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

An owner-occupied residence with fewer than five dwelling units in state jurisdiction is exempt from Montana's building permit unless it serves transient guests². Farm and ranch buildings and private garages or storage buildings used by the owner outside a business are also exempt from the state permit², and the state exemption does not remove county septic, well, floodplain or subdivision requirements². Montana has nevertheless adopted a uniform statewide building code, and the State Building Codes Bureau handles areas outside certified local programs, including Sanders County⁹. Covered construction, additions, alterations and repairs need the state permit before work starts and are subject to state inspections². In unincorporated Sanders County, buildings created for lease or rent have a separate county review path; some require sanitation review and a recorded certificate, while other rental buildings on one tract require governing-body approval⁵. Vacation and tourist homes are also licensed and inspected through Environmental Health³.

Sanders County Land Services is the first call for subdivision, Buildings for Lease or Rent, floodplain, airport-affected-area and road-encroachment matters⁴. For a project covered by Montana's building-permit rules, the State Building Codes Bureau issues permits and performs required inspections because Sanders County is not listed as a certified local building-code program^2,9. Sanders County Environmental Health handles well and wastewater permits and inspections^3,10. Environmental Health applications require the applicable information and fees, while the exact fees are set or changed by the county board rather than stated in the regulations¹¹. The Road Department supplies the appropriate encroachment paperwork for a driveway from a county road or Montana state highway⁸.

Unincorporated Sanders County has no adopted county zoning regulations¹. That means county zoning does not impose a minimum dwelling size, minimum lot size, general setback, lot-coverage limit or building-height limit there¹. It does not mean every parcel is unrestricted: subdivision, floodplain, airport, wastewater, well and private-covenant limits can still control a site^1,4. Buildings for lease or rent have their own standards, including a ten-foot property-line setback unless the governing body requires more and a fifty-foot height limit⁵. Mobile-home parks under those rules also have space-specific coverage limits⁵. Incorporated Thompson Falls, Plains and Hot Springs are outside the county's Buildings for Lease or Rent rules and may have their own local requirements⁵.

Sanders County requires a permit before installing, modifying, repairing, replacing or increasing use of a wastewater system unless a listed exception applies⁶. Environmental Health must inspect a permitted system before it is covered, and final approval is required to keep the permit valid⁶. A homeowner may install a standard-gravity system on the homeowner's own parcel after scoring at least ninety percent on the installer exam, but that route excludes ETA beds, sand mounds and advanced-treatment systems⁶. Only 4.5% of Sanders County soils lack severe limits for a conventional drain field, so make wastewater feasibility an early purchase contingency¹². A new well also needs a county permit before construction⁷. Structures generating wastewater must use the applicable public connection, compliant treatment system or approved toilet option, and a portable chemical toilet cannot be a permanent wastewater system for a structure⁶.

County zoning does not bar RV, tiny-home or manufactured-home occupancy in unincorporated Sanders County because the county has no zoning ordinance¹. Sanitation rules still apply: camping in one location for thirty days or more outside a licensed campground or RV park may require a compliant waste-disposal plan⁶. The permit exception for de minimis camping wastewater does not cover wastewater from an RV or another plumbed fixture⁶. An occupied tiny home must also have an approved wastewater system or another approved toilet facility, and a structure with piped water must meet the county's connection or treatment-system alternatives⁶. Rental use changes the answer: buildings created for lease or rent may need county review, and vacation or tourist homes are licensed and inspected^3,5. Ask Land Services about floodplain, airport and rental review, and ask Environmental Health to approve the sanitation plan before moving a dwelling onto the parcel^4,10. A tiny home used as housing falls under the county's rental-building review if it is offered for lease or rent in unincorporated Sanders County; incorporated Thompson Falls, Plains and Hot Springs are outside that county regulation⁵.

1. Ask Land Services whether the parcel triggers subdivision, floodplain, airport-affected-area or Buildings for Lease or Rent review⁴.

1. Determine whether the project is exempt from Montana's state building permit or needs state plan review, permits and inspections².

1. Apply to Environmental Health for the well and wastewater approvals; county applications require the applicable information and fees^6,7,11.

1. Use a licensed installer, or qualify to install your own standard-gravity septic system by passing the homeowner exam⁶.

1. Complete the county or state driveway-encroachment paperwork that matches the road, including the required site plan for county-road access⁸.

1. Arrange the required septic inspection before covering the system and obtain final approval⁶.

Start with wastewater feasibility because only 4.5% of Sanders County soils lack severe limits for a conventional drain field¹². Review terrain and clearing needs because only 23.6% of the county is at a slope of 15% or less and 75.3% is wooded¹². Confirm legal and physical access; a new county-road driveway requires encroachment paperwork, a site plan and county approval, while state-highway access uses the state process¹³. Ask Land Services whether floodplain, airport or subdivision rules affect the parcel, since the absence of zoning does not remove those reviews^1,4. Updated county subdivision regulations took effect October 1, 2026 and replaced the regulations adopted in 2020¹⁴. More than half of Sanders County—52.4%—is federal land, so verify boundaries and recorded access instead of assuming adjoining open ground belongs to the parcel¹².