Off-grid living in Montana: a property guide
A single-family house may be exempt from Montana’s state building permit in the state-administered area. Certified local jurisdictions can require permits, trade permits still need checking, and water and sanitation have separate approval systems.
“You don’t need a building permit in rural Montana.”
First locate the property against the certified local-government list. A single-family residence in the state program’s territory may be exempt from a state building permit, but local building authority, plumbing/electrical/mechanical permits, zoning, sanitation, water rights, floodplain and final-use requirements must still be resolved.
2026 water-right change
An “exempt well” now starts with notice and authorization.
Beginning January 1, 2026, a person intending to use the groundwater permit exception must submit Form 602I and receive DNRC authorization before putting the water to use. After authorized development, the user files the completion notice to receive the groundwater certificate.
- Notice of Intent DNRC reviews whether the proposed use qualifies.
- Five-year development window Complete and use the source substantially as authorized.
- Notice of Completion Establish the official groundwater right record.
The subdivision trap
Several small wells can become one combined appropriation.
Montana law prevents a larger groundwater development from being divided into multiple wells to evade the permit process. DNRC evaluates whether wells drawing from the same source form a combined appropriation. If their combined annual diversion exceeds ten acre-feet, the permit exception may not apply.
Current DNRC guidance also states that lots across phases of a multi-phase subdivision share the combined limit. A subdivision sanitation approval is not a guarantee of an individual water right.
A Certificate of Subdivision Approval is evidence—but read what it actually approves.
Montana DEQ describes a COSA as sanitation approval addressing water supply, sewage disposal, solid waste and storm drainage for the reviewed subdivision. Existing approval conditions, approved lot layout, water source and wastewater system must match the intended project.
Obtain the recorded plat and COSA, approved site plan, any amended approval, well/cistern conditions, septic location and sizing, nondegradation requirements, local health permit, and confirmation that the proposed dwelling and bedrooms fit.
Map the building-code jurisdiction discipline by discipline.
Montana certifies local city, county and town programs to enforce selected code disciplines within stated boundaries. Areas outside those programs fall to the state program, whose permit FAQ identifies the single-family state-building-permit exemption.
Check which of building, plumbing, electrical, mechanical, fire-suppression and other disciplines the jurisdiction enforces.
Ask the state about the residence exemption and every trade permit; do not infer electrical, plumbing or mechanical exemptions.
A groundwater certificate does not certify drinking water.
DNRC’s process establishes the legal water use. Montana’s public-health laboratory separately offers private-well chemistry and microbiology testing and warns that location and construction affect contamination vulnerability.
Well log, authorized notice/certificate, combined-appropriation status, pump/yield opinion, current bacteria and nitrate testing, geology-based metals screen, treatment design and seasonal storage.
RV residence and temporary living remain local property questions.
The statewide evidence reviewed does not create blanket permission to occupy an RV on private Montana land. County or municipal land use, sanitation, floodplain, road/fire access and recorded restrictions can distinguish storage, camping, construction occupancy and permanent use.
Provide unit type, dates, occupants, purpose, water, sewage, hookups and any home-construction permit to the planning and sanitation authorities. Ask each authority to cite the controlling rule.
Montana acquisition file
What “buildable” must include
Zone, legal parcel, allowed dwelling, density, setbacks, access and overlays.
Authorized notice, certificate/permit, combined analysis and intended-use match.
Well construction, yield, lab quality, treatment, power and drought storage.
COSA/plat conditions, septic approval, layout, reserve area and final inspection.
State/local jurisdiction, every trade, factory-built path and occupancy endpoint.
Legal access, road agreement, easements, covenants and utility obligations.
Evidence ledger
Official sources reviewed
Checked September 26, 2026. The page uses the 2026 Notice of Intent process and keeps state, local, sanitation and property evidence separate.
- 01Exempt Well Updates and Information
Montana DNRC · 2026 notice, thresholds and combined appropriation
- 02Apply for Water Rights
Montana DNRC · Permit and groundwater-certificate pathways
- 03Engineering Infrastructure & Subdivisions
Montana DEQ · COSA, water, wastewater, solid waste and drainage review
- 04Montana Building Codes Program
Montana Department of Labor & Industry · State codes, permits and inspections
- 05Building Permit FAQ
Montana Department of Labor & Industry · Single-family state exemption and local jurisdiction
- 06Certified Local Government Programs
Montana Department of Labor & Industry · Current code disciplines and jurisdiction boundaries
- 07Private Well Testing
Montana DPHHS Environmental Laboratory · Chemistry and microbiology testing resources