Off-Grid Living in Petroleum County, Montana

Petroleum County is Montana's least populous county, and that shows up clearly in its online presence: I could not find a dedicated zoning ordinance, planning department, or building code page for the county. That doesn't mean "anything goes," but it does mean a lot of what applies to you here is the state baseline rather than a local rulebook.

Zoning and raw land. I found no evidence of a countywide zoning resolution or map. Montana counties only get zoning if they adopt it themselves, and very small, sparsely populated counties like Petroleum often haven't bothered. I'd call this "not confirmed" rather than "no zoning," though, since the only way to know for sure is to ask the County Clerk & Recorder's office directly.

Dwellings, tiny homes, RVs. No county-specific occupancy rule turned up. Absent local rules, the state baseline applies: foundation-built tiny homes generally fall under IRC Appendix Q, while RV-titled tiny homes are treated as RVs, not permanent dwellings.

Building permits. Montana requires a state building permit for many types of construction, but single-family homes are typically exempt from state permit jurisdiction unless the county has adopted its own building code. I found no evidence Petroleum County has done so, which likely means single-family dwellings here fall under that state-law exemption. Confirm this directly with the state Building Codes Bureau or the county clerk, since I couldn't verify it from a county source.

Septic. This one is more settled. Petroleum County doesn't run its own environmental health office; it's served by the Central Montana Health District, which covers Petroleum along with Golden Valley, Judith Basin, Musselshell, and Wheatland counties. That district's sanitarian handles septic system permitting and inspection under Montana DEQ standards. Composting toilets aren't separately addressed anywhere I found, so I'd assume they fall under the same state DEQ minimum standards enforced by the district.

Greywater and rainwater. No local rules found for either. State ARM rules apply by default: greywater reuse inside the home is generally allowed without a permit, though subsurface irrigation use is more restricted, and rainwater harvesting for personal, non-potable use is generally permitted.

Wells. No Petroleum County water authority page exists that I could find. Exempt-well filings and water rights are handled by the state Department of Natural Resources and Conservation (DNRC) statewide, including here.

Utility disconnection. No ordinance requiring hookup to grid, water, or sewer was found. Any such requirement would more likely show up through subdivision review under the state's Sanitation in Subdivisions Act, or through a building permit process, rather than as a standalone rule, and I found no sign the county has adopted anything like that.

Bottom line: Petroleum County has an unusually thin official web footprint, so a lot of this defaults to state rules. The county clerk's office is genuinely your best first call for zoning and building questions.