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

Sheridan County is not a certified local building-code jurisdiction, so areas without another certified local program fall under the Montana State Building Codes Bureau¹. Montana's state permit exemption covers farm and ranch buildings, private garages and storage buildings used by the owner rather than a business, and residential buildings containing fewer than five dwelling units unless they serve transient guests¹⁴. An ordinary single-family home for the owner's use therefore falls within the residential exemption, while a home intended for transient guests does not². Projects that do require a state permit are subject to state inspections, and the permit holder must notify the inspector when work is ready⁶. Montana's uniform state building code is enforced statewide even in places without a certified local program, so a permit exemption is not an exemption from the code itself⁶. The state-adopted International Building Code and International Residential Code are the 2024 editions, effective September 26, 2026, so projects starting now should be designed to those editions¹⁴.

For projects covered by Montana's state permit program, contact the Montana Building Codes Program, which issues permits and performs inspections⁶. For Growth Policy, subdivision and land-use questions, call Sheridan County Planning through the courthouse contact published on its official page³. Septic permits stay with the county: Sheridan County Environmental Health/Sanitarian handles approval before a residential septic system is installed and answers system questions, including for homes near town^5,15. Inside the City of Plentywood, zoning is set by the city under its own zoning regulations, but we could not open its ordinance, so ask the city about districts and standards⁴. Subdivision sanitation is reviewed by Montana DEQ for divisions under 20 acres and RV or mobile-home parks, and otherwise by DEQ or the authorized local Board of Health or Sanitarian^7,11. County-road approaches and other right-of-way encroachments go through Sheridan County Road & Bridge^16,17.

Sheridan County's Growth Policy is explicitly non-regulatory, but that statement alone does not establish whether a separate county zoning ordinance currently exists³. We could not confirm countywide zoning districts or numeric rules for minimum home size, minimum lot size, setbacks, lot coverage or building height; ask Sheridan County Planning about the exact parcel before relying on the absence of a published standard³. Parcels inside Plentywood fall under the city zoning regulations instead of the county Growth Policy⁴. Montana law allows a county with an adopted growth policy to adopt zoning through a separate process, so a growth policy and zoning ordinance are not the same thing¹⁸. Subdivision rules are confirmed: Sheridan County regulates land divisions, and a conditional agricultural exemption applies only to qualifying parcels dedicated to agricultural use and restricted against residential, commercial or industrial buildings requiring water or sewer¹¹.

Sheridan County Environmental Health/Sanitarian must approve a residential septic system before installation, and a local drainfield permit is required even when the lot already has a Certificate of Subdivision Approval from the state^5,7,15. Montana DEQ sets the state water-quality standards, and a local board of health may add rules that are no less strict than the state's⁸. DEQ itself reviews sanitation for divisions of land under 20 acres and for RV or mobile-home parks of any size, and the county's subdivision regulations name DEQ or the local Board of Health or Sanitarian as the reviewing authority^7,11. An onsite system discharging 5,000 gallons per day or more needs a Montana groundwater-pollution-control permit⁷. Only about 5% of Sheridan County soils lack severe limits for a conventional drain field, so obtain a site evaluation early and allow for an alternative design¹³. We could not confirm a general residential inspection schedule; ask the Sanitarian when applying¹⁵.

We could not confirm a countywide rule that allows or prohibits living in a single RV, tiny home or manufactured home on an ordinary private parcel in Sheridan County³. The county's non-regulatory Growth Policy does not answer occupancy, minimum-size or setback questions for a particular parcel³. A development with two or more recreational-vehicle spaces must go through county subdivision review before spaces are rented or leased, as a major subdivision at six or more spaces and a minor one at five or fewer, with spaces at least 15 feet apart and 25 feet from a public road right-of-way¹¹. Those RV-park standards do not resolve a single RV on private land¹¹. Developments with two or more manufactured-home spaces likewise require county subdivision approval before rental or lease¹¹. Before buying for any of these uses, ask Planning about land use and the Sanitarian about water and wastewater approval^3,15.

1. Ask Sheridan County Planning whether parcel-specific zoning, subdivision or dimensional restrictions apply³.

1. Confirm the water plan: groundwater at or below 35 gallons per minute and 10 acre-feet per year may use the permit exception, but a Notice of Intent (Form 602I) must be filed with DNRC before the water is used, and the driller files a well log within 60 days⁹. All surface-water uses and groundwater above either threshold need a water permit¹⁰.

1. Get local health approval and the drainfield permit before installing the septic system; subdivision review or the large-system state permit may also apply^7,8,15.

1. Ask the Montana Building Codes Program whether the proposed use falls outside the building-permit exemptions^2,6. An owner doing the plumbing personally in a personal residence that is neither speculative nor a rental does not need a state plumbing permit¹².

1. For development in a designated Special Flood Hazard Area, get an application from the local floodplain administrator before work; ask Planning to identify that official^3,19.

1. Obtain MDT approval for a state-highway approach. For work affecting a county road right-of-way, secure the county encroachment permit before starting and give Road & Bridge at least 24 hours' notice of commencement^16,20.

Water is the first thing to check here: annual precipitation is about 14.8 inches, and 19.2% of years bring severe drought¹³. Only about 5% of Sheridan County soils lack severe limits for a conventional drain field, so price the site evaluation and possible alternative design before closing¹³. Check flood status too: development in a designated Special Flood Hazard Area needs a permit, and Sheridan County restricts subdivision of floodway land for building or residential use^11,19. A subdivision with any part within 2,000 feet horizontally and 20 feet vertically of a live stream draining 25 square miles or more needs a flood-hazard evaluation by a licensed engineer, unless DNRC waives it in writing¹¹. A county-road encroachment permit carries a $35 administrative fee and requires at least $500,000 in single-occurrence liability insurance¹⁶. Typical property tax runs about 1.3% effectively, with a median bill near $1,436 a year, against a typical home value around $188,024¹³.