Bothell, WA Accessory Structures: Shed & Carport Rules (2026)

BMC 12.14.130 covers storage buildings, detached private garages and every other accessory building in a residential zone in the City of Bothell. Each one must keep the same residential character as the primary structure, cover a maximum of five percent of the lot area, and stay at an exterior height no greater than 20 feet or the height of the primary building or structure, whichever is less. Detached accessory dwelling units are the exception and follow BMC 12.14.135, which exempts them from the five percent area limit.

Appearance rules sit in subsection A. Accessory buildings use similar siding, roofing and detailing as the primary structure, in a style that complements it. Metal buildings that are clearly of a different style than the house are not allowed once the accessory building is over 120 square feet. Subsection B applies to large buildings: a footprint greater than 1,200 square feet must be set back an additional foot from the required setback line for each 100 square feet of area above 1,200 square feet, and a minimum 10-foot-wide Type II landscape buffer goes between the building and any property line within 50 feet of it.

Subsection C ties height to distance from the rear lot line. At the five-foot accessory building rear setback line the maximum height is 10 feet, and it increases by one foot for each additional foot of setback until the maximum height allowed for accessory buildings is reached. The five-foot rear setback itself comes from BMC 12.14.070(B), which fixes rear yard setbacks for accessory buildings and structures other than detached accessory dwelling units at five feet in all residential zones. The section prints no permit threshold or exemption size, so permit questions go to the building official under the construction codes in BMC Title 20.