Seattle’s ADU rules changed in 2025 and again in January 2026, and some older city tip sheets have not caught up. Here is what changed and how to check a source.

A backyard cottage needs its own address so responders, utilities and mail can find it. Here is how SDCI assigns one and what the owner handles afterward.

A permit lets work start, but only a passed final lets anyone move in. Here is the usual order of Seattle inspections and how trade finals fit around them.

Nobody can promise how long a Seattle cottage permit will take, but the phases are predictable. Here is what moves each one faster or slower and how to track it.

Most Seattle cottage permits get at least one correction notice. Here is why reviewers ask for changes and how SDCI wants each comment answered and uploaded.

Pre-approved cottage plans on ADUniverse speed up review of the building itself, but your lot still needs site checks. Here is who qualifies and what you still submit.

A Seattle DADU application mixes owner records, signed forms and professional drawings. Here is what SDCI asks for at intake and who usually supplies each item.

Once your plans reach SDCI, several review teams check zoning, structure, energy, drainage and life safety. Here is how the stages and correction rounds work.

A backyard cottage in Seattle needs one main SDCI permit, but trade permits, utility approvals and site reviews usually follow. Here is who handles each piece.