Off-Grid Living in Madison County, Montana

I've spent a while digging through Madison County, Montana's planning and health department pages, and the honest headline is: this is a county with a lot of room to build off-grid, but with real gaps in the public record that you'll need to close with a phone call before you buy land or break ground.

Zoning. Madison County does not have a county-wide zoning ordinance. What it has instead is a Growth Policy, which the county itself says is a planning guide, not a regulatory document, so it can't be used to approve or deny a project. That said, Montana law allows small groups of landowners to petition for targeted zoning districts, so a specific pocket of the county could have its own zoning even though the county at large doesn't. Before you count on "no zoning," call the Madison County Planning Department and ask about your specific parcel.

Dwellings, tiny homes, and RVs. I could not find county-specific ordinance text addressing tiny homes, THOWs, or RV living. Montana has adopted Appendix Q as a state-level option for small foundation-built homes, and RVs are generally treated by their own classification rather than as dwellings, but Madison County hasn't published its own local interpretation that I could find. Planning is your point of contact here, and this is genuinely unconfirmed territory.

Building permits. The county's Building Department does require a permit, and it has adopted a state IRC edition. There's an age restriction on manufactured/mobile homes moved into the county, and notably, Planning and Inspections wants to see that you can get an approved septic system before they'll issue a building permit at all, so septic and building approvals are linked in practice. I also saw a county rule limiting land to two dwellings per tract.

Septic. This is the county's most clearly documented rule. A permit is required for any septic or wastewater system, installation must be done by a Madison County Licensed Installer, and any regularly occupied structure producing wastewater needs a permitted individual or multi-user system, with narrow exceptions for pre-1991 systems or connections to a DEQ-approved public sewage system. Composting toilets aren't addressed separately in what I found, so don't assume one satisfies this requirement on its own; ask Environmental Health.

Greywater and rainwater. Neither is separately regulated at the county level as far as I could find. That leaves you falling back to Montana's state default, which is generally permissive for indoor greywater reuse and rooftop rainwater collection, with more caution around subsurface greywater irrigation. Treat this as unconfirmed for Madison County specifically.

Wells. Well drilling itself is a state DNRC matter, not a county one. But if you're also getting a septic permit, the county will require a water sample from your well (nitrates and specific conductance) as part of that application.

Off-grid utilities. I found no county requirement that you connect to grid power. But going off-grid doesn't get you out of the wastewater permit requirement, that one applies regardless of your electrical setup.

Bottom line: Madison County is workable for off-grid living, especially since there's no blanket zoning, but septic is the load-bearing regulation here, and tiny home/RV/greywater rules need direct confirmation from the county.