Building permits, zoning and land rules in Musselshell County, Montana

A private home or apartment with 4 or fewer units that does not serve transient guests is exempt from the state building permit in unincorporated Musselshell County¹. Farm and ranch buildings are also exempt from state building permits¹¹. Inside Roundup, city building permits are required for fences, additions and new construction². Montana’s adopted codes and separate trade-permit rules still need attention; the 2024 codes took effect September 26, 2026^11,12. For non-exempt projects, obtain the state building permit before construction and before trade permits are issued¹¹. Submit construction plans and a Building Permit/Plan Review Application, resolve review comments and pay both fees before issuance¹¹. The state plan-review fee is 35% of the building permit fee¹. State building-permit holders must request required inspections and provide access when work is ready¹¹.

The Montana Building Codes Program handles covered projects in Musselshell County and answers questions about separate trade permits^12,13. Call the program at (406) 841-2056 or email buildingcodes@mt.gov; its office is at 2705 Skyway Drive, Helena MT¹³. Musselshell County uses contract sanitarians for septic and subdivision review and directs applicants to its main line for routing; the published survey-review contact is the County Sanitarian at (406) 535-7466 or sanitarian2@co.fergus.mt.us^6,14. For mapped flood-hazard questions, contact Musselshell County Floodplain Administration at 406-323-2777, 12 Main St • Roundup, MT 59072¹⁵. A new or modified approach onto a Montana state highway requires an approach permit or right-of-way agreement¹⁶. We could not confirm a county-road driveway permit requirement; ask the Musselshell County Road Department before building an approach.

Unincorporated Musselshell County has no county zoning ordinance or county zoning districts⁴. Zoning varies across Musselshell County because incorporated land follows a different authority⁴. Inside Roundup, the city administers zoning and requires building permits for fences, additions and new construction^2,3. County contract sanitarians handle rural septic review; Roundup prohibits additional onsite septic installations^6,7. On unincorporated land, county zoning imposes no minimum dwelling size, minimum lot size, general setback, lot-coverage limit or building-height limit⁴. County zoning also does not restrict manufactured-home occupancy or an accessory dwelling there, but sanitation, subdivision, floodplain, access and applicable state building-code rules remain separate⁴.

A local health-department drainfield permit is required before drainfield installation on rural Musselshell County land, even when a certificate of subdivision approval exists⁵. Musselshell County uses contract sanitarians for septic and subdivision review, while Montana DEQ handles state sanitation approval and subdivision review⁶. Start with the County Sanitarian before excavation and ask which inspection stages apply because we could not confirm a published local inspection schedule¹⁴. Soil conditions deserve early attention: only 19.9% of Musselshell County soils are rated without severe limitations for a conventional septic drain field¹⁷. A parcel division adds formal review by the County Examining Land Surveyor and County Sanitarian¹⁸. Inside Roundup, additional septic tanks, cesspools, cisterns and privy vaults are prohibited; a rural drainfield permit does not establish permission for a new city installation⁷.

Unincorporated Musselshell County has no county-zoning restriction on RV occupancy or temporary camping on private land⁴. Unincorporated Musselshell County likewise has no county-zoning restriction on tiny-home occupancy and no zoning-based minimum dwelling size⁴. Those are zoning answers, not exemptions from septic, subdivision, floodplain, access or state building-code rules⁴. A drainfield still requires a local permit, so give the County Sanitarian the proposed wastewater arrangement before occupying an RV or tiny home^5,14. We could not confirm a general rule for alternative off-grid sanitation; ask the County Sanitarian about the proposed system¹⁴. Inside Roundup, city zoning applies and additional septic installations are prohibited^3,7.

1. Confirm the parcel is in unincorporated Musselshell County rather than Roundup, which has city building permits and zoning^2,3.

1. Contact the contract County Sanitarian before choosing the homesite, obtain the required drainfield permit and ask which inspections apply^5,6,14.

1. If a well will use more than 35 gallons per minute or 10 acre-feet per year, obtain the required water permit; smaller uses may qualify for an exception and current notice requirements¹⁰.

1. Ask County Floodplain Administration whether the homesite is in a designated Special Flood Hazard Area; new development there requires a local floodplain development permit^15,19.

1. Obtain an approach permit or right-of-way agreement if the driveway meets a Montana state highway¹⁶.

1. Confirm the residential exemption and separate trade permits with the Montana Building Codes Program; for covered work, submit plans before construction and request inspections when ready^11,13.

1. If doing plumbing yourself, use the homeowner exemption only for your personal-use residence, not speculative resale or rental, and request inspection before covering plumbing; obtain a state homeowner’s electrical permit before wiring your home^8,9.

Water and wastewater feasibility come first. Musselshell County averages about 15.1 inches of precipitation annually, and severe drought occurs in about 11.4% of years¹⁷. A groundwater use above 35 gallons per minute or 10 acre-feet per year requires a water permit, while qualifying smaller uses may use an exception subject to current notice requirements¹⁰. Only 19.9% of county soils are rated without severe limitations for a conventional septic drain field¹⁷. If a certificate of survey is involved, the Examining Land Surveyor and County Sanitarian perform preliminary review, and the $250 review fee is due at filing in addition to filing fees and supplemental documents¹⁸. Electronic and hard-copy submissions are accepted, and corrections must be completed before final filing¹⁸. Check flood hazards and legal access before closing^16,20. An agricultural-tract subdivision exemption requires covenant language on the survey and a landowner certificate citing the exemption; the farm-building permit exemption does not replace those survey requirements^11,21.