Seattle treats the permit record as central to an accessory dwelling unit’s legal status. The City’s ADU guidance says an attached or detached unit is not legal unless it has been established through a permit process. For a unit that already exists, Seattle identifies a construction permit to establish use. That is a different permit type from the construction addition or alteration permit the City describes for creating a new attached or detached unit.
Identify the existing unit and permit question
Start with the property’s address and determine whether the unit is attached or detached, where it sits on the lot, and whether it was created inside an existing building or as a separate structure. Seattle’s guidance distinguishes those configurations and notes that applicable zoning, location, height, and building-code requirements still matter. Do not assume that a permit for the main house or another project includes the ADU; compare the permit scope and approved plans with the unit as it exists.
If the unit has no known permit, ask Seattle Department of Construction and Inspections (SDCI) about the construction permit to establish use and what records, plans, review, and inspections apply to this property. The published ADU page identifies the permit route but does not determine whether a particular unit can meet current requirements or receive approval.
Check the approval record and separate services
Use the City’s project and permit records to locate the relevant application and decision. Verify the address, structure, approved use, work scope, conditions, and inspection or completion status. A record number or application is not itself proof that the unit was approved for its current configuration and use. If records are incomplete, request the underlying file or written clarification from SDCI.
Seattle’s ADU guidance also notes that an electrical service change or new service from Seattle City Light may be needed. This is a separate utility question; a permit to establish use does not by itself confirm electrical capacity or service approval. Zoning, building-code, environmental, shoreline, and other requirements may also apply according to the site and work.
Keep the result property-specific
Ask SDCI which current forms, drawings, code requirements, fees, and inspections apply before relying on a route. Match any issued permit and final record to the address, unit, approved plans, and completed work. A permit route is not a promise of approval, and this guide cannot determine the status of an individual Seattle property. For a broader records method, see how to check whether an existing ADU is legally recognized and how retrospective approval can work.