clyde Hill Building Department handles permits. | 30–120 days | Cite verified 2026-04-28 |
City of Covington city | Yes | WA HB 1337 (effective 2024) requires cities ≥6,000 pop. to allow 2 ADUs per lot in residential zones, max 1,000 sq ft, no owner-occupancy requirement, no parking requirement near transit. Local size + design caps apply. | Full Construction Permit (Addition/Alteration) fees. Sewer capacity charges may apply (King County: ~$8k-$10k). Apply via https://www.covingtonwa.gov/government/community_development/permits.php. Covington Community Development handles permits. | 30–120 days | Cite verified 2026-04-28 |
City of Des Moines city | Yes | WA HB 1337 (effective 2024) requires cities ≥6,000 pop. to allow 2 ADUs per lot in residential zones, max 1,000 sq ft, no owner-occupancy requirement, no parking requirement near transit. Local size + design caps apply. | Full Construction Permit (Addition/Alteration) fees. Sewer capacity charges may apply (King County: ~$8k-$10k). Apply via https://www.desmoineswa.gov/government/community_development/permits/index.php. Des Moines Community Development handles permits. | 30–120 days | Cite verified 2026-04-28 |
City of Duvall city | Yes | WA HB 1337 (effective 2024) requires cities ≥6,000 pop. to allow 2 ADUs per lot in residential zones, max 1,000 sq ft, no owner-occupancy requirement, no parking requirement near transit. Local size + design caps apply. | Full Construction Permit (Addition/Alteration) fees. Sewer capacity charges may apply (King County: ~$8k-$10k). Apply via https://www.duvallwa.gov/178/Permit-Center. Duvall Permit Center handles permits. | 30–120 days | Cite verified 2026-04-28 |
City of Enumclaw city | Yes | WA HB 1337 (effective 2024) requires cities ≥6,000 pop. to allow 2 ADUs per lot in residential zones, max 1,000 sq ft, no owner-occupancy requirement, no parking requirement near transit. Local size + design caps apply. | Full Construction Permit (Addition/Alteration) fees. Sewer capacity charges may apply (King County: ~$8k-$10k). Apply via https://www.cityofenumclaw.net/305/Building. Enumclaw Building Division handles permits. | 30–120 days | Cite verified 2026-04-28 |
City of Federal Way city | Yes | WA HB 1337 (effective 2024) requires cities ≥6,000 pop. to allow 2 ADUs per lot in residential zones, max 1,000 sq ft, no owner-occupancy requirement, no parking requirement near transit. Local size + design caps apply. | Full Construction Permit (Addition/Alteration) fees. Sewer capacity charges may apply (King County: ~$8k-$10k). Apply via https://mybuildingpermit.com. Apply via MyBuildingPermit.com. | 30–120 days | Cite verified 2026-04-26 |
City of Issaquah city | Yes | WA HB 1337 (effective 2024) requires cities ≥6,000 pop. to allow 2 ADUs per lot in residential zones, max 1,000 sq ft, no owner-occupancy requirement, no parking requirement near transit. Local size + design caps apply. | Full Construction Permit (Addition/Alteration) fees. Sewer capacity charges may apply (King County: ~$8k-$10k). Apply via https://mybuildingpermit.com. Apply via MyBuildingPermit.com. | 45–120 days | Cite verified 2026-04-26 |
City of Kenmore city | Yes | WA HB 1337 (effective 2024) requires cities ≥6,000 pop. to allow 2 ADUs per lot in residential zones, max 1,000 sq ft, no owner-occupancy requirement, no parking requirement near transit. Local size + design caps apply. | Full Construction Permit (Addition/Alteration) fees. Sewer capacity charges may apply (King County: ~$8k-$10k). Apply via https://mybuildingpermit.com. Apply via MyBuildingPermit.com. | 30–120 days | Cite verified 2026-04-28 |
City of Kent city | Yes | WA HB 1337 (effective 2024) requires cities ≥6,000 pop. to allow 2 ADUs per lot in residential zones, max 1,000 sq ft, no owner-occupancy requirement, no parking requirement near transit. Local size + design caps apply. | Full Construction Permit (Addition/Alteration) fees. Sewer capacity charges may apply (King County: ~$8k-$10k). Apply via https://kentwa.gov/permits. Kent uses MyKent permits portal. | 30–90 days | Cite verified 2026-04-26 |
City of Kirkland city | Yes | WA HB 1337 (effective 2024) requires cities ≥6,000 pop. to allow 2 ADUs per lot in residential zones, max 1,000 sq ft, no owner-occupancy requirement, no parking requirement near transit. Local size + design caps apply. | Full Construction Permit (Addition/Alteration) fees. Sewer capacity charges may apply (King County: ~$8k-$10k). Apply via https://mybuildingpermit.com. Apply via MyBuildingPermit.com. | 21–60 days | Cite verified 2026-04-26 |
City of Lake Forest Park city | Yes | WA HB 1337 (effective 2024) requires cities ≥6,000 pop. to allow 2 ADUs per lot in residential zones, max 1,000 sq ft, no owner-occupancy requirement, no parking requirement near transit. Local size + design caps apply. | Full Construction Permit (Addition/Alteration) fees. Sewer capacity charges may apply (King County: ~$8k-$10k). Apply via https://mybuildingpermit.com. Apply via MyBuildingPermit.com. | 30–120 days | Cite verified 2026-04-28 |
City of Maple Valley city | Yes | WA HB 1337 (effective 2024) requires cities ≥6,000 pop. to allow 2 ADUs per lot in residential zones, max 1,000 sq ft, no owner-occupancy requirement, no parking requirement near transit. Local size + design caps apply. | Full Construction Permit (Addition/Alteration) fees. Sewer capacity charges may apply (King County: ~$8k-$10k). Apply via https://maplevalleywa.gov/our-city/community-development/permits. Maple Valley Community Development handles permits. | 30–120 days | Cite verified 2026-04-28 |
City of Medina city | Yes | WA HB 1337 (effective 2024) requires cities ≥6,000 pop. to allow 2 ADUs per lot in residential zones, max 1,000 sq ft, no owner-occupancy requirement, no parking requirement near transit. Local size + design caps apply. | Full Construction Permit (Addition/Alteration) fees. Sewer capacity charges may apply (King County: ~$8k-$10k). Apply via https://www.medina-wa.gov/development-services/page/permits. Medina Development Services handles permits. | 30–120 days | Cite verified 2026-04-28 |
City of Mercer Island city | Yes | WA HB 1337 (effective 2024) requires cities ≥6,000 pop. to allow 2 ADUs per lot in residential zones, max 1,000 sq ft, no owner-occupancy requirement, no parking requirement near transit. Local size + design caps apply. | Full Construction Permit (Addition/Alteration) fees. Sewer capacity charges may apply (King County: ~$8k-$10k). | 30–120 days | Cite verified 2026-04-29 |
City of Milton (King) city | Yes | WA HB 1337 (effective 2024) requires cities ≥6,000 pop. to allow 2 ADUs per lot in residential zones, max 1,000 sq ft, no owner-occupancy requirement, no parking requirement near transit. Local size + design caps apply. | Full Construction Permit (Addition/Alteration) fees. Sewer capacity charges may apply (King County: ~$8k-$10k). Apply via https://www.cityofmilton.net/community-development. City of Milton straddles King and Pierce counties; Community Development handles permits for both. | 30–120 days | Cite verified 2026-04-28 |
City of Newcastle city | Yes | WA HB 1337 (effective 2024) requires cities ≥6,000 pop. to allow 2 ADUs per lot in residential zones, max 1,000 sq ft, no owner-occupancy requirement, no parking requirement near transit. Local size + design caps apply. | Full Construction Permit (Addition/Alteration) fees. Sewer capacity charges may apply (King County: ~$8k-$10k). Apply via https://mybuildingpermit.com. Apply via MyBuildingPermit.com. | 30–120 days | Cite verified 2026-04-28 |
City of Normandy Park city | Yes | WA HB 1337 (effective 2024) requires cities ≥6,000 pop. to allow 2 ADUs per lot in residential zones, max 1,000 sq ft, no owner-occupancy requirement, no parking requirement near transit. Local size + design caps apply. | Full Construction Permit (Addition/Alteration) fees. Sewer capacity charges may apply (King County: ~$8k-$10k). Apply via https://www.normandyparkwa.gov/community-development/page/permitsapplications. Normandy Park Community Development handles permits. | 30–120 days | Cite verified 2026-04-28 |
City of North Bend city | Yes | WA HB 1337 (effective 2024) requires cities ≥6,000 pop. to allow 2 ADUs per lot in residential zones, max 1,000 sq ft, no owner-occupancy requirement, no parking requirement near transit. Local size + design caps apply. | Full Construction Permit (Addition/Alteration) fees. Sewer capacity charges may apply (King County: ~$8k-$10k). Apply via https://northbendwa.gov/164/Permits. North Bend Community & Economic Development handles permits. | 30–120 days | Cite verified 2026-04-28 |
City of Pacific city | Yes | WA HB 1337 (effective 2024) requires cities ≥6,000 pop. to allow 2 ADUs per lot in residential zones, max 1,000 sq ft, no owner-occupancy requirement, no parking requirement near transit. Local size + design caps apply. | Full Construction Permit (Addition/Alteration) fees. Sewer capacity charges may apply (King County: ~$8k-$10k). Apply via https://www.pacificwa.gov/cms/One.aspx?portalId=176432&pageId=235953. Pacific straddles King and Pierce counties. Community Development handles permits for both. | 30–120 days | Cite verified 2026-04-28 |
City of Redmond city | Yes | WA HB 1337 (effective 2024) requires cities ≥6,000 pop. to allow 2 ADUs per lot in residential zones, max 1,000 sq ft, no owner-occupancy requirement, no parking requirement near transit. Local size + design caps apply. | Full Construction Permit (Addition/Alteration) fees. Sewer capacity charges may apply (King County: ~$8k-$10k). Apply via https://eplans.redmond.gov. Redmond uses ePlans portal. | 21–60 days | Cite verified 2026-04-26 |
City of Renton city | Yes | WA HB 1337 (effective 2024) requires cities ≥6,000 pop. to allow 2 ADUs per lot in residential zones, max 1,000 sq ft, no owner-occupancy requirement, no parking requirement near transit. Local size + design caps apply. | Full Construction Permit (Addition/Alteration) fees. Sewer capacity charges may apply (King County: ~$8k-$10k). Apply via https://permits.rentonwa.gov. Renton uses TRAKiT permits portal. | 30–90 days | Cite verified 2026-04-26 |
City of Sammamish city | Yes | WA HB 1337 (effective 2024) requires cities ≥6,000 pop. to allow 2 ADUs per lot in residential zones, max 1,000 sq ft, no owner-occupancy requirement, no parking requirement near transit. Local size + design caps apply. | Full Construction Permit (Addition/Alteration) fees. Sewer capacity charges may apply (King County: ~$8k-$10k). Apply via https://mybuildingpermit.com. Apply via MyBuildingPermit.com. | 45–120 days | Cite verified 2026-04-26 |
City of SeaTac city | Yes | WA HB 1337 (effective 2024) requires cities ≥6,000 pop. to allow 2 ADUs per lot in residential zones, max 1,000 sq ft, no owner-occupancy requirement, no parking requirement near transit. Local size + design caps apply. | Full Construction Permit (Addition/Alteration) fees. Sewer capacity charges may apply (King County: ~$8k-$10k). Apply via https://www.seatacwa.gov/our-city/departments/community-and-economic-development/permits-licenses. SeaTac Community & Economic Development handles permits. | 30–120 days | Cite verified 2026-04-28 |
City of Seattle city | Yes | Max 2 ADUs per property (Seattle code). Pre-approved DADU plans via ADUniverse cut review to 2-6 weeks. Custom designs follow standard plan submittal (SDCI Tips 103 + 106). Owner-occupancy covenant currently required. | Construction Permit (Addition/Alteration). Pay 75% of plan-review + permit fees at application acceptance. See 2026 Fee Estimator + Director's Rule 5-2025. Pre-approved DADU plans waive most plan-review fees. | 14–84 days | Cite verified 2026-04-26 |
City of Shoreline city | Yes | WA HB 1337 (effective 2024) requires cities ≥6,000 pop. to allow 2 ADUs per lot in residential zones, max 1,000 sq ft, no owner-occupancy requirement, no parking requirement near transit. Local size + design caps apply. | Full Construction Permit (Addition/Alteration) fees. Sewer capacity charges may apply (King County: ~$8k-$10k). Apply via https://www.shorelinewa.gov/government/departments/planning-community-development. Shoreline uses its own permit center. | 30–90 days | Cite verified 2026-04-26 |
City of Snoqualmie city | Yes | WA HB 1337 (effective 2024) requires cities ≥6,000 pop. to allow 2 ADUs per lot in residential zones, max 1,000 sq ft, no owner-occupancy requirement, no parking requirement near transit. Local size + design caps apply. | Full Construction Permit (Addition/Alteration) fees. Sewer capacity charges may apply (King County: ~$8k-$10k). Apply via https://www.snoqualmiewa.gov/206/Permit-Center. Snoqualmie Permit Center handles permits. | 30–120 days | Cite verified 2026-04-28 |
City of Tukwila city | Yes | WA HB 1337 (effective 2024) requires cities ≥6,000 pop. to allow 2 ADUs per lot in residential zones, max 1,000 sq ft, no owner-occupancy requirement, no parking requirement near transit. Local size + design caps apply. | Full Construction Permit (Addition/Alteration) fees. Sewer capacity charges may apply (King County: ~$8k-$10k). Apply via https://mybuildingpermit.com. Apply via MyBuildingPermit.com. | 30–120 days | Cite verified 2026-04-28 |
City of Woodinville city | Yes | WA HB 1337 (effective 2024) requires cities ≥6,000 pop. to allow 2 ADUs per lot in residential zones, max 1,000 sq ft, no owner-occupancy requirement, no parking requirement near transit. Local size + design caps apply. | Full Construction Permit (Addition/Alteration) fees. Sewer capacity charges may apply (King County: ~$8k-$10k). Apply via https://www.ci.woodinville.wa.us/government/development-services/permits. Woodinville Development Services handles permits. | 30–120 days | Cite verified 2026-04-28 |
King County (unincorporated) county | Yes | One ADU per primary dwelling. Owner-occupancy required (either ADU or primary). ADU max size: 1,000 sqft heated + 1,000 sqft unheated, except when wholly contained in basement/attic (or detached ADU basement floor area does not count). No additional off-street parking required. Detached ADU minimum lot sizes by zone: UR/R = 5,000 sqft; RA-2.5 = 1.875 ac; RA-5 = 3.75 ac (or 2.5 ac with TDR purchase); RA-10 = 7.5 ac; RA-20 = 15 ac; A-10 = 10 ac; A-35 = 35 ac. If lot smaller than minimums OR more than one primary dwelling, ADU must be attached or wholly contained in basement/attic. | Full Construction Permit (Addition/Alteration) fees. Sewer capacity charges may apply (King County: ~$8k-$10k). | 30–120 days | Cite verified 2026-04-29 |
Town of Beaux Arts Village city | Yes | WA HB 1337 (effective 2024) requires cities ≥6,000 pop. to allow 2 ADUs per lot in residential zones, max 1,000 sq ft, no owner-occupancy requirement, no parking requirement near transit. Local size + design caps apply. | Full Construction Permit (Addition/Alteration) fees. Sewer capacity charges may apply (King County: ~$8k-$10k). Apply via https://kingcounty.gov/en/dept/local-services/buildings-property/permits. Small village (~300 residents) on Lake Washington. Building permits processed via King County DLS by interlocal agreement. | 30–120 days | Cite verified 2026-04-28 |
Town of Hunts Point city | Yes | WA HB 1337 (effective 2024) requires cities ≥6,000 pop. to allow 2 ADUs per lot in residential zones, max 1,000 sq ft, no owner-occupancy requirement, no parking requirement near transit. Local size + design caps apply. | Full Construction Permit (Addition/Alteration) fees. Sewer capacity charges may apply (King County: ~$8k-$10k). Apply via https://kingcounty.gov/en/dept/local-services/buildings-property/permits. Town of ~500 contracts with King County DLS for permit processing. | 30–120 days | Cite verified 2026-04-28 |
Town of Skykomish city | Yes | WA HB 1337 (effective 2024) requires cities ≥6,000 pop. to allow 2 ADUs per lot in residential zones, max 1,000 sq ft, no owner-occupancy requirement, no parking requirement near transit. Local size + design caps apply. | Full Construction Permit (Addition/Alteration) fees. Sewer capacity charges may apply (King County: ~$8k-$10k). Apply via https://kingcounty.gov/en/dept/local-services/buildings-property/permits. Small mountain town (~200 residents). Most permitting via King County DLS. | 30–120 days | Cite verified 2026-04-28 |
Town of Yarrow Point city | Yes | WA HB 1337 (effective 2024) requires cities ≥6,000 pop. to allow 2 ADUs per lot in residential zones, max 1,000 sq ft, no owner-occupancy requirement, no parking requirement near transit. Local size + design caps apply. | Full Construction Permit (Addition/Alteration) fees. Sewer capacity charges may apply (King County: ~$8k-$10k). Apply via https://kingcounty.gov/en/dept/local-services/buildings-property/permits. Town contracts with King County DLS for permit processing. | 30–120 days | Cite verified 2026-04-28 |
Washington State (baseline) county | Yes | WA HB 1337 (effective 2024) requires cities ≥6,000 pop. to allow 2 ADUs per lot in residential zones, max 1,000 sq ft, no owner-occupancy requirement, no parking requirement near transit. Local size + design caps apply. | Full Construction Permit (Addition/Alteration) fees. Sewer capacity charges may apply (King County: ~$8k-$10k). | 30–120 days | Cite verified 2026-04-26 |
Pierce County
| Jurisdiction | Permit? | Threshold | Fee | Review days | Source |
|---|---|---|---|---|---|
City of Bonney Lake city | Yes | WA HB 1337 (effective 2024) requires cities ≥6,000 pop. to allow 2 ADUs per lot in residential zones, max 1,000 sq ft, no owner-occupancy requirement, no parking requirement near transit. Local size + design caps apply. | Full Construction Permit (Addition/Alteration) fees. Sewer capacity charges may apply (King County: ~$8k-$10k). Apply via https://www.cityofbonneylake.org. Bonney Lake runs its own permit center. | 30–120 days | Cite verified 2026-04-29 |
City of Buckley city | Yes | WA HB 1337 (effective 2024) requires cities ≥6,000 pop. to allow 2 ADUs per lot in residential zones, max 1,000 sq ft, no owner-occupancy requirement, no parking requirement near transit. Local size + design caps apply. | Full Construction Permit (Addition/Alteration) fees. Sewer capacity charges may apply (King County: ~$8k-$10k). Apply via https://www.piercecountywa.gov/PALS. Permits via Pierce County PALS. | 30–120 days | Cite verified 2026-04-29 |
City of DuPont city | Yes | WA HB 1337 (effective 2024) requires cities ≥6,000 pop. to allow 2 ADUs per lot in residential zones, max 1,000 sq ft, no owner-occupancy requirement, no parking requirement near transit. Local size + design caps apply. | Full Construction Permit (Addition/Alteration) fees. Sewer capacity charges may apply (King County: ~$8k-$10k). Apply via https://www.dupontwa.gov. DuPont runs its own permit center. | 30–120 days | Cite verified 2026-04-29 |
City of Edgewood city | Yes | WA HB 1337 (effective 2024) requires cities ≥6,000 pop. to allow 2 ADUs per lot in residential zones, max 1,000 sq ft, no owner-occupancy requirement, no parking requirement near transit. Local size + design caps apply. | Full Construction Permit (Addition/Alteration) fees. Sewer capacity charges may apply (King County: ~$8k-$10k). Apply via https://cityofedgewood.org. Edgewood Community Development. | 30–120 days | Cite verified 2026-04-29 |
City of Fife city | Yes | WA HB 1337 (effective 2024) requires cities ≥6,000 pop. to allow 2 ADUs per lot in residential zones, max 1,000 sq ft, no owner-occupancy requirement, no parking requirement near transit. Local size + design caps apply. | Full Construction Permit (Addition/Alteration) fees. Sewer capacity charges may apply (King County: ~$8k-$10k). Apply via https://cityoffife.org. Fife runs its own permit center. | 30–120 days | Cite verified 2026-04-29 |
City of Fircrest city | Yes | WA HB 1337 (effective 2024) requires cities ≥6,000 pop. to allow 2 ADUs per lot in residential zones, max 1,000 sq ft, no owner-occupancy requirement, no parking requirement near transit. Local size + design caps apply. | Full Construction Permit (Addition/Alteration) fees. Sewer capacity charges may apply (King County: ~$8k-$10k). Apply via https://www.cityoffircrest.net. Fircrest runs its own permit center. | 30–120 days | Cite verified 2026-04-29 |
City of Gig Harbor city | Yes | WA HB 1337 (effective 2024) requires cities ≥6,000 pop. to allow 2 ADUs per lot in residential zones, max 1,000 sq ft, no owner-occupancy requirement, no parking requirement near transit. Local size + design caps apply. | Full Construction Permit (Addition/Alteration) fees. Sewer capacity charges may apply (King County: ~$8k-$10k). Apply via https://www.cityofgigharbor.net. Gig Harbor permit center. | 30–120 days | Cite verified 2026-04-26 |
City of Lakewood city | Yes | WA HB 1337 (effective 2024) requires cities ≥6,000 pop. to allow 2 ADUs per lot in residential zones, max 1,000 sq ft, no owner-occupancy requirement, no parking requirement near transit. Local size + design caps apply. | Full Construction Permit (Addition/Alteration) fees. Sewer capacity charges may apply (King County: ~$8k-$10k). | 30–120 days | Cite verified 2026-04-29 |
City of Milton (Pierce) city | Yes | WA HB 1337 (effective 2024) requires cities ≥6,000 pop. to allow 2 ADUs per lot in residential zones, max 1,000 sq ft, no owner-occupancy requirement, no parking requirement near transit. Local size + design caps apply. | Full Construction Permit (Addition/Alteration) fees. Sewer capacity charges may apply (King County: ~$8k-$10k). Apply via https://cityofmilton.net. Milton (Pierce side) runs its own permit center. | 30–120 days | Cite verified 2026-04-29 |
City of Orting city | Yes | WA HB 1337 (effective 2024) requires cities ≥6,000 pop. to allow 2 ADUs per lot in residential zones, max 1,000 sq ft, no owner-occupancy requirement, no parking requirement near transit. Local size + design caps apply. | Full Construction Permit (Addition/Alteration) fees. Sewer capacity charges may apply (King County: ~$8k-$10k). Apply via https://www.piercecountywa.gov/PALS. Permits via Pierce County PALS. | 30–120 days | Cite verified 2026-04-29 |
City of Puyallup city | Yes | Permit required for any new detached accessory building >200sqft. Sheds/outbuildings ≤200sqft do not require a permit. | Full Construction Permit (Addition/Alteration) fees. Sewer capacity charges may apply (King County: ~$8k-$10k). | 30–120 days | Cite verified 2026-04-29 |
City of Roy city | Yes | WA HB 1337 (effective 2024) requires cities ≥6,000 pop. to allow 2 ADUs per lot in residential zones, max 1,000 sq ft, no owner-occupancy requirement, no parking requirement near transit. Local size + design caps apply. | Full Construction Permit (Addition/Alteration) fees. Sewer capacity charges may apply (King County: ~$8k-$10k). Apply via https://www.piercecountywa.gov/PALS. Town (~820 residents) — permits via Pierce County PALS. | 30–120 days | Cite verified 2026-04-29 |
City of Sumner city | Yes | WA HB 1337 (effective 2024) requires cities ≥6,000 pop. to allow 2 ADUs per lot in residential zones, max 1,000 sq ft, no owner-occupancy requirement, no parking requirement near transit. Local size + design caps apply. | Full Construction Permit (Addition/Alteration) fees. Sewer capacity charges may apply (King County: ~$8k-$10k). Apply via https://www.sumnerwa.gov. Sumner permit center. | 30–120 days | Cite verified 2026-04-26 |
City of Tacoma city | Yes | Two ADUs per lot allowed (any lot size/width in residentially-zoned districts). Living area limited to 1,000 sqft (excluding non-living areas). Detached ADU setbacks: 5ft side property line (8ft if main entrance faces side), 15ft rear property line (no setback from alleys). Subject to standard zone height limits. | Apply via https://aca-prod.accela.com/tacoma/Default.aspx (Accela ACA portal) or in person at 747 Market Street, 3rd Floor. | 21–60 days | Cite verified 2026-04-29 |
City of University Place city | Yes | WA HB 1337 (effective 2024) requires cities ≥6,000 pop. to allow 2 ADUs per lot in residential zones, max 1,000 sq ft, no owner-occupancy requirement, no parking requirement near transit. Local size + design caps apply. | Full Construction Permit (Addition/Alteration) fees. Sewer capacity charges may apply (King County: ~$8k-$10k). Apply via https://www.cityofup.com. University Place P&DS. | 30–120 days | Cite verified 2026-04-26 |
Pierce County (unincorporated) county | Yes | WA HB 1337 (effective 2024) requires cities ≥6,000 pop. to allow 2 ADUs per lot in residential zones, max 1,000 sq ft, no owner-occupancy requirement, no parking requirement near transit. Local size + design caps apply. | Full Construction Permit (Addition/Alteration) fees. Sewer capacity charges may apply (King County: ~$8k-$10k). Apply via https://www.piercecountywa.gov/PALS. Pierce County PALS portal. | 30–90 days | Cite verified 2026-04-26 |
Town of Carbonado city | Yes | WA HB 1337 (effective 2024) requires cities ≥6,000 pop. to allow 2 ADUs per lot in residential zones, max 1,000 sq ft, no owner-occupancy requirement, no parking requirement near transit. Local size + design caps apply. | Full Construction Permit (Addition/Alteration) fees. Sewer capacity charges may apply (King County: ~$8k-$10k). Apply via https://www.piercecountywa.gov/PALS. Town (~590 residents) — permits via Pierce County PALS. | 30–120 days | Cite verified 2026-04-29 |
Town of Eatonville city | Yes | WA HB 1337 (effective 2024) requires cities ≥6,000 pop. to allow 2 ADUs per lot in residential zones, max 1,000 sq ft, no owner-occupancy requirement, no parking requirement near transit. Local size + design caps apply. | Full Construction Permit (Addition/Alteration) fees. Sewer capacity charges may apply (King County: ~$8k-$10k). Apply via https://www.piercecountywa.gov/PALS. Town — permits via Pierce County PALS. | 30–120 days | Cite verified 2026-04-29 |
Town of Ruston city | Yes | WA HB 1337 (effective 2024) requires cities ≥6,000 pop. to allow 2 ADUs per lot in residential zones, max 1,000 sq ft, no owner-occupancy requirement, no parking requirement near transit. Local size + design caps apply. | Full Construction Permit (Addition/Alteration) fees. Sewer capacity charges may apply (King County: ~$8k-$10k). Apply via https://www.piercecountywa.gov/PALS. Permits via Pierce County PALS. | 30–120 days | Cite verified 2026-04-29 |
Town of South Prairie city | Yes | WA HB 1337 (effective 2024) requires cities ≥6,000 pop. to allow 2 ADUs per lot in residential zones, max 1,000 sq ft, no owner-occupancy requirement, no parking requirement near transit. Local size + design caps apply. | Full Construction Permit (Addition/Alteration) fees. Sewer capacity charges may apply (King County: ~$8k-$10k). Apply via https://www.piercecountywa.gov/PALS. Town — permits via Pierce County PALS. | 30–120 days | Cite verified 2026-04-29 |
Town of Steilacoom city | Yes | WA HB 1337 (effective 2024) requires cities ≥6,000 pop. to allow 2 ADUs per lot in residential zones, max 1,000 sq ft, no owner-occupancy requirement, no parking requirement near transit. Local size + design caps apply. | Full Construction Permit (Addition/Alteration) fees. Sewer capacity charges may apply (King County: ~$8k-$10k). Apply via https://townofsteilacoom.org. Steilacoom runs its own permit center. | 30–120 days | Cite verified 2026-04-29 |
Town of Wilkeson city | Yes | WA HB 1337 (effective 2024) requires cities ≥6,000 pop. to allow 2 ADUs per lot in residential zones, max 1,000 sq ft, no owner-occupancy requirement, no parking requirement near transit. Local size + design caps apply. | Full Construction Permit (Addition/Alteration) fees. Sewer capacity charges may apply (King County: ~$8k-$10k). Apply via https://www.piercecountywa.gov/PALS. Town (~480 residents) — permits via Pierce County PALS. | 30–120 days | Cite verified 2026-04-29 |
Snohomish County
| Jurisdiction | Permit? | Threshold | Fee | Review days | Source |
|---|---|---|---|---|---|
City of Arlington city | Yes | WA HB 1337 (effective 2024) requires cities ≥6,000 pop. to allow 2 ADUs per lot in residential zones, max 1,000 sq ft, no owner-occupancy requirement, no parking requirement near transit. Local size + design caps apply. | Full Construction Permit (Addition/Alteration) fees. Sewer capacity charges may apply (King County: ~$8k-$10k). Apply via https://arlingtonwa.gov. Arlington Community + Economic Development. | 30–120 days | Cite verified 2026-04-26 |
City of Bothell city | Yes | WA HB 1337 (effective 2024) requires cities ≥6,000 pop. to allow 2 ADUs per lot in residential zones, max 1,000 sq ft, no owner-occupancy requirement, no parking requirement near transit. Local size + design caps apply. | Full Construction Permit (Addition/Alteration) fees. Sewer capacity charges may apply (King County: ~$8k-$10k). Apply via https://mybuildingpermit.com. Apply via MyBuildingPermit.com. | 30–120 days | Cite verified 2026-04-26 |
City of Brier city | Yes | WA HB 1337 (effective 2024) requires cities ≥6,000 pop. to allow 2 ADUs per lot in residential zones, max 1,000 sq ft, no owner-occupancy requirement, no parking requirement near transit. Local size + design caps apply. | Full Construction Permit (Addition/Alteration) fees. Sewer capacity charges may apply (King County: ~$8k-$10k). Apply via https://www.ci.brier.wa.us. Brier runs its own permit center. | 30–120 days | Cite verified 2026-04-29 |
City of Edmonds city | Yes | WA HB 1337 (effective 2024) requires cities ≥6,000 pop. to allow 2 ADUs per lot in residential zones, max 1,000 sq ft, no owner-occupancy requirement, no parking requirement near transit. Local size + design caps apply. | Full Construction Permit (Addition/Alteration) fees. Sewer capacity charges may apply (King County: ~$8k-$10k). Apply via https://mybuildingpermit.com. Apply via MyBuildingPermit.com. | 30–90 days | Cite verified 2026-04-26 |
City of Everett city | Yes | WA HB 1337 (effective 2024) requires cities ≥6,000 pop. to allow 2 ADUs per lot in residential zones, max 1,000 sq ft, no owner-occupancy requirement, no parking requirement near transit. Local size + design caps apply. | Full Construction Permit (Addition/Alteration) fees. Sewer capacity charges may apply (King County: ~$8k-$10k). | 30–90 days | Cite verified 2026-04-26 |
City of Gold Bar city | Yes | WA HB 1337 (effective 2024) requires cities ≥6,000 pop. to allow 2 ADUs per lot in residential zones, max 1,000 sq ft, no owner-occupancy requirement, no parking requirement near transit. Local size + design caps apply. | Full Construction Permit (Addition/Alteration) fees. Sewer capacity charges may apply (King County: ~$8k-$10k). Apply via https://snohomishcountywa.gov/319/Building-Permit-Information. Permits via Snohomish County. | 30–120 days | Cite verified 2026-04-29 |
City of Granite Falls city | Yes | WA HB 1337 (effective 2024) requires cities ≥6,000 pop. to allow 2 ADUs per lot in residential zones, max 1,000 sq ft, no owner-occupancy requirement, no parking requirement near transit. Local size + design caps apply. | Full Construction Permit (Addition/Alteration) fees. Sewer capacity charges may apply (King County: ~$8k-$10k). Apply via https://snohomishcountywa.gov/319/Building-Permit-Information. Permits via Snohomish County. | 30–120 days | Cite verified 2026-04-29 |
City of Lake Stevens city | Yes | WA HB 1337 (effective 2024) requires cities ≥6,000 pop. to allow 2 ADUs per lot in residential zones, max 1,000 sq ft, no owner-occupancy requirement, no parking requirement near transit. Local size + design caps apply. | Full Construction Permit (Addition/Alteration) fees. Sewer capacity charges may apply (King County: ~$8k-$10k). Apply via https://www.lakestevenswa.gov. Lake Stevens runs its own permit center. | 30–120 days | Cite verified 2026-04-29 |
City of Lynnwood city | Pending verification | — | — | — | Portal |
City of Marysville city | Yes | WA HB 1337 (effective 2024) requires cities ≥6,000 pop. to allow 2 ADUs per lot in residential zones, max 1,000 sq ft, no owner-occupancy requirement, no parking requirement near transit. Local size + design caps apply. | Full Construction Permit (Addition/Alteration) fees. Sewer capacity charges may apply (King County: ~$8k-$10k). Apply via https://marysvillewa.gov/permits. Marysville Community Development. | 30–120 days | Cite verified 2026-04-26 |
City of Mill Creek city | Yes | WA HB 1337 (effective 2024) requires cities ≥6,000 pop. to allow 2 ADUs per lot in residential zones, max 1,000 sq ft, no owner-occupancy requirement, no parking requirement near transit. Local size + design caps apply. | Full Construction Permit (Addition/Alteration) fees. Sewer capacity charges may apply (King County: ~$8k-$10k). Apply via https://mybuildingpermit.com. Apply via MyBuildingPermit.com. | 30–120 days | Cite verified 2026-04-26 |
City of Monroe city | Yes | WA HB 1337 (effective 2024) requires cities ≥6,000 pop. to allow 2 ADUs per lot in residential zones, max 1,000 sq ft, no owner-occupancy requirement, no parking requirement near transit. Local size + design caps apply. | Full Construction Permit (Addition/Alteration) fees. Sewer capacity charges may apply (King County: ~$8k-$10k). Apply via https://monroewa.gov. Monroe uses local permit center. | 30–120 days | Cite verified 2026-04-26 |
City of Mukilteo city | Yes | WA HB 1337 (effective 2024) requires cities ≥6,000 pop. to allow 2 ADUs per lot in residential zones, max 1,000 sq ft, no owner-occupancy requirement, no parking requirement near transit. Local size + design caps apply. | Full Construction Permit (Addition/Alteration) fees. Sewer capacity charges may apply (King County: ~$8k-$10k). Apply via https://mukilteowa.gov. Mukilteo uses local permit center. | 30–120 days | Cite verified 2026-04-26 |
City of Snohomish city | Yes | WA HB 1337 (effective 2024) requires cities ≥6,000 pop. to allow 2 ADUs per lot in residential zones, max 1,000 sq ft, no owner-occupancy requirement, no parking requirement near transit. Local size + design caps apply. | Full Construction Permit (Addition/Alteration) fees. Sewer capacity charges may apply (King County: ~$8k-$10k). Apply via https://www.snohomishwa.gov. City of Snohomish runs its own permit center. | 30–120 days | Cite verified 2026-04-29 |
City of Stanwood city | Yes | WA HB 1337 (effective 2024) requires cities ≥6,000 pop. to allow 2 ADUs per lot in residential zones, max 1,000 sq ft, no owner-occupancy requirement, no parking requirement near transit. Local size + design caps apply. | Full Construction Permit (Addition/Alteration) fees. Sewer capacity charges may apply (King County: ~$8k-$10k). Apply via https://www.stanwoodwa.org. Stanwood runs its own permit center. | 30–120 days | Cite verified 2026-04-29 |
City of Sultan city | Yes | WA HB 1337 (effective 2024) requires cities ≥6,000 pop. to allow 2 ADUs per lot in residential zones, max 1,000 sq ft, no owner-occupancy requirement, no parking requirement near transit. Local size + design caps apply. | Full Construction Permit (Addition/Alteration) fees. Sewer capacity charges may apply (King County: ~$8k-$10k). Apply via https://snohomishcountywa.gov/319/Building-Permit-Information. Permits via Snohomish County. | 30–120 days | Cite verified 2026-04-29 |
Snohomish County (unincorporated) county | Yes | WA HB 1337 (effective 2024) requires cities ≥6,000 pop. to allow 2 ADUs per lot in residential zones, max 1,000 sq ft, no owner-occupancy requirement, no parking requirement near transit. Local size + design caps apply. | Full Construction Permit (Addition/Alteration) fees. Sewer capacity charges may apply (King County: ~$8k-$10k). Apply via https://snohomishcountywa.gov/319/Building-Permit-Information. Snohomish County Planning & Development Services. Phone (425) 388-3311. | 30–90 days | Cite verified 2026-04-26 |
Town of Darrington city | Yes | WA HB 1337 (effective 2024) requires cities ≥6,000 pop. to allow 2 ADUs per lot in residential zones, max 1,000 sq ft, no owner-occupancy requirement, no parking requirement near transit. Local size + design caps apply. | Full Construction Permit (Addition/Alteration) fees. Sewer capacity charges may apply (King County: ~$8k-$10k). Apply via https://snohomishcountywa.gov/319/Building-Permit-Information. Town — permits via Snohomish County. | 30–120 days | Cite verified 2026-04-29 |
Town of Index city | Yes | WA HB 1337 (effective 2024) requires cities ≥6,000 pop. to allow 2 ADUs per lot in residential zones, max 1,000 sq ft, no owner-occupancy requirement, no parking requirement near transit. Local size + design caps apply. | Full Construction Permit (Addition/Alteration) fees. Sewer capacity charges may apply (King County: ~$8k-$10k). Apply via https://snohomishcountywa.gov/319/Building-Permit-Information. Town (~155 residents) — permits via Snohomish County. | 30–120 days | Cite verified 2026-04-29 |
Town of Woodway city | Yes | WA HB 1337 (effective 2024) requires cities ≥6,000 pop. to allow 2 ADUs per lot in residential zones, max 1,000 sq ft, no owner-occupancy requirement, no parking requirement near transit. Local size + design caps apply. | Full Construction Permit (Addition/Alteration) fees. Sewer capacity charges may apply (King County: ~$8k-$10k). Apply via https://snohomishcountywa.gov/319/Building-Permit-Information. Town — permits via Snohomish County. | 30–120 days | Cite verified 2026-04-29 |
How this table is built
Each row reflects the most-recently-verified authoritative rule on file for that jurisdiction and project type. “Pending verification” means we have the jurisdiction in our database but haven't yet personally checked the city page for ADU rules — those rows fall back to county or WA-state baselines until verified. Sources link directly to the city or county page we read on the verified-on date. See our data-quality leaderboard for how we keep these current.