Accessory Structures in Yellowstone County, MT (2026)
5 county-level rules, plus city-specific rules for 1 city in Yellowstone County, Montana.
Verified from official government sources
ADU Rules
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.
Accessory Dwelling Unit Rules in Yellowstone County, MT
Some RestrictionsYellowstone County/Laurel Zoning Ordinance 17.08.030
"Accessory living quarters" means living quarters within an accessory building for the sole use of the family or of persons employed on the premises... Such quarters have no kitchen facilities and are not rented, leased, or otherwise used as a separate dwelling unit.
ADU Owner Occupancy
In unincorporated Yellowstone County, an accessory dwelling unit only gets approved if the property owner actually lives on site. The zoning code requires the owner to occupy either the primary home or the ADU as a principal residence at least six months a year and record a deed restriction saying so.
ADU Owner-Occupancy Rules in Yellowstone County
Significant RestrictionsYellowstone County Zoning Code § 27-1009.G.2(a)-(c)
2. Ownership and Occupancy (a) The property owner shall live in either the primary or accessory dwelling unit, with one of the units serving as their principal residency for at least six months in a year. No third party rentals shall occur in the owner-occupied unit. (b) The property owner shall record a deed restriction with the Yellowstone County Clerk and Recorder requiring owner-occupancy o...
Shed & Carport Rules
Yellowstone County's zoning ordinance has no separate carport standard; a carport is treated as an accessory building. In the zoning area around Billings that means rear-yard placement with at least a two-foot setback from lot lines and alley. On unzoned rural county land the county sets no rule.
Carport Rules in Yellowstone County, MT
Some RestrictionsYellowstone County/Laurel Zoning Ordinance 17.48.060(B)
In a residential district a detached garage on an inside lot may be located with the same setback from the street as required for the principal building; providing, that such detached garage does not violate the side yard requirements for a principal building for the district in which it is located.
Garage Conversions
In the county zoning area, a "private garage" is defined as an accessory building used only for storing motor vehicles. Converting it to a habitable rental unit creates a separate dwelling not authorized as an accessory use, and needs district, building and septic approval. Rural unzoned land sets no rule.
Garage Conversion Rules in Yellowstone County, MT
Some RestrictionsYellowstone County/Laurel Zoning Ordinance 17.08 (Private garage)
"Private garage" means an accessory building or part of principal building used only for the storage of motor vehicles as an accessory use, when the storage space does not exceed that for the following number of vehicles: For any single-family dwelling -- three passenger vehicles.
Tiny Homes
Yellowstone County's zoning code will not let a mobile home, manufactured home, RV, travel trailer, or any other wheeled or transportable structure count as an accessory dwelling unit. A tiny home on a permanent foundation can still qualify, but one that rolls in on a trailer chassis cannot.
Tiny Homes as ADUs Banned in Yellowstone County
Heavy RestrictionsYellowstone County Zoning Code § 27-1009.G.5(a)-(d)
5. Construction (a) Accessory dwelling units must contain a kitchen or a food prep area, bathroom, and sleeping area for the sole use of the unit. (b) Water and sewer service shall be provided through individual well or septic systems or a water and sewer district. The water and sewer district shall determine whether principal dwelling units and accessory dwelling units can share utilities. (c)...
Accessory Structures by City in Yellowstone County
1 cities in Yellowstone County have their own accessory structures rules. Each link goes to that city's dedicated page with code citations.
All Yellowstone County ordinances
See every category we cover for Yellowstone County: parking, noise, fences, fires, animals, pools, and more.
Yellowstone County Ordinance Hub →