Bolthole Index

Big Horn County, Montana

Building permits, zoning and land rules in Big Horn County, Montana

63Index Score / 100
#28 of 56 in Montana

Unincorporated Big Horn County, Montana generally does not require a building permit for a single-family home, but septic and floodplain permits may still apply.123 Big Horn County's countywide zoning status could not be confirmed, so ask the County Commissioners about parcel-specific land-use limits before buying or building.45

At a glance

Building permit
Generally not required for a single-family home in an unincorporated area1
Zoning
Countywide status could not be confirmed; ask the County Commissioners45
Septic
Permit issued by Big Horn County Public Health's sanitarian2
Building inspections
State inspections apply when a project requires a state building permit6
RV or tiny-home living
Countywide private-land rules could not be confirmed; ask the County Commissioners45
Owner-builder
No distinct residential building exemption could be confirmed7
Floodplain
Development in a designated hazard area requires a local permit38

Who to call

Planning & zoning

Big Horn County Commissioners

First contact for unconfirmed county zoning, RV occupancy, tiny-home siting, setbacks and minimum-home-size questions

406-665-9700

121 W 3rd Room 301 Hardin, MT 59034

Septic permits

Big Horn County Environmental Health Department

Septic-system permit applications, site visits, final inspections and operating permits

406-665-8720

[email protected]

809 N CUSTER AVE HARDIN, MT 59034

Floodplain permits

Big Horn County Floodplain Administrator

Floodplain-status questions and local applications for development in designated flood hazard areas

(406) 665-9735

[email protected]

121 Third St. West Hardin, MT 59034

Roads & driveways

Big Horn County Roads, Junk Vehicle & Rural Fire

County-road questions, including whether proposed access needs county review

406-665-9860

803 N Center Avenue Hardin, MT 59034

Contact details are copied from each office’s official page and were checked against it on September 29, 2026.

Do you need a building permit in Big Horn County, Montana?

A single-family home in unincorporated Big Horn County generally does not require a residential building permit.1 Montana's state program exempts residential buildings containing fewer than five dwelling units when they do not serve transient guests, while covered construction still needs a state permit before work begins.9

The exemption does not settle every permit question. Separate electrical, plumbing or mechanical permits may apply, and projects that fall under state building-code jurisdiction follow the state's plan-review and inspection process.106 A certificate of occupancy is tied to construction under an applicable state or local building code rather than imposed universally on every structure.11

Who handles Big Horn County building and permit questions?

Big Horn County does not identify a general residential building department in the available county material, and we could not confirm a certified local building-code program for rural Big Horn County.1 Start with the Big Horn County Commissioners for parcel-specific county zoning, setback, RV, tiny-home or minimum-size questions that remain unconfirmed.45

For construction covered by Montana's state permit program, submit construction plans and a Building Permit/Plan Review Application to the Montana Building Codes Program.10 The state issues a permit after plan-review comments are resolved and required fees are paid, and separate trade permits may still be needed.10 State plan review averages three weeks, although timing varies with workload, project size and deficiencies.10

Does Big Horn County have zoning?

Big Horn County's countywide zoning status could not be confirmed from an authoritative Montana county source.4 Montana law allows a board of county commissioners that has adopted a growth policy to adopt zoning regulations, but that statewide authority does not prove that Big Horn County has adopted them.12

Ask the Big Horn County Commissioners whether the parcel lies under any county land-use regulation and whether setbacks, a minimum home size, RV occupancy or tiny-home placement are controlled by a subdivision approval or another parcel-specific restriction.5 Do not rely on search results for Big Horn County, Wyoming: that is a different county and its planning rules do not govern land in Montana.4

How do septic permits work in Big Horn County?

Big Horn County Public Health's sanitarian issues septic permits, and installation may not begin until the completed application and applicable fee are received and the permit to construct is issued.213 The county process calls for a site visit when necessary and requires a final inspection before the system is buried.13

Montana DEQ subdivision sanitation approval does not replace the local drainfield permit.14 Only 8.3% of mapped Big Horn County soils are rated without severe limitations for a conventional septic drain field, so make wastewater feasibility an early purchase contingency and expect the site evaluation to shape the design.15 Off-grid sanitation alternatives are not confirmed countywide; ask Environmental Health before choosing a nonstandard system.2

Can you live in an RV or tiny home in Big Horn County?

We could not confirm a countywide Big Horn County rule allowing full-time RV occupancy or a tiny home as a permanent dwelling on private land. Ask the Big Horn County Commissioners whether zoning, subdivision conditions, setbacks or minimum-home-size rules affect the specific parcel, and ask Environmental Health how the proposed occupancy must handle wastewater.452

A tiny home may fit the ordinary small-residential building-permit exemption only when the actual structure and use meet the exemption's conditions; septic requirements remain separate.19 Montana's camping limits for Fish, Wildlife & Parks public-use sites do not answer whether an owner may occupy an RV on private land.16

Building a home in Big Horn County: what should you do first?

  1. Ask the Big Horn County Commissioners whether county zoning, subdivision conditions, setbacks or other parcel-specific controls apply.45
  2. Confirm with the Montana Building Codes Program whether the proposed structure is exempt or needs state plans, permits and inspections.110
  3. Submit the septic application to Big Horn County Environmental Health and obtain the permit to construct before installation begins.213
  4. Ask the Floodplain Administrator whether the site is in a designated hazard area and obtain the local development application if it is.38
  5. Ask the county Roads office about local access; a new or modified approach to a state highway needs a state approach permit or right-of-way agreement.1718

What should you check before buying land in Big Horn County?

Start with wastewater feasibility because only 8.3% of mapped soils avoid severe conventional-drainfield limitations, and a local drainfield permit remains necessary even when Montana DEQ has approved subdivision sanitation.1514 Confirm water supply and utility-connection requirements directly because a general countywide connection rule could not be confirmed.2

Check floodplain status with the county administrator before planning fill, roads, excavation, a manufactured home or other development in a designated hazard area.38 Verify legal access with the Roads office, and use Montana's separate approval path when a driveway meets a state highway.1718 For carrying costs, the effective property-tax rate is about 1%, and the median annual tax bill is $1,482.1920

Watch-outs

  • Big Horn County, Wyoming search results describe a different county; do not use Wyoming planning rules for Montana land.4
  • Septic installation cannot begin until Big Horn County receives the application and fee and the sanitarian issues the permit to construct.13
  • A new or modified driveway approach to a Montana state highway requires an approach permit or right-of-way agreement.18

Sources

  1. Montana DLI Building Codes Program - Building Permit FAQ (2026 county census)
  2. Big Horn County Public Health Department - Septic Permitting (2026 county census)
  3. Stream Permitting (Montana statewide rule), quoted and re-checked
  4. (2026 county census)
  5. Big Horn County Commissioners (bighorncountymt.gov)
  6. Building Permits (Montana statewide rule), quoted and re-checked
  7. (2026 county census)
  8. Big Horn County Floodplain Administrator (dnrc.mt.gov)
  9. Building Permits (Montana statewide rule), quoted and re-checked
  10. Building Permits (Montana statewide rule), quoted and re-checked
  11. 50-60-107. Certificate of occupancy, MCA (Montana statewide rule), quoted and re-checked
  12. 76-2-201. County zoning authorized, MCA (Montana statewide rule), quoted and re-checked
  13. Big Horn County Environmental Health Department (bighorncountypublichealth.com)
  14. Engineering Infrastructure & Subdivisions (Montana statewide rule), quoted and re-checked
  15. Share of soils without severe limits for a conventional septic drain field (USDA SSURGO): Bolthole Index county data
  16. Public Use Rules and Regulations (Montana statewide rule), quoted and re-checked
  17. Big Horn County Roads, Junk Vehicle & Rural Fire (bighorncountymt.gov)
  18. Approach Manual for Landowners and Developers (Montana statewide rule), quoted and re-checked
  19. Effective property tax rate: Bolthole Index county data
  20. Median property tax bill: Bolthole Index county data

Written September 29, 2026 from the rules quoted below, each taken from an official source and re-checked by an independent reviewer. This is research, not legal advice: rules change, so confirm with the office before you buy or build.

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County locator

Big Horn County in Montana

63
County map
Big Horn County highlighted among the Montana counties · colored by Index score

How Big Horn County scores

Seclusion88100% ev.
Self-Sufficiency28100% ev.
Admin Boringness7168% ev.
Durability44100% ev.
Property Autonomy83100% ev.
Carry Cost8396% ev.

Evidence strength: 94%. This reports direct-source completeness and fallback use; it is separate from the score and is not a confidence interval. How it works →

$228kTypical home
1%Property tax
$649Land / acre
15.9"Annual rain
12.7% of yrsSevere drought
11.4 / yr (+9.4)Mid-century 100°F days
18.5 daysMid-century dry spell
1.11" (+4.6%)Mid-century 1-day rain
1.26×Wildfire change factor
100%Forward climate coverage
$2,129Home insurance / yr
1.5% / yrInsurance growth
0.9%Nonrenewal rate
single ZIP shrunk to state medianInsurance basis
178,356People within 2 hr
614Radius comparison (15 mi)
2.6People / sq mi
0.9%Federal land
63.7%Land at 15% slope or less
8.3%Septic soil without severe limits
257,460 acWorkable land screen
15.6%Wooded land
14.6 tonsBiomass / forest ac
45.4°FAvg temp

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Answers from the rulebook for Big Horn County

What the ordinances and state agencies actually say — one answer per question, each quoted from the official source and independently re-checked.

Montana rules that apply here

  • Building permitLimited

    Construction, remodeling, moving, alterations, additions, repairs, or changes of occupancy for buildings subject to Montana state building-code jurisdiction.

    • A state building permit is required before construction for certain types of new buildings and for certain alterations, additions, and repairs.
    • The state permit requirement does not apply to projects within the jurisdictional limits of a certified local government program; local requirements may apply there.
    • In the state's jurisdiction, state law exempts farm and ranch buildings; mining buildings on mining property; petroleum refineries and pulp and paper mills except office and shop buildings; residential buildings containing less than five dwelling units except when serving transient guests; and private garages and private storage buildings used for the owner's own use and not as part of a commercial enterprise or business.
    • Building permits must be issued on required projects before plumbing, mechanical, or electrical permits can be issued and before work authorized under those permits can start.
    “In Montana a state building permit is required prior to the start of construction for certain types of new buildings, and/or for alterations, additions, and repairs.”
  • Building code adoptedAdopted (with conditions)

    Montana's uniform state building code for residential and commercial buildings statewide.

    • The currently listed codes are amended and adopted through Administrative Rules of Montana Title 24, Chapter 301.
    • Cities, counties, and towns may enforce local building codes, all or in part, only through certified local building-code-enforcement programs.
    • State-owned agencies must be permitted through the Montana Department of Labor and Industry.
    • The listed 2021 International Building, Residential, and Existing Building Codes and related codes are effective June 11, 2022; the listed ASME boiler and pressure-vessel codes are effective November 6, 2021.

    International Building Code edition: 2021 · International Residential Code edition: 2021 · effective date for listed principal codes: 2022-06-11 (ASME boiler and pressure-vessel codes listed on the official page are effective 2021-11-06)

    “In addition, the program is responsible for adopting a uniform state building code, which is enforced statewide for residential and commercial buildings across Montana.”
  • InspectionsLimited

    Buildings and other projects requiring permits under Montana state building-code jurisdiction; certified local governments may perform inspections within their certified jurisdictional areas.

    • The Montana Building Codes Program performs inspections for projects requiring a permit under state jurisdiction.
    • The permit holder must notify the inspector when work is ready for inspection and provide access for required inspections.
    • Cities, counties, and towns may enforce local building codes and perform inspections only through certified local government programs; remaining areas fall under the state Building Codes Program.
    “The BC Program establishes and enforces statewide codes by issuing permits and performing inspections.”
  • Certificate of occupancyLimited

    Buildings constructed in accordance with the Montana state building code or a county, city, or town building code.

    • The certificate must certify that the building conforms to the applicable building regulations.
    • The statute addresses certificates for buildings constructed under the state or local building code; it does not establish a universal certificate requirement for every structure or every occupancy.
    “A certificate of occupancy for a building constructed in accordance with the provisions of the state building code or county, city, or town building code must certify that the building conforms to the requirements of the building regulations applicable to it.”
  • Who permits septicMixed (with conditions)

    Montana statewide sanitation and septic regulation, including subdivision sanitation review and drainfield permitting.

    • Montana DEQ administers subdivision sanitation review for covered divisions of land and related facilities.
    • The drainfield permit is administered by the local health department even when a Certificate of Subdivision Approval exists.
    “The DEQ Subdivision Program reviews divisions of land comprising less than 20 acres [...] This review is limited to sanitation facilities, including the water supply, sewage disposal, solid waste disposal, and storm drainage systems. [...] Yes, even thought you have a COSA, a drainfield permit is still required by the local health department.”
  • Septic permitRequired

    Installation of a drainfield in Montana, including property already covered by a Certificate of Subdivision Approval.

    • A Certificate of Subdivision Approval does not replace the drainfield permit.
    • The cited page identifies the local health department as the permitting authority.
    “Yes, even thought you have a COSA, a drainfield permit is still required by the local health department.”
  • Driveway accessLimited

    New or modified driveway approaches intersecting Montana state highways, and changes in use of property abutting a state highway or an existing approach.

    • A new or modified approach requires either an approach permit or a right-of-way agreement.
    • A change in property use or change in use of an existing approach requires a new approach permit.
    • The landowner is responsible for obtaining the new permit.
    • The application must be made to the appropriate MDT District Office.
    • A detailed site plan and Environmental Checklist Form are required.
    • The requirement concerns state highways; local roads may be administered by local governments.
    “ALL NEW OR MODIFIED APPROACHES REQUIRE EITHER AN APPROACH PERMIT OR A RIGHT-OF-WAY AGREEMENT.”
  • Building in a floodplainRequired

    New development within a designated Special Flood Hazard Area in Montana.

    • The applicant must check with the local floodplain administrator to determine whether an SFHA has been designated.
    • Covered development includes placement of fill, roads, bridges, culverts, transmission lines, irrigation facilities, storage of equipment or materials, excavation, new construction or development, placement or replacement of manufactured homes, and new construction, additions, or substantial improvements to residential and commercial buildings.
    • Permit applications are obtained from the local floodplain administrator.
    • Application fees and timelines are established by the local government and vary widely throughout the state.
    “Anyone planning new development within a designated Special Flood Hazard Areas (SFHA).”
  • Short-term rentalsLimited

    Short-term rentals operated in Montana.

    • A Property Manager license is required unless the operator qualifies for an exemption under MCA § 37-56-104 or MCA § 50-51.
    • Local land-use, lodging, tax, and public-accommodation requirements may also apply.

    application fee: 50 USD

    “Short Term Rentals: A Property Manager license is required for short term rentals unless an operator qualifies for an exemption”
  • Permit feesVariable (with conditions)

    State building permit and plan-review fees for state-administered building permits.

    • The building permit fee is calculated by the bureau under IBC Section 109.2 as modified by ARM 24.301.138.
    • A plan review fee is charged in addition to the building permit fee and equals 35 percent of the building permit fee.
    • Both fees must be paid before the building permit is issued.
    • Local governments certified to enforce the state building code may establish their own permit fees and valuation method.

    plan review fee: 35 percent of building permit fee

    “The plan review fee is 35 percent of the building permit fee as established in Table 109.2.”
  • Permit processPublished (with conditions)

    State-administered Montana building permits for covered non-exempt construction outside certified local-government jurisdictions.

    • A state permit applies to certain new buildings and alterations, additions, and repairs.
    • Projects within the jurisdictional limits of a certified local government program are excluded from the state permit program.
    • Construction plans and a Building Permit/Plan Review Application must be submitted for review and approval.
    • The permit is issued after plan-review comments are satisfactorily answered and fees are paid.
    • Separate electrical, plumbing, and mechanical permits may be required.
    • The permit holder must notify the inspector when work is ready and provide access for required inspections.

    average plan review time: three weeks (Actual timing depends on workload, project size, and deficiencies.)

    “To obtain a state building permit, submit construction plans and a Building Permit/Plan Review Application to the Building Codes Program for review and approval.”
  • Campground & park staysLimited

    Camping in Montana Fish, Wildlife & Parks public-use sites.

    • Camping is prohibited except in areas specifically designated or marked for camping.
    • A camping unit, vehicle, equipment, or personal items may not be left overnight without a person present.
    • Camping longer than 7 nights at one or more campsites in a public use area during any consecutive 30-day period is prohibited unless otherwise posted by the department.
    • Designated occupancy limits must not be exceeded.
    • Special-use-permit terms must be followed unless otherwise posted.
    • Campsites must be vacated by 1 p.m. on the day of departure; camping facilities must be vacated by 12 p.m. on the day of departure.

    maximum camping duration: <= 7 nights per consecutive 30-day period (unless otherwise posted by the department) · campsite departure time: 1 p.m. · camping-facility departure time: 12 p.m.

    “Unless otherwise posted by the department, within a public use site it is prohibited to: [...] camp at one or more campsites in a public use area for a period of longer than 7 nights during any consecutive 30-day period, beginning with the first night occupied unless otherwise posted by the department;”
  • county zoning authorityGeneral

    Montana boards of county commissioners adopting zoning regulations for all or parts of their jurisdictional areas, including unincorporated land.

    • The board of county commissioners must have adopted a growth policy pursuant to Montana Code Annotated chapter 1.
    • Zoning regulations must be adopted in accordance with Title 76, chapter 2.
    • The statute also contains a temporary provision for counties that adopted a master plan before October 1, 1999; that provision authorized adoption or revision only until October 1, 2006.
    “a board of county commissioners that has adopted a growth policy pursuant to chapter 1 is authorized to adopt zoning regulations”

Still unanswered

We looked and could not find an official answer yet. Silence is not permission — ask the county directly.

  • Owner-builder exemption — Owner-builder exemptions from applicable building requirements in Big Horn County.
  • Off-grid sanitation — Off-grid sanitation systems in Big Horn County.
  • Mandatory utility hookup — Water and sewer utility connection requirements in Big Horn County.
  • Agricultural exemption — Agricultural exemptions from county or state development permits in Big Horn County.

Each answer was extracted from an official source and independently re-checked against that source by a second reviewer. That is an evidence check, not legal advice. Rules change; confirm with the authority before you buy or build.

Living off-grid in Big Horn County, Montana

Is Big Horn County a good place to live off-grid or homestead?

Big Horn County scores 63/100 on the Bolthole Index, a solid county profile. Its strengths: deep seclusion — about 614 people within 15 miles and a stronger property-autonomy legal backdrop. Watch-outs: thin water margin (15.9″/yr rainfall).

Do you need a building permit in Big Horn County, Montana?

Big Horn County does not require a county building permit for a home in unincorporated areas. Onsite septic is permitted by Big Horn County Public Health Department (County Sanitarian), under MT DEQ rules. Rules change and cities within the county differ — always confirm with the county before you buy or build.

How much does land cost in Big Horn County, Montana?

Land in Big Horn County runs about $649 per acre, based on the latest county data.

What is the water situation in Big Horn County?

Big Horn County gets about 15.9" of rain a year, with severe drought in roughly 12.7% of years.

How remote is Big Horn County?

A typical private-land location has about 614 people within 15 miles and 282,345 within 100 miles. These radius catchments are the published fallback where road routing is unavailable.

Off-grid gear

Going off-grid in Big Horn County means bringing your own water and power. The kit we’d start with:

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How Big Horn compares in Montana

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