Off-Grid Living in Missoula County, Montana

If you're eyeing off-grid land in Missoula County, Montana, here's what I found digging through the county, city, and state rules. This is research, not legal advice, so treat the office contacts below as your next call before you buy land or start building.

Zoning is a patchwork. Missoula County has both zoned and unzoned unincorporated areas, and each works differently: land in a zoned district needs a zoning compliance permit from the county's Planning, Development & Sustainability office, while land in an unzoned area needs a land use permit instead. If your parcel is inside Missoula city limits, none of the county rules apply at all, the city runs its own Unified Development Code (Title 22) through its Development Services office.

No official "tiny home" category exists here. The county's building guide treats new residential construction on the standard building/zoning track. I did find that the county exempts some small structures from building permits altogether, things like storage buildings under 200 square feet, greenhouses, low decks, gazebos, and additions with no habitable space. But claims I saw elsewhere about specific tiny-home or ADU square-footage thresholds came only from commercial "guide" sites, not the county itself, so I'm flagging those as not confirmed.

Building permits are required in the county, which is notable because Montana law lets counties exempt single-family homes from permitting, and Missoula County chose not to take that exemption (though commissioners later carved out some smaller structures). Even permit-exempt structures still typically need separate zoning, floodplain, plumbing, mechanical, or electrical sign-off.

Septic is tightly controlled by the county Health Code, administered by the Missoula City-County Health Department, on top of state DEQ minimums. Any occupied structure needs approved toilet facilities, any structure with running water needs a permitted septic system or sewer connection, and a septic permit must be fully issued before the county will issue your building permit. There's a required four-foot separation between drainfield and groundwater. Composting toilets aren't addressed separately in what I found, so confirm with the Health Department's Land Sanitarian if that's your plan.

Greywater and rainwater harvesting have no county-specific rules that I could locate. That likely means the state's general baseline applies, but I'd call the Health Department to be sure before designing a system.

Wells are permitted, and most off-grid setups qualify as "exempt wells" under state law (10 acre-feet/year or less, 35 gpm or less). Starting in 2026, the state DNRC will require a Notice of Intent filing before using water from a new exempt well, a real change worth knowing before you drill. The county also cross-checks well and septic siting distances during permitting.

Full utility disconnection isn't explicitly banned, but occupancy still hinges on having an approved water source and wastewater system, so "off-grid" doesn't mean "unregulated" here.