You’ll also want to peruse one of these “Tips” publications from the City of Seattle: “Establishing An Attached Accessory Dwelling Unit” or “Establishing A Backyard Cottage.” From these publications (as of May 2015), we’ve distilled a few answers to frequently asked questions:
Q: Does my main house or ADU/Backyard Cottage need to be owner occupied?
A: Yes. For at least six months of the year, either the main house or the ADU/Backyard Cottage need to be your main and permanent residence.
Q: How big can my ADU or Backyard Cottage be?
A: Attached ADUs can be 1000 square feet or smaller (with a couple exceptions) for single family homes. For rowhouses and townhomes, Attached ADUs can be no larger than 650 square feet and may not exceed 40% of gross floor area. Backyard Cottages can be 800 square feet or smaller, including garage and storage areas.
Q: Do I have to provide parking for my ADU or Backyard Cottage?
A: Yes, one off-street parking space is required, except in some urban villages and urban centers, or in lowrise zones.
Q: How large does my lot need to be to allow a Backyard Cottage?
A: At least 4000 square feet.
Q: How much does it cost to build an ADU or Backyard Cottage in Seattle?
A: See our post, “How Much Does It Cost To Build An ADU?”
Q: What else should I consider?
A: See our post, “ADU 101.”
Good luck with your project. Please contact us if you’d like us to build it!Back to Field Notes