ADU rules in Yellowstone County, MT — also called accessory dwelling unit regulations or granny flat ordinances — cover setbacks, owner-occupancy, parking, and permit requirements.
In Yellowstone County's zoning area around Billings, "accessory living quarters" (guest houses) are allowed within an accessory building but may have no kitchen and may not be rented as a separate dwelling. A full second dwelling depends on the zoning district. Rural unzoned land sets no such rule.
Yellowstone County exercises zoning jurisdiction in the district around Billings and, through the adopted Zoning Ordinance (Title 17), defines "accessory living quarters" as quarters within an accessory building for family, employees or temporary guests only. The regulation states such quarters "have no kitchen facilities and are not rented, leased, or otherwise used as a separate dwelling unit" and includes the "guest house." A true rentable second dwelling (an ADU with a kitchen) is not authorized under this definition and would require a permitted multifamily use in the district. On unzoned rural county land, the county sets no ADU rule and defers to state building code and septic (DEQ) approval. Confirm your parcel's district with County/City-County Planning.
Building or renting a non-conforming accessory dwelling in the zoning area is a zoning violation handled by County Code Enforcement (406-652-2050); remedies include permit denial and orders to remove unpermitted living quarters.
Other ordinances people look up for this city. Green dot = verified primary-source excerpt.
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