Bonner County, ID Accessory Structures: ADU Rules (2026)

Bonner County Revised Code § 12-490 states two intents: to provide affordable housing opportunities throughout the county, and to limit the visual and physical impact of an accessory dwelling unit on surrounding properties and the local infrastructure. The standards then set hard numbers.

Size and occupancy: an accessory dwelling unit cannot exceed nine hundred (900) square feet and cannot have more than two (2) bedrooms. Count: no more than one accessory dwelling unit is permitted on a property. Parking: one additional off street parking space is required for the unit.

Form: the unit can be attached to the primary dwelling or detached, with one exception tied to lot size. On any lot less than twenty thousand (20,000) square feet, the accessory dwelling unit must be attached to the primary structure or located above or attached to a garage. That rule is how a garage apartment fits the code on a small lot, while a freestanding cottage is available only on larger lots. Entrance: the unit must have a separate outside entrance from the primary structure.

Setbacks: subsection B.7 makes accessory dwelling units subject to the same setbacks as a regular dwelling unit, so the setback figures for the zoning district in Title 12 apply rather than the smaller accessory building setbacks. The section was adopted in Ordinance 501 and amended by Ordinances 512, 520 and 607, the latest on July 22, 2020. The standards apply in unincorporated Bonner County. Sandpoint, Ponderay, Priest River and the other incorporated cities set their own ADU rules, and each ADU is also subject to the building permit process of the Bonner County Building Department.