Building permits, zoning and land rules in Madison County, Montana

Madison County directs property owners to ask the Sanitarian whether a construction or demolition project requires the county's Construction/Demolition permit; the county source does not say that every project needs a general building permit¹. Madison County's construction/demolition permit is its own requirement, separate from the state building permit, and the county source does not say it covers every project¹. Construction/demolition fees vary by project size, and the application and payment go to the Sanitarian's Office^9,13.

Montana's adopted building codes apply statewide, but the state building permit is a separate requirement with exemptions^2,14. State law exempts farm and ranch buildings, most residential buildings with fewer than five dwelling units unless they serve transient guests, and owner-use private garages or storage buildings outside a business². The agricultural exemption is only from the state building permit, so it does not eliminate the county permit inquiry or septic rules². Owner-builders should know that Montana's contractor-registration exemption for an owner working on the owner's own property is not a blanket exemption from building, sanitation, zoning or county construction/demolition requirements¹⁰. State-permitted work requires inspections, and the permit holder must notify the inspector when work is ready².

Madison County's local construction/demolition application goes to the Madison County Sanitarian rather than a conventional county building department¹³. The Sanitarian is at 7 Placer Loop, Virginia City, MT 59755, can be reached at (406) 898-4338, and lists ksmart@madisoncountymt.gov as its office contact¹⁵.

For subdivision status, possible localized zoning, land-use review and floodplain questions, contact the Madison County Planning Office at 7 Placer Loop, Virginia City, MT 59755, (406) 898-4331, or planning@madisoncountymt.gov⁸. Montana's 2024 International Building Code took effect September 26, 2026, subject to permit exemptions and certified local programs¹⁴. For a non-exempt project in state jurisdiction, submit construction plans and the state application, resolve plan-review comments, pay the fees and arrange inspections².

A comprehensive countywide zoning system for unincorporated Madison County could not be confirmed³. County materials identify proposed citizen-initiated zoning districts in parts of the Raynolds Pass area, but do not establish countywide coverage or final dimensional standards⁶. Separately, inside the Airport Affected Areas around the Ennis Big Sky and Twin Bridges airports, a county Airport Affected Area permit must be obtained before certain uses, and one may be required depending on the proposed use, height or structural penetration⁴. Madison County also regulates subdivisions, so a general countywide answer does not establish what is allowed on a specific parcel⁷.

Ask the Planning Office to check the parcel for applicable local zoning, subdivision plat conditions, covenants, airport-area rules or other recorded development limits before choosing a house site⁸. Land created under the agricultural-use division exemption must remain exclusively agricultural; another use triggers subdivision review, and residential, commercial or industrial structures cannot be erected unless the covenant is revoked through that review⁷. For a subdivision without zoning that sets density or minimum lot size, those standards are established in consultation with local and state health authorities rather than by one numerical countywide minimum¹⁶. Construction near water is limited by the county's subdivision regulations: the minimum setback from the Madison River is 500 feet, from the Big Hole, Jefferson, Ruby, Beaverhead and South Boulder rivers at least 150 feet, and from other water bodies at least 100 feet, each measured from the ordinary high-water mark, with a variance needed for any change⁷. Minimum dwelling size, other setbacks, lot coverage and building height remain parcel-specific questions for Planning^3,8.

A permit is required for every septic or wastewater-treatment system installed in Madison County, and a Madison County Licensed Installer must perform the installation⁵. Applications go to the Madison County Sanitarian and require the county form, a site plan, applicable environmental documentation and a nonrefundable fee⁹. Published fees are $300 for a standard conventional system, $400 for an advanced alternative system, $600 for an experimental system and $200 for a replacement system⁹.

Madison County must inspect a regulated wastewater system before any portion is backfilled unless the department gives specific permission, and the applicant or installer must request the inspection at least 24 working hours before completion¹⁷. The department's response period is 10 working days for a complete standard application and 30 calendar days for specified multi-user, public subsurface or engineering-review systems⁹. Only 16.3% of county soils are rated without severe limitations for a conventional drain field, so settle wastewater feasibility early¹⁸.

Madison County's countywide rules for long-term RV occupancy, temporary camping on private land and tiny-home occupancy could not be confirmed³. Do not treat the absence of a confirmed countywide rule as permission: ask the Planning Office whether localized zoning, subdivision conditions or other parcel-specific restrictions apply^3,8.

The wastewater question is clearer than the occupancy question. A tiny home or occupied RV that relies on a new, repaired, replaced or altered wastewater treatment system falls within Madison County's local permit framework, subject to the regulation's stated exceptions⁹. Separately, Madison County's Buildings for Lease or Rent Regulations apply countywide to structures used for housing, including spaces where RVs or mobile homes are placed for rent; the first three or fewer such buildings on one tract need sanitation or health review when state law requires it, and further buildings need review and approval by the governing body¹⁹. Those rules do not name tiny homes specifically, so they matter mainly if you plan to rent a unit out¹⁹. The county materials also do not establish a complete rule for every off-grid sanitation alternative, so discuss the proposed toilet, wastewater and water setup with the Sanitarian before buying equipment or moving onto the parcel^5,15. A Montana rule limiting stays at state public-use sites does not answer whether residential RV use is allowed on private land²⁰.

1. Ask the Planning Office to confirm the parcel's subdivision status, any localized zoning and whether floodplain review is implicated^6,8,13.

1. Contact the Sanitarian to determine whether the work needs Madison County's construction/demolition permit and obtain the application and fee amount^1,21.

1. Establish wastewater feasibility, retain a Madison County Licensed Installer and submit the septic materials⁵.

1. Determine whether the structure is exempt from the state building permit; most private homes and farm or ranch buildings are exempt².

1. If you will do your own trade work, confirm the state homeowner exceptions: an owner who personally installs plumbing in a home for personal use needs no state plumbing permit, but not for speculative resale or rental property, and plumbing standards still apply¹¹; owner-performed wiring of the owner's home, garage and premises still requires a state homeowner's electrical permit and state inspection²².

1. For a non-exempt structure, submit plans and the state application, pay the fees and arrange inspections².

1. Schedule the septic inspection before backfilling the system¹⁷.

Start with legal buildability: confirm subdivision history, agricultural-use covenants, localized zoning and floodplain status with the Planning Office^3,7,8. Land divided under the agricultural-use exemption must remain exclusively agricultural; residential, commercial or industrial construction requires the covenant to be revoked through subdivision review⁷. New development in a designated Special Flood Hazard Area requires local floodplain review, with permit details set locally²³.

For a groundwater well using no more than 35 gallons per minute and 10 acre-feet per year, no permit application is required, but a Notice of Intent is required before use and well-log and completion filings follow development¹². Only 16.3% of county soils are rated without severe limits for a conventional septic drain field, and 41.2% of county land has a slope of 15% or less¹⁸. The effective property-tax rate is about 0.4%, with a median annual bill of about $1,800¹⁸.