ADUAllowed

Seattle, WA

Seattle ADU Permit Check.

Seattle requires a construction permit to build an attached ADU, build a detached ADU, or legalize an existing unpermitted ADU.

Start typing for address, city, county, or state suggestions.

ADU eligibility screen

Seattle requires a construction permit to build an attached ADU, build a detached ADU, or legalize an existing unpermitted ADU.

Seattle accessory dwelling units High confidence
ADU eligibility screen

Seattle requires a construction permit to build an attached ADU, build a detached ADU, or legalize an existing unpermitted ADU.

This answers the permit requirement, not approval of a specific parcel or design. Land-use, lot, tree, environmentally critical-area, utility, fire, and building-code rules remain.

What this tells youComputed rule answer
How precise this isComputed rule answer
Official data checkedSeattle accessory dwelling units
Next stepCheck parcel rules and project scope before design, purchase, or contractor conversations.
Attached ADUConstruction permit required
Detached or legalizationConstruction permit required
Still verifyLand use, lot, trees, ECA, utilities, fire access, and building code
Confidence: HighComputed rule answerReviewed jurisdiction ruleReviewed July 2026
Seattle accessory dwelling unitsOfficial source
dadusdciexact answerofficial rulereviewed threshold

Related ADUAllowed checks

Nearby and similar official-source routes.

Spokane, WATacoma, WAVancouver, WABellevue, WA

Common questions

What source does ADUAllowed use for Seattle, WA?

Seattle accessory dwelling units. Official agency pages remain final.

Can I act on this ADUAllowed result without checking the agency?

No. This answers the permit requirement, not approval of a specific parcel or design. Land-use, lot, tree, environmentally critical-area, utility, fire, and building-code rules remain. Use the official source link before making a legal, safety, construction, property, or financial decision.