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

A single-family residence in the part of Fergus County served by the State Building Codes Bureau is exempt from the state building permit¹. Farm and ranch buildings are also exempt from the state building permit, but that exemption does not remove septic, subdivision, floodplain, utility or other requirements¹. The state building codes for areas under the State Building Codes Bureau include the 2024 International Building and Residential Codes, effective September 26, 2026¹⁰. Nonexempt buildings and alterations may need a state permit, and permitted work requires inspections^1,11.

Fergus County separately requires a development permit before any construction². The county charges $50 for that permit and lists $500 when construction begins before it is obtained². An owner working on the owner's property may qualify for a construction-contractor registration exemption, but that exemption does not waive applicable building or trade permits and inspections⁸.

Lewistown has the certified local building-code program within city limits; other parts of Fergus County fall under the State Building Codes Bureau³. Start a rural project with the Fergus County Planning Office because it handles development permits, floodplain programs, addressing, mapping and land-use questions¹². The county development permit identifies property, road and floodplain limitations, assigns a physical address and supplies an encroachment permit when needed².

For a nonexempt project in state jurisdiction, submit construction plans and a Building Permit/Plan Review Application¹¹. The state issues the permit after written responses resolve plan-review comments and the fees are paid; required plumbing, mechanical or electrical work cannot begin before the building permit is issued¹¹. The permit holder must notify the inspector when work is ready and provide access¹¹.

Where Lewistown or the state handles building permits, septic permits for the parcel still come from Fergus County Environmental Health⁵.

We could not confirm a countywide zoning ordinance for Fergus County, so do not treat a rural parcel as unrestricted⁴. Local controls vary: the county describes City-County Planning Board jurisdiction in Lewistown and a surrounding county area, while Lewistown says its Planning Department handles zoning in the city and the surrounding area⁶. The Fergus County Planning Office is the first call for the governing jurisdiction because it handles land-use questions¹².

Ask Planning to identify the parcel's jurisdiction before relying on assumptions about RV occupancy, tiny homes, setbacks, minimum dwelling size, lot size, lot coverage or building height; published countywide answers could not be confirmed⁴. Montana law permits county zoning only after statutory prerequisites and allows zoning for all or part of a county jurisdictional area, so statewide authority alone does not establish a rule for a Fergus County parcel¹³.

Fergus County Environmental Health administers septic and wastewater matters and publishes a septic application and site-visit request, as-built materials, installer applications and site-evaluator applications⁵. A local drainfield permit remains required when a property already has a Certificate of Subdivision Approval⁷. The published new-system charge is $200 plus a $6 service fee for a certified installer, or $650 plus a $19.50 service fee for an owner or uncertified installer⁵.

Only about 4% of Fergus County soils are rated without severe limitations for a conventional drain field, so evaluate the site early¹⁴. Montana DEQ reviews sanitation for divisions of land smaller than 20 acres and reviews condominiums, recreational camping vehicle parks and mobile-home parks regardless of parcel size⁵. The complete county inspection sequence could not be confirmed; ask Environmental Health when site visits or inspections must occur before work is covered⁵.

We could not confirm a Fergus County rule that allows or prohibits long-term RV occupancy on private land⁴. We also could not confirm a separate tiny-home occupancy rule, a countywide minimum dwelling size or a countywide setback schedule⁴. Ask the Fergus County Planning Office about the exact parcel and proposed use before buying or moving a unit onsite; the office handles land-use issues¹².

Sanitation remains a separate question from land use: Fergus County Environmental Health administers septic matters, and a local drainfield permit remains required even when a Certificate of Subdivision Approval exists^5,7. A proposed recreational camping vehicle park or mobile-home park also enters Montana DEQ subdivision review regardless of parcel size⁷. Rules for camping at Montana Fish, Wildlife & Parks public-use sites do not answer whether someone may occupy an RV on private Fergus County land¹⁵.

1. Ask the Fergus County Planning Office to confirm the parcel's jurisdiction, land-use constraints, floodplain status, addressing and access needs¹².

1. Obtain the county development permit before construction; it identifies property, road or floodplain limitations, assigns the physical address and provides an encroachment permit when needed².

1. Have Fergus County Environmental Health evaluate the wastewater proposal and complete the septic application and site-visit process⁵.

1. Determine whether the structure is exempt from a state building permit or needs state plans, review, trade permits and inspections^1,11.

1. Before developing a qualifying permit-exception well, file the required Notice of Intent with DNRC; larger groundwater uses require a water permit⁹.

1. Contact Road and Bridge about county-road access, or MDT for a new or modified approach onto a state highway^16,17.

Start with buildability: have Planning identify property, road and floodplain limitations, and ask Environmental Health about wastewater feasibility^2,5. Only about 4% of county soils are rated without severe limits for a conventional drain field, while about 58.6% of the land has a slope of 15% or less¹⁴. Arrange parcel-level soil and water review before relying on those countywide figures^5,9.

Ask Road and Bridge about county-road access; a new or modified approach to a state highway needs a state approach permit or right-of-way agreement^16,17. Development in a designated Special Flood Hazard Area requires local review, and the county's published floodplain review fee is $500^2,18. The median property-tax bill is about $1,709 per year, with an effective rate near 0.8%¹⁴.