Sammamish, WA Accessory Structures: Tiny Homes (2026)

Sammamish does not publish a tiny-home-specific code. A permanent, site-built tiny house on a foundation is regulated as a detached accessory dwelling unit (ADU), which the city limits to a maximum of 1,000 square feet. Sammamish allows up to two ADUs on a lot with a detached single-family residence (two attached, two detached, or one of each), and ADUs do not count toward the home's Floor Area Ratio. No additional parking is required when the property already has four or more parking spaces. Detached-ADU standards include a 24-foot height limit and reduced setbacks (rear and side as low as 5 feet), under standards the city cites to SMC 21.05.010.C (footnote 5). Washington's statewide ADU law, HB 1337 (RCW 36.70A.681), reinforces this by requiring planning cities to allow at least two ADUs per single-family lot in urban growth areas, prohibiting maximum-size caps below 1,000 square feet, and barring height limits under 24 feet. A tiny house on wheels (a recreational-vehicle-type structure) is generally not recognized as a permanent dwelling and cannot be used as a primary residence on a residential lot the way a foundation-built ADU can. Confirm classification and building-code requirements with the Sammamish Permit Center before proceeding.