King County contains Seattle plus a large number of independent cities plus substantial unincorporated territory. Each of those categories permits differently, and homeowners regularly start in the wrong place.
The three categories
Seattle. The Seattle Department of Construction and Inspections handles everything within city limits.
Other incorporated cities. Bellevue, Kent, Renton, Federal Way, Kirkland, Redmond, Auburn, Sammamish, Issaquah, Shoreline, Burien, Des Moines, Kenmore, Mercer Island, SeaTac, Enumclaw and others each operate their own permit departments with their own processes, fees and timelines.
Unincorporated King County. Areas not within any city boundary go through the King County Permitting Division.
Finding out which applies
Most people know whether they live in Seattle. The genuinely ambiguous case is unincorporated territory, because a postal address frequently carries a city name for mail purposes while the property sits outside that city’s boundary.
A property with a Renton mailing address may be in unincorporated King County. Your property tax records and the county parcel viewer will tell you definitively, and it is worth establishing before a project rather than during one.
Why the difference matters
Fees differ. Review timelines differ. Required documentation differs. Some jurisdictions run online submission efficiently; others are slower. Inspection scheduling varies.
None of that changes whether you need a permit, but all of it changes how long the project takes and what it costs. Building a schedule on the assumption that Bellevue’s process resembles Seattle’s produces a schedule that does not hold.
The contractor question
This is a genuinely useful screening question when hiring. Ask a contractor which authority permits work at your address. Someone who works your area regularly answers immediately. Someone who hesitates, or who names the county for a property inside a city, has told you something about their local experience.
It also matters for scheduling. A contractor familiar with your jurisdiction’s process gives more realistic timelines, because they have been through it recently.
Where state-level programmes apply
Not everything runs through the local building department. Electrical work in Washington is generally permitted and inspected through the state’s electrical programme rather than the city, which surprises homeowners who assume one office handles everything.
Your contractor should know which route applies to which element of the work. On a project involving structural, electrical and plumbing elements, more than one process may be running at once.
Confirm rather than assume
Requirements and processes change. Anything material to your project is worth confirming with the relevant authority directly, or having your contractor confirm in writing. A general guide tells you where to look; it cannot tell you what is current at your address today.