Building permits, zoning and septic rules in Ravalli County, Montana

A single-family home in unincorporated Ravalli County does not need a county building permit, and Montana exempts residential buildings containing fewer than five dwelling units from state building permits except when serving transient guests^1,2. Non-exempt construction needs a state building permit before work starts unless a certified local program has jurisdiction^1,2. Ravalli County is not listed as a certified county building-code program; areas outside certified local jurisdictions fall under the State Building Codes Bureau¹⁰. Separate electrical, plumbing or mechanical permits may still apply to an exempt house².

Ravalli County has no county building department issuing residential building permits¹. The Ravalli County Planning Department handles land-use planning, subdivision review and floodplain management; reach Planning at 406-375-6530 or planning@rc.mt.gov¹¹. For non-exempt work outside certified local jurisdictions, submit construction plans and the Building Permit/Plan Review Application to the Montana Building Codes Program, resolve review comments and pay the required fees before issuance^2,10. Ravalli County Environmental Health separately issues on-site wastewater permits and conducts site evaluations⁴.

Unincorporated Ravalli County has citizen-initiated zoning districts (CIZDs), with different standards in each district; adopted districts are enforceable by the county^3,6. County zoning resources include a district map and recorded documents, and land shown as unzoned is outside a CIZD with no CIZD development standards¹². A district may restrict lot size or future subdivision; in the Yerian-Mihara Voluntary Zoning District, all residences, structures and buildings must be at least 75 feet from property lines^7,13. Ask Planning to identify the parcel’s district and applicable standards; the recorded version in the Clerk and Recorder’s Office controls over differing electronic documents^3,11. Inside Hamilton and Stevensville, municipal zoning applies^14,15. County Environmental Health still handles on-site wastewater permits, and Hamilton additionally requires Public Works permission and prohibits permanent private septic systems^4,16.

Ravalli County Environmental Health is the county authority for wastewater-system permits⁴. A permit is required to install, alter, repair, use or connect to a wastewater system, and every new occupied building using an on-site wastewater system needs approval before any foundation is poured or non-concrete footing is installed⁵. Applications may be delivered in person or sent by fax, email or mail; every owner of record must sign, and the application needs a legal property address¹⁷. Fees must be paid before review, including a non-refundable $50 processing portion for listed wastewater applications and a $250 permit fee for a qualifying standard trench system¹⁸. Only 1.1% of Ravalli County soils avoid severe limitations for a conventional drain field, so settle septic feasibility before fixing the house site⁸.

We could not confirm a general rule for full-time RV or tiny-home occupancy on private land in unincorporated Ravalli County; ask the Planning Department about the parcel’s citizen-initiated zoning district and intended use^6,11. We also could not confirm countywide minimum dwelling size, manufactured-home occupancy, lot coverage or building height rules; district standards vary⁶. A new occupied building using an on-site wastewater system needs county approval before foundation work⁵. Campgrounds, RV parks and mobile-home parks renting or leasing spaces require subdivision review¹⁹. Within regulated parks, mobile homes and attached structures must be at least 25 feet from public roadway easements, 15 feet from park boundaries and 10 feet from the directly serving roadway and other mobile homes or attached structures; detached structures have corresponding setbacks¹⁹. Those park-development standards do not establish permission to occupy an RV on an individual private parcel²⁰.

1. Ask the Planning Department whether the parcel lies in a citizen-initiated zoning district and what standards apply there^6,11.
2. Confirm whether the project is exempt from the state building permit; non-exempt buildings require a state permit unless a certified local program has jurisdiction².
3. Apply to Ravalli County Environmental Health for the on-site wastewater-system permit before pouring a foundation; every owner of record must sign, and the application needs a legal property address^5,17.
4. If the wastewater system is within 300 feet of a delineated floodplain, obtain Planning's floodplain determination before the septic permit can issue^11,17.
5. Pay the wastewater fees before review and complete any required site evaluation, groundwater monitoring, non-degradation analysis and design work^17,18.
6. Arrange the wastewater-system inspection before covering the installation with fill⁵.

Settle wastewater feasibility before choosing the house site: only 1.1% of Ravalli County soils avoid severe limitations for a conventional drain field, and Environmental Health may require site evaluation or groundwater monitoring^8,17. Confirm district boundaries and land-division limits with Planning^7,11. Standard subdivision review applies when no exemption fits; the agricultural subdivision exemption requires exclusive agricultural use of the created parcel, with full exemption criteria and sanitation requirements still needing review⁷. Projects in the regulatory 100-year floodplain require a county floodplain application; ask Planning for the current project classification and fee^11,21,22. For a new well, Montana’s permit exception may cover use of 35 gpm or less and no more than 10 acre-feet annually; beginning in 2026, file a Notice of Intent with DNRC before using water under that exception²³. Ravalli County’s effective property-tax rate is about 0.5%, with a median annual bill of about $2,303⁸.