Bolthole Index

Custer County, Montana

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

49Index Score / 100
#43 of 56 in Montana

Unincorporated Custer County, Montana requires a zoning conformance permit before construction or expansion, except for a qualifying accessory structure under 100 square feet1. Montana separately exempts many small residential buildings from the state building-permit program, but county zoning approval still applies23. Septic permits come from Custer County Environmental Health4. Miles City and Ismay sit outside the county zoning rules5.

At a glance

Building permit
County zoning conformance permit required before construction or expansion in county zoning districts1
Small accessory structure
No county zoning conformance permit below 100 square feet if the structure meets the accessory definition and district standards1
Zoning
County zoning covers all of Custer County outside Miles City and Ismay, which have separate municipal rules56
Septic
Permit from County Environmental Health required to build, alter, expand or replace a system; final inspection before use478
RV or tiny-home living
Private occupancy is not fully confirmed; RV parks are conditional uses in AG-1 and C-19
Manufactured home
Allowed in R-1, R-2 and R-3 if it meets the county definition and foundation rules10
County-road driveway
$50 encroachment permit required for a new, expanded, altered or relocated approach1112
Floodplain development
Floodplain permit required in the Regulated Flood Hazard Area; county Zoning Administrator enforces the floodplain rules1314
Owner-builder
Owners may work on their own property without a Montana contractor license, but permits still apply15

Who to call

Planning & zoning

Custer County Zoning Administrator

County zoning conformance, zoning map and land-use questions for unincorporated Custer County

1010 Main Street, Ste. 2, Miles City, Montana, 59301

Health department

Custer County Environmental Health

Onsite wastewater, Sanitarian services and Montana DEQ liaison work in Custer County

Floodplain permits

Custer County Floodplain Development

Floodplain development applications and local floodplain documents

Roads & driveways

Custer County Road Department

County roads, bridges and encroachment permits for driveway or private-road approaches

(406) 232-1970

5125 Valley Drive East Miles City, Montana 59301

Contact details are copied from each office’s official page and were checked against it on October 9, 2026.

Off-grid gear

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

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Do you need a building permit in Custer County, Montana?

Yes, in the land-use sense: before constructing or expanding a structure in an unincorporated Custer County zoning district, the owner must obtain a zoning conformance permit1. A qualifying accessory structure under 100 square feet is exempt if it meets the accessory-structure definition and district development standards1. Montana also has a uniform state building code, enforced by the state where there is no certified local program16. The state program exempts farm and ranch buildings, qualifying private garages and storage buildings, and residential buildings with fewer than five dwelling units unless they serve transient guests2. A home can therefore be exempt from a state structural building permit while still requiring county zoning conformance approval23. Montana's contractor-licensing exemption lets an owner work on the owner's own property, but it does not itself exempt a project from building, electrical, plumbing, mechanical or inspection requirements15. We could not confirm a county owner-builder exemption from zoning approval or a certificate-of-occupancy rule; ask the Zoning Administrator.

Who issues Custer County building and land-use permits?

The Custer County Zoning Administrator is the first stop for construction on unincorporated land because county zoning conformance approval comes before construction or expansion3. The official zoning map controls a property's current county zoning status and is kept by the Zoning Administrator and County Clerk and Recorder1718. Reach the Zoning Administrator at 1010 Main Street, Ste. 2, Miles City, Montana, 5930119. If a nonexempt project falls under Montana's state building-code jurisdiction, the state process requires plans and an application, then plan approval and fee payment before permit issuance20. State-covered work may also need electrical, plumbing and mechanical permits20. Custer County's published county process is partial, so ask the Zoning Administrator which county forms accompany the conformance application3.

Does Custer County, Montana have zoning?

Yes. County zoning divides all of Custer County outside Miles City and the Town of Ismay into use districts5. Miles City and Ismay are outside the county regulations and may have their own municipal rules6. Dimensional rules depend on the district: R-2, for example, has a 5,500-square-foot minimum lot for a single-family residence, 15-foot front and 5-foot side setbacks, 35% lot coverage, and a 35-foot height limit21222324. Other districts differ, so use the official zoning map rather than assuming those figures apply everywhere17. Montana law also requires county zoning to allow at least one accessory dwelling unit by right on a parcel containing a single-family home, subject to building, fire, sanitation and other health-and-safety rules25. The county rules do not confirm a general minimum floor area for site-built homes or a specific tiny-home category; ask the Zoning Administrator how the proposed dwelling is classified.

How do septic permits work in Custer County?

Custer County Environmental Health, with its Sanitarian and Montana DEQ liaison services, administers onsite wastewater rules for the whole county826. A valid permit is required to construct, alter or increase the load on a system, and replacement systems need one too; no permit is needed where sewage goes to an approved public system4. A permit not yet used for construction stays valid for two years4. Owner-installed systems may not be backfilled until inspected and approved, and a new system may not be used before final inspection and approval7. Off-grid options are narrow: sealed pit privies only where there is no piped water, and holding tanks only for seasonal use under distance and testing conditions27. Montana also requires a local drainfield permit even when a property has a Certificate of Subdivision Approval, and parcels created by subdivision may fall under state DEQ review2829. Only 11.6% of Custer County soils are rated without severe limitations for a conventional drain field, so evaluate the site before choosing a house location30.

Can you live in an RV or tiny home in Custer County?

Custer County's rules define an RV park as land used for occupied recreational vehicles or tents serving as temporary living quarters for 180 days or less, and RV parks are conditional uses in AG-1 and C-19. That rule does not settle long-term occupancy of one RV on a private parcel, so ask the Zoning Administrator about the parcel and proposal before moving in. Tiny-home occupancy is also not specifically confirmed; a tiny home treated as a structure still needs zoning conformance approval before construction or expansion1. Manufactured homes are expressly allowed as single-family homes in R-1, R-2 and R-3 when placed on a permanent foundation, but the county definition also requires factory construction on or after January 1, 1990, at least 1,000 square feet, a pitched roof, customary siding and applicable HUD compliance10. Environmental Health should approve the wastewater plan separately8.

Building a home in Custer County: the steps in order

  1. Ask the Zoning Administrator to confirm the district, dimensional standards and whether the home is permitted outright or needs conditional-use approval173.
  1. Apply for zoning conformance approval before construction or expansion1.
  1. Take the site plan to Custer County Environmental Health and obtain the septic permit before installation; keep the system uncovered until it is inspected4728.
  1. Check the flood map; inside the Regulated Flood Hazard Area, a floodplain permit application needs a signed application, review fee, scaled plans and elevations, and the Floodplain Administrator decides a complete application within 60 days1331.
  1. Obtain the county encroachment permit before creating, expanding, altering or relocating an approach in a county right-of-way; the listed minimum fee is $501112. A state-highway approach instead goes through the appropriate Montana Department of Transportation district office32.
  1. Confirm whether state building, electrical, plumbing or mechanical permits apply before work starts20.

What should you check before buying land in Custer County?

Start with the official zoning map, lot dimensions and intended use because district-specific minimum lots, setbacks, coverage and height limits can change what fits333435. If the sale divides land, Custer County's subdivision rules apply within its jurisdiction, and some proposals near or partly inside a municipality require municipal review or approval too36. Investigate wastewater before fixing the building site because only 11.6% of county soils are rated without severe limits for a conventional drain field30. For a new small groundwater development, Montana may allow a permit exception, but a Notice of Intent to DNRC is required before use beginning in 202637. We could not confirm a county private-well permit rule, so ask Environmental Health about wells before drilling. Check flood status and legal access, including county or state approach approval as applicable311132. Custer County averages 14.5 inches of precipitation annually, so verify a dependable water source38.

Watch-outs

  • A Montana state permit exemption does not erase Custer County's zoning conformance requirement for construction in county zoning districts21.
  • The county's 180-day definition describes temporary living quarters in an RV park; it does not confirm that a private parcel may be occupied by one RV for that period9.
  • Only 11.6% of Custer County soils are rated without severe limitations for a conventional drain field, so resolve septic feasibility before committing to a building site30.
  • Floodplain permits come before zoning conformance approval for non-residential structures in a designated floodplain area, and the county Zoning Administrator enforces the floodplain regulations14.

Sources

  1. Custer County Zoning Regulations, Resolution #2016-31, quoted and re-checked
  2. Building Permits (Montana statewide rule), quoted and re-checked
  3. Custer County Zoning Regulations, Resolution #2016-31, quoted and re-checked
  4. County’s Onsite Waste Water Rules, quoted and re-checked
  5. Custer County Zoning Regulations, Resolution #2016-31, quoted and re-checked
  6. Custer County Zoning Regulations, Resolution #2016-31, quoted and re-checked
  7. County’s Onsite Waste Water Rules, quoted and re-checked
  8. Environmental Health, quoted and re-checked
  9. Custer County Zoning Regulations, Resolution #2016-31, quoted and re-checked
  10. Custer County Zoning Regulations, Resolution #2016-31, quoted and re-checked
  11. Road & Bridge, quoted and re-checked
  12. Road & Bridge, quoted and re-checked
  13. Custer County Floodplain Regulations, quoted and re-checked
  14. Custer County Zoning Regulations, Resolution #2016-31, quoted and re-checked
  15. Montana Code Annotated, Title 37, Chapter 45, Construction Contractors (Montana statewide rule), quoted and re-checked
  16. Montana Building Codes Program, quoted and re-checked
  17. Custer County Zoning Regulations, Resolution #2016-31, quoted and re-checked
  18. Custer County Zoning Regulations, Resolution #2016-31, quoted and re-checked
  19. Custer County Zoning Administrator (custercountymt.gov)
  20. Building Permits (Montana statewide rule), quoted and re-checked
  21. Custer County Zoning Regulations, Resolution #2016-31, quoted and re-checked
  22. Custer County Zoning Regulations, Resolution #2016-31, quoted and re-checked
  23. Custer County Zoning Regulations, Resolution #2016-31, quoted and re-checked
  24. Custer County Zoning Regulations, Resolution #2016-31, quoted and re-checked
  25. 76-2-215. Accessory dwelling units -- regulations -- restrictions, MCA (Montana statewide rule), quoted and re-checked
  26. Custer County Environmental Health (custercountymt.gov)
  27. County’s Onsite Waste Water Rules, quoted and re-checked
  28. Engineering Infrastructure & Subdivisions (Montana statewide rule), quoted and re-checked
  29. Engineering Infrastructure & Subdivisions (Montana statewide rule), quoted and re-checked
  30. Share of soils USDA rates "not limited" for a conventional septic drain field (SSURGO). A strict rating: the median county is about 6% and a tenth of counties are 0%, so a low figure means most lots need a site evaluation or an engineered system, not that septic is impossible. Cite it only with that caveat: Bolthole Index county data
  31. Stream Permitting (Montana statewide rule), quoted and re-checked
  32. Approach Manual for Landowners and Developers (Montana statewide rule), quoted and re-checked
  33. Custer County Zoning Regulations, Resolution #2016-31, quoted and re-checked
  34. Custer County Zoning Regulations, Resolution #2016-31, quoted and re-checked
  35. Custer County Zoning Regulations, Resolution #2016-31, quoted and re-checked
  36. Subdivision Regulations of Custer County, quoted and re-checked
  37. Exempt Well Updates and Information (Montana statewide rule), quoted and re-checked
  38. Annual precipitation: Bolthole Index county data

Written October 9, 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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Compared with neighboring counties

Unlike 5 of its 6 neighbors, Custer County requires a building permit only in limited cases.

RuleCuster CountyPrairie CountyFallon CountyPowder River CountyRosebud CountyCarter CountyDawson County
Building permitLimitedNot requiredNot requiredNot requiredNot requiredNot requiredLimited
County zoningYesNoNoNoNoNoYes
Septic permitsCounty Env. HealthCounty SanitarianCounty SanitationCounty SanitarianCounty SanitarianCounty SanitarianCounty Sanitarian

County locator

Custer County in Montana

49
County map
Custer County highlighted among the Montana counties · colored by Index score

How Custer County scores

Seclusion90100% ev.
Self-Sufficiency18100% ev.
Admin Boringness5590% ev.
Durability42100% ev.
Property Autonomy83100% ev.
Carry Cost8496% ev.

Evidence strength: 98%. This reports direct-source completeness and fallback use; it is separate from the score and is not a confidence interval. How it works →

$254kTypical home
1.1%Property tax
$1,017Land / acre
14.5"Annual rain
11.4% of yrsSevere drought
16.8 / yr (+12.3)Mid-century 100°F days
21.7 daysMid-century dry spell
1.07" (+5.2%)Mid-century 1-day rain
1.26×Wildfire change factor
100%Forward climate coverage
$2,086Home insurance / yr
-1.1% / yrInsurance growth
0.42%Nonrenewal rate
single ZIP shrunk to state medianInsurance basis
2,881People within 2 hr
216Radius comparison (15 mi)
3.2People / sq mi
16.7%Federal land
61.7%Land at 15% slope or less
11.6%Soils rated "not limited" for septic (strict USDA rating)
265,176 acWorkable land screen
3.6%Wooded land
10.1 tonsBiomass / forest ac
45.3°FAvg temp

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Cities and towns in Custer County

Inside a city or town, that city usually issues building permits and sets zoning; the county’s rules above cover unincorporated land. Septic, wells and floodplain rules usually stay with the county or state everywhere.

Not yet researched: Town of Ismay

Answers from the rulebook for Custer County

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

Custer County rules

  • Building permitLimited

    Construction or expansion of structures in county zoning districts in unincorporated Custer County.

    • A zoning conformance permit is required before construction or expansion.
    • No county zoning conformance permit is required for an accessory structure under 100 square feet if it meets the accessory-structure definition and district development standards.
    • Montana state law separately exempts residential buildings containing fewer than five dwelling units from state building permits, except when serving transient guests.
    • Municipal requirements may differ in Miles City and Ismay.

    accessory structure threshold: < 100 square feet (Must meet the accessory-structure definition and applicable district development standards.)

    “Prior to construction or expansion of a structure in any zoning district, a landowner shall obtain a zoning conformance permit from the Zoning Administrator to assure compliance with the zoning regulations.”
    One more reviewed finding on this topic
    • Limited — Construction or expansion of structures in county zoning districts.
      “Prior to construction or expansion of a structure in any zoning district, a landowner shall obtain a zoning conformance permit”
  • County-wide zoningPresent (with conditions)

    County zoning in unincorporated Custer County, excluding Miles City and Ismay.

    • Miles City and the Town of Ismay are excluded from the county zoning district system.
    • Structures and land uses must conform to the applicable district regulations and may require conditional-use approval.
    “For the purpose as described in Section 1, the entirety of Custer County exclusive of the municipalities of Miles City and the Town of Ismay is hereby divided into the following use classification districts:”
    One more reviewed finding on this topic
    • Present — County zoning in all Custer County territory outside Miles City and Ismay.
      “For the purpose as described in Section 1, the entirety of Custer County exclusive of the municipalities of Miles City and the Town of Ismay is hereby divided into the following use classification districts:”
  • Local zoningVaries (with conditions)

    Aggregate local zoning conclusion: county zoning applies in unincorporated areas, while incorporated Miles City and Ismay are excluded from the county regulations and may have separate municipal rules.

    • This is an aggregate conclusion and does not claim that the county administers municipal ordinances.
    • The county zoning regulations exclude Miles City and Ismay.
    “the entirety of Custer County exclusive of the municipalities of Miles City and the Town of Ismay”
    One more reviewed finding on this topic
    • Present (with conditions) — County zoning in unincorporated Custer County.
      “For the purpose as described in Section 1, the entirety of Custer County exclusive of the municipalities of Miles City and the Town of Ismay is hereby divided into the following use classification districts:”
  • Zoning districtsPublished (with conditions)

    Custer County zoning districts and their mapped extent.

    • The county land-use page publishes links to the zoning regulations and zoning map.
    • The 2026 update notice states that zoning districts and the extent of zoned areas are not being added or removed as part of that update.
    “The official zoning map, including any amendments made pursuant to these regulations, shall be maintained by and available at the Zoning Administrator’s Office and is also available on-line at the County’s website.”
    2 more reviewed findings on this topic
    • Published (with conditions) — Published county zoning districts and map for unincorporated Custer County.
      “The official zoning map shall be the final authority as to the current zoning status of properties, buildings and other structures in the county’s jurisdiction and shall be on file with the County Clerk and Recorder’s Office.”
    • Published — County zoning districts outside Miles City and Ismay.
      “The official zoning map, including any amendments made pursuant to these regulations, shall be maintained by and available at the Zoning Administrator’s Office and is also available on-line at the County’s website.”
  • Minimum lot sizeDistrict specific (with conditions)

    Residential zoning districts in unincorporated Custer County.

    • Requirements vary by zoning district and dwelling type.

    R-1 single-family minimum lot area: 5500 sq ft · R-1 duplex minimum lot area: 5500 sq ft · R-1 3-plex minimum lot area: 7200 sq ft · R-1 4-plex minimum lot area: 8900 sq ft · R-2 single-family minimum lot area: 5500 sq ft · R-2 8-plex minimum lot area: 15700 sq ft · R-3 minimum lot area: 6000 sq ft (The section separately lists dwelling-type minimum lot areas.)

    “1. Minimum Lot Area (sq ft): 6,000 2. Minimum Lot Area: a. 5,500 - single-family residence b. 5,500 - duplex;”
    2 more reviewed findings on this topic
  • SetbacksDistrict specific (with conditions)

    Building setbacks in unincorporated Custer County zoning districts.

    • Requirements vary by zoning district.
    • Commercial buildings adjoining residential districts must maintain applicable residential setbacks along the common boundary.

    R-1 front setback: 25 ft · R-1 side setback: 5 ft · R-1 rear setback: 20 ft · R-1 side-corner setback: 15 ft · R-2 front setback: 15 ft · R-2 side setback: 5 ft · R-2 rear setback: 20 ft · R-3 front setback: 15 ft · R-3 side setback: 5 ft · R-3 rear setback: 10 ft

    “3. Minimum Setbacks (ft): a. Front Yard - 15 b. Side Yard - 5 c. Rear Yard - 20 d. Side Corner - 15 e. Attached Garage (Front/Side Corner) - 20”
    One more reviewed finding on this topic
    • Specified — Residential zoning districts covered by the county property-development standards.
      “3. Minimum Setbacks (ft): Front Yard - 25 Side Yard - 5 Rear Yard - 20 .Side Corner- 15 Attached Garage (Front/Side Corner) - 15”
  • Lot coverageDistrict specific (with conditions)

    Lot coverage in county zoning districts.

    • Requirements vary by district.
    • R-2 permits 35 percent lot coverage.

    R-2 permitted lot coverage: 35 percent

    “5. Permitted Lot Coverage: 35 % 6. Parking - At least two (2) off-street parking space for each dwelling unit within the building or buildings.”
  • Building heightDistrict specific (with conditions)

    Maximum building heights in unincorporated Custer County zoning districts.

    • R-1, R-2, and R-3 residential maximum height is 35 feet.
    • C-1 commercial height may not exceed the limits of existing county fire-department equipment.

    R-1 maximum building height: 35 ft · R-2 maximum building height: 35 ft · R-3 maximum building height: 35 ft · C-1 maximum building height: limits of existing fire department equipment

    “4. Maximum Building Height (ft): Height is not to exceed the limits of existing fire department equipment in the County.”
    One more reviewed finding on this topic
  • Camping on your landLimited

    Temporary recreational camping and occupied recreational vehicles in unincorporated Custer County zoning districts.

    • A campground or recreational vehicle park is listed as a conditional use in AG-1.
    • A campground/RV park is listed as a conditional use in C-1.
    • The county defines temporary recreational-vehicle living quarters as 180 days or less.
    • Conditional uses require the applicable conditional-use process and standards.

    temporary camping period: <= 180 days or less (The source defines recreational vehicle parks as temporary living quarters for recreational camping or travel purposes.)

    “Recreational Vehicle Park. Any lot, tract or parcel of land used or offered for use in whole or in part with or without charge for the parking of occupied recreational vehicles, tents or similar devices used for temporary (i.e. 180 days or less) living quarters for recreational camping or travel purposes.”
  • Manufactured homesAllowed (with conditions)

    Manufactured-home single-family occupancy in the county's R-1, R-2, and R-3 residential districts.

    • The home must be placed on a permanent foundation.
    • The county definition requires construction off-site in a factory on or after January 1, 1990.
    • The county definition requires at least 1,000 square feet, a pitched roof, customary site-built-home siding, and compliance with applicable HUD standards.
    • A zoning conformance permit is required before construction or expansion unless the accessory-structure exception applies.

    minimum floor area: >= 1000 sq ft · manufacturing date: >= January 1, 1990

    “Manufactured Home. A single-family dwelling, built off-site in a factory on or after January 1, 1990, that is placed on a permanent foundation, is at least 1,000 square feet in size, has a pitched roof and siding materials that are customarily used on site-built homes, and is in compliance with the applicable prevailing standards of the United States Department of Housing and Urban Development at the time of its production.”
    3 more reviewed findings on this topic
    • Limited — Manufactured-home residential occupancy in county zoning districts.
      “Dwelling: manufactured home placed on a permanent foundation”
    • Allowed — A manufactured home placed on a permanent foundation in the county R-1 Residential Single Family district.
      “Permitted Uses 1. Accessory Uses 2. Hobby agriculture and horticulture 3. Dwelling – detached single family 4. Dwelling: manufactured home placed on a permanent foundation”
    • Allowed (with conditions) — A manufactured home on a permanent foundation in the county residential zoning district whose permitted uses include that use.
      “3.3 R-1 Residential [...] Permitted Uses [...] 4. Dwelling: manufactured home placed on a permanent foundation”
  • Who permits septicCounty

    On-site wastewater administration in Custer County.

    • State rules and state agency review may apply, including for subdivision-created parcels under the Montana Sanitation in Subdivision Act.
    • The more stringent state or federal rule applies if there is a conflict.
    “These regulations apply to all areas of the County’s. [...] The authority, rules, and regulations set forth herein shall not apply to those parcels created by subdivision when said parcels fall under the authority of a State of Montana Agency pursuant to the Montana Sanitation in Subdivision Act.”
    One more reviewed finding on this topic
    • County (with conditions) — Onsite wastewater administration in Custer County.
      “The Environmental Health department in Custer County encompasses Sanitarian, DEQ Liaison services at this time.”
  • Septic permitLimited

    New, altered, expanded, replacement, or load-increased on-site wastewater systems in Custer County.

    • A valid permit is required for construction, alteration, or load increases.
    • A permit is not required when sewage is disposed of through an approved public system.
    • Repairs may be made without a permit, including replacement of a septic tank, a collapsed or broken sewer line, or removal of a blockage.
    • Replacement systems require a valid permit; permits are valid for two years if construction has not begun.

    permit validity: 2 years (If construction has not begun, the applicant must reapply under current regulations.)

    “It is a violation of this regulation to construct, alter or make load increases to any on-site wastewater treatment system without compliance with the provisions of these regulations and the possession of a valid permit issued under these regulations.”
  • Septic inspectionRequired

    Onsite wastewater systems installed by certified installers or owners.

    • The CSO may allow self-inspection for certified installers.
    • Certified installers must give 48 hours' notice.
    • Owner-installed systems may not be backfilled until inspected and approved or authorized for self-inspection.
    • A new system may not be used before final CSO inspection and approval.
    • Required corrections must be completed and inspected before final approval.

    certified-installer notice: 48 hours · owner-installed inspection deadline: <= 6 working days (After notice of completion.) · self-inspection form deadline: 10 days (When self-inspection is authorized.)

    “until it has been inspected and approved”
  • Off-grid sanitationLimited

    Non-standard on-site sanitation systems in Custer County.

    • Sealed pit privies may be approved only where the facility does not have a piped water supply.
    • Holding tanks may be approved only for seasonal use and subject to distance, flotation, waterproofing, annual testing, pumping, and public-sewer-availability conditions.
    • All applicable county and state wastewater standards remain applicable.

    holding-tank setback from surface water or 100-year flood elevation: >= 50 feet horizontally (Holding tanks also must satisfy the other stated conditions.)

    “Sealed pit privies may only be approved if the facility to be served does not have a piped water supply. [...] Holding Tank systems may be approved if: (1) The facility to be served is for seasonal use only; (2) The holding tank system is located at least 50 feet horizontally from any lake, stream, irrigation ditch or surface water body, or the 100-year flood elevation of any watercourse;”
  • Subdividing landRegulated (with conditions)

    Subdivision of land within Custer County's jurisdictional area.

    • Within one mile of a third-class city or town, two miles of a second-class city, or three miles of a first-class city, the preliminary plat must be submitted to the city or town for review and comment.
    • If a proposed subdivision lies partly within an incorporated city or town, both governing bodies must approve it.
    • More restrictive applicable regulations control.
    “These regulations govern the subdivision of land within the jurisdictional area of the governing body of Custer County.”
    One more reviewed finding on this topic
    • Regulated (with conditions) — Subdivision of land within the jurisdictional area of the Custer County governing body.
      “The county commission of a county is the “governing body” for purposes of reviewing subdivisions located in unincorporated areas of the county. If a proposed subdivision will overlap the corporate boundaries of a municipality, the subdivision must be reviewed and approved, conditionally approved, or denied by both governing bodies”
  • Driveway accessRequired

    New construction, expanded use, alteration, or relocation of a driveway or private-road approach involving county right-of-way.

    • An encroachment permit is required before covered work is performed.
    • The minimum listed fee is $50 per approach.
    • The county may require a performance bond.
    • A 10 percent penalty applies to work performed without first obtaining an encroachment permit.

    minimum permit fee: 50 USD each (Driveway or private-road approach.) · unpermitted-work penalty: 10 percent of project permit cost (Assessed for work without first obtaining an encroachment permit.)

    “Driveway or Private Road Approach: New construction, expanded use, alteration of, or relocation of an existing approach. $50.00 each [...] A penalty of ten percent (10%) of the projects’ permit cost will be assessed to any individual or contractor who performs work without first obtaining an encroachment permit from Custer County.”
  • Building in a floodplainLimited

    Development, substantial improvements, alterations, and artificial obstructions in regulated flood-hazard areas administered under the county floodplain regulations.

    • A floodplain permit application requires a completed and signed application, review fee, scaled plans, elevations, and other applicable federal or state permits.
    • The Floodplain Administrator approves, conditionally approves, or denies a correct and complete application within 60 days unless otherwise specified.
    • A permit becomes valid when all other necessary federal or state permits are in place.
    • The reviewed zoning regulation states the county floodplain regulations control within Custer County outside the jurisdictional boundary of the City of Miles City and the Town of Ismay.

    application decision period: 60 days (Measured from receipt of a correct and complete application.) · floodway base-flood-elevation increase threshold: > 0 feet (Approval requires alteration approval if the increase is more than 0.00 feet.) · regulated flood-hazard-area base-flood-elevation increase threshold: > 0.5 feet (Applies where there is no floodway and requires alteration approval.)

    “A Floodplain permit is required for a person to establish, alter or substantially improve an artificial obstruction, nonconforming use or development within the Regulated Flood Hazard Area;”
    One more reviewed finding on this topic
    • Limited — Non-residential uses or structures in designated floodplain areas outside Miles City and Ismay.
      “A conformance permit shall not be issued for any non-residential use or structure within a designated floodplain area until all applicable floodplain permits have been issued.”
  • Permit feesPublished (with conditions)

    Published county zoning, planning, road-approach, utility-right-of-way, and floodplain-related fees.

    • Fees vary by permit type and department.
    • The road page states its encroachment fee schedule is effective July 1, 2002.
    • The wastewater regulations state that county Board of Health fees apply, but the reviewed source did not provide a current fee amount.

    new or modified driveway/private-road approach fee: 50 USD each (New construction, expanded use, alteration, or relocation of an existing approach.) · utility service connection in right of way: 50 USD each (Utility service connections to existing facilities in right of way.)

    “Driveway or Private Road Approach: New construction, expanded use, alteration of, or relocation of an existing approach. $50.00 each [...] Utility service connections to existing facilities in right of way $50.00 each”
  • Permit processPartial

    County zoning-conformance permitting and related land-use processes.

    • A zoning conformance permit is required before construction or expansion of a structure in a zoning district.
    • The county land-use page publishes zoning, planning, subdivision, and floodplain forms and documents.
    • Conditional uses require a separate conditional-use process.
    “Prior to construction or expansion of a structure in any zoning district, a landowner shall obtain a zoning conformance permit”
    One more reviewed finding on this topic
    • Published (with conditions) — County zoning conformance and conditional-use permitting in unincorporated Custer County.
      “Prior to construction or expansion of a structure in any zoning district, a landowner shall obtain a zoning conformance permit from the Zoning Administrator to assure compliance with the zoning regulations.”

Montana rules that apply here

  • Owner-builder exemptionAvailable

    An owner working on the owner's property, or an owner contracting for work performed by a registered construction contractor, under Montana's construction-contractor licensing chapter.

    • The exemption does not apply to an owner otherwise covered by the chapter who constructs a residence on the owner's property intending and for the purpose of promptly selling the improved property.
    • For an owner working on the owner's property, the resale exception does not apply if the owner has continuously occupied the property as the owner's primary residence for at least the last 12 months.
    • This is an exemption from the construction-contractor licensing chapter; it does not itself exempt a project from applicable building, electrical, plumbing, mechanical, or inspection requirements.

    primary-residence occupancy period for resale exception: >= 12 months (The statute states the owner must have continuously occupied the property as the owner's primary residence for at least the last 12 months.)

    “(13) to an owner working on the owner's property, whether occupied by the owner or not, but this exemption does not apply to an owner”
  • 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.”
    2 more reviewed findings on this topic
    • Adopted (with conditions) — Residential and commercial construction in Montana, including areas of Custer County that do not operate a certified local building-code program.
      “In addition, the program is responsible for adopting a uniform state building code, which is enforced statewide for residential and commercial buildings across Montana.”
    • Partial — Montana's statewide building-code framework for residential and commercial construction.
      “In Montana, cities, counties and towns have the option to enforce local building, electrical, plumbing, and mechanical codes, all or in part (except for state-owned agencies, which must be permitted through this Department). These local building code enforcement programs must be certified by the BC Program. The remaining cities, counties and towns that have chosen not to enforce building codes, fall under the jurisdiction of the BC Program. [...] 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.”
    One more reviewed finding on this topic
    • Required — State-permitted building projects in Custer County.
      “It is the responsibility of the permit hold to notify the inspector when work is ready for inspection and to provide access for required 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.”
  • Living in an RVLimited

    RV, camper-trailer, and other trailer overnight use for general recreation on legally accessible Montana state trust land administered by DNRC.

    • A Conservation License is required for dispersed camping on state trust land.
    • RV or trailer camping must be within 50 feet of a customary access point; motorized vehicles must be parked within 50 feet of a customary access point, and the camper or trailer may not be set up farther away by driving beyond that point.
    • On leased or licensed land, the stay limit is 2 days.
    • On unleased or unlicensed land, the stay limit is 16 days within a 30-day period.
    • Within a designated campground, the stay limit is 16 days within a 30-day period.
    • The local DNRC field office should be contacted to confirm whether land is leased.
    • Pets must be leashed or otherwise controlled.
    • Overnight horses must be restrained, may not remain in a stream riparian zone for more than one hour, and must use certified weed-seed-free feed.
    • Campfires are generally permitted within designated campgrounds and on unleased or unlicensed land but are not allowed on leased land.
    • Cutting firewood requires a separate permit from the local DNRC field office, and fireworks are not allowed on state land.
    • State Parks, Fishing Access Sites, and Wildlife Management Areas are managed by Montana Fish, Wildlife and Parks rather than under this DNRC camping page.

    RV/trailer distance from customary access point: <= 50 ft (Motorized vehicles must be parked within 50 feet; the page states the camper or trailer may not be driven farther to set it up.) · maximum stay on leased or licensed land: 2 days · maximum stay on unleased or unlicensed land: 16 days within a 30-day period · maximum stay within designated campground: 16 days within a 30-day period

    “TRAILER/RV etc. Camp within 50 ft of a customary access point. Motorized vehicles must be parked within 50 ft of a customary access point. You may not drive further to set up a camper or trailer. On leased or licensed land: 2 days On unleased/unlicensed land: 16 days within a 30-day period Within designated campground: 16 days within a 30-day period”
  • Accessory dwellingsAllowed (with conditions)

    Accessory dwelling units in jurisdictional areas where a Montana county has established zoning regulations under MCA Title 76, chapter 2, part 2.

    • The county zoning regulations must allow at least one accessory dwelling unit by right on a lot or parcel containing a single-family dwelling.
    • The unit may be attached, detached, or internal.
    • The county may not require owner occupancy, a familial, marital, or employment relationship between occupants, or impact fees; private restrictive covenants remain possible but cannot be required as a permit, license, or use condition.
    • A county may charge up to $250 for a one-time ADU application-review fee, in addition to usual building fees.
    • Applicable building codes, fire codes, and public-health and safety regulations still apply.
    • The county may require expedited sanitation review for an ADU on a parcel with existing public water and wastewater capacity; the 15-day expedited-review provision terminates September 30, 2029.
    • The statute applies to a county that exercises zoning powers; it does not itself create county zoning where none exists.

    maximum one-time application-review fee: <= 250 USD (Usual building fees may also be required.) · expedited sanitation review: 15 days (Parcel must have existing public water and wastewater service with capacity.)

    “In jurisdictional areas where the board of county commissioners has established zoning regulations under this part, the regulations must allow a minimum of one accessory dwelling unit by right on a lot or parcel that contains a single-family dwelling.”
    One more reviewed finding on this topic
    • Allowed (with conditions) — Accessory dwelling units in Montana municipalities that exercise zoning powers under MCA Title 76, chapter 2, part 3.
      “A municipality shall adopt regulations under this chapter that allow a minimum of one accessory dwelling unit by right on a lot or parcel that contains a single-family dwelling.”
  • Well permitLimited

    New groundwater developments in Montana using 35 gallons per minute or less and no more than 10 acre-feet per year.

    • All water uses starting after June 30, 1973, require a water right either through a water-use permit or an exception to the permitting process.
    • The development may qualify for the exception; qualification is not automatic.
    • Completed groundwater uses that meet the permit exception receive a Groundwater Certificate rather than a water permit.
    • A permitted water right is required for a combined appropriation from the same source by two or more wells or developed springs exceeding 10 acre-feet, regardless of flow rate.
    • All lots in a multi-phase subdivision must share a combined water-use limit of 10 acre-feet per year to qualify for a permit exception.
    • Beginning January 1, 2026, a water user intending to develop water use through a permit exception must file a Notice of Intent with DNRC before using water from an exempt well.
    • DNRC reviews a correct and complete Notice of Intent within 10 business days; if eligible, it authorizes the Notice of Intent and gives the user five years to complete the project, put the water to use, and file a Notice of Completion.
    • If the proposed use is not eligible, the Notice of Intent is denied and the user is directed to the water-right permit process.
    • The Notice of Intent filing fee is $400.
    • An authorized Notice of Intent expires after five years, with an opportunity for one five-year extension.

    maximum flow rate: <= 35 gpm · maximum annual volume: <= 10 acre-feet per year · Notice of Intent fee: 400 USD (Beginning January 1, 2026) · Notice of Intent review period: 10 business days (For a correct and complete Notice of Intent) · authorized Notice of Intent term: 5 years (One five-year extension opportunity is available)

    “Permit Exceptions, a.k.a. Exempt Wells: Small groundwater developments that use 35 gpm or less and do not exceed 10 acre-feet per year are known as “exempt wells” and may qualify for an exception to the water permit process.”
    One more reviewed finding on this topic
    • Required — Surface-water uses and groundwater uses exceeding 35 gallons per minute or 10 acre-feet per year in Montana.
      “Water Permits: A water permit is required for all surface water use and groundwater uses over 35 gallons per minute (gpm) or 10 acre-feet per year.”
  • 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”
  • 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;”
    One more reviewed finding on this topic
    • Limited — Dispersed and designated-campground temporary camping on legally accessible Montana state trust land administered by DNRC.
      “Dispersed camping is allowed on state trust land with the appropriate permit and with certain restrictions. Dispersed camping on state trust land is allowed with a Conservation License. Camping that is incidental to hunting or fishing is permitted through your conservation license, and no additional permitting is required. Group camping requires a special recreational use license. On leased or licensed land: 2 days On unleased/unlicensed land: 16 days within a 30-day period Within designated campground: 16 days within a 30-day period”
  • county zoning authorityGeneral

    Montana county boards of commissioners' authority to adopt zoning regulations, including in unincorporated portions of established jurisdictional areas.

    • The board of county commissioners must have adopted a growth policy pursuant to Title 76, chapter 1.
    • Zoning may be adopted for all or parts of the jurisdictional area in accordance with Title 76, chapter 2, part 2.
    • Within unincorporated portions of an established jurisdictional area, the board may establish zoning regulations by resolution or divide the county into zoning districts.
    • Zoning regulations may regulate the erection, construction, reconstruction, alteration, repair, location, or use of buildings or structures and the use of land.
    • An action challenging creation of a zoning district or adoption of zoning regulations must be commenced within 6 months after the board's order.
    • Regulations in one district may differ from those in other districts.
    • The statute also states that zoning regulations may not treat manufactured housing or factory-built housing units differently from other residential units, subject to the statutory presumption concerning placement.

    challenge period: 6 months (after the date of the board order creating the district or adopting the regulations)

    “For the purpose of promoting the public health, safety, morals, and general welfare, a board of county commissioners that has adopted a growth policy pursuant to chapter 1 is authorized to adopt zoning regulations for all or parts of the jurisdictional area in accordance with the provisions of this part.”
    One more reviewed finding on this topic
    • General — Montana county boards of commissioners adopting zoning regulations for all or parts of their jurisdictional areas, including unincorporated portions where the statutory prerequisites are met.
      “a board of county commissioners that has adopted a growth policy pursuant to chapter 1 is authorized to adopt zoning regulations”
  • county building authorityGeneral

    Montana counties may adopt and enforce building codes and require construction permits for residential construction in unincorporated county areas, subject to the statutory certification, geographic, code-content, and permit requirements.

    • A county may adopt a building code by ordinance or resolution, or authorize adoption by administrative action.
    • A county may adopt its building code on a countywide basis unless a city or town within the county has adopted a building code; the county may not enforce its county building code within that city or town.
    • The county code-enforcement program must be certified by the Montana Department of Labor and Industry.
    • The current adopted code, current fee list, and current enforcement plan must be filed with and approved by the Department.
    • Inspectors must satisfy the stated state-licensing or approved national-certification requirements.
    • Except for voluntary incentive-based energy-conservation standards, the county may not adopt or enforce a building code more stringent than the code adopted by the Department or required by state law.
    • The county may prohibit construction from commencing until the required permit is issued after compliance is shown.
    • The general construction-permit requirement applies to buildings subject to Title 50, chapter 60, parts 1 through 4.
    • State agency-owned buildings remain under state Department jurisdiction for plan review, permitting, and inspections.
    “The local legislative body of a county, city, or town may adopt a building code to apply to the county, city, or town by an ordinance or resolution, as appropriate: (a) adopting a building code; or (b) authorizing the adoption of a building code by administrative action.”
    One more reviewed finding on this topic
    • General — Montana counties' authority to adopt and enforce building codes and require building-code administration for construction in county areas, including unincorporated areas.
      “The local legislative body of a county, city, or town may adopt a building code to apply to the county, city, or town by an ordinance or resolution, as appropriate: (a) adopting a building code; or (b) authorizing the adoption of a building code by administrative action.”

Still unanswered

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

  • Minimum dwelling size — Minimum dwelling size in unincorporated Custer County.
  • Tiny homes — Tiny-home occupancy in unincorporated Custer County.
  • Mandatory utility hookup — Water and sewer connection requirements for Custer County property.
  • Agricultural exemption — Agricultural exemptions from Custer County development, zoning, or subdivision requirements.

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 Custer County, Montana

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

Custer County scores 49/100 on the Bolthole Index, a solid county profile. Its strengths: deep seclusion — about 216 people within 15 miles and manageable long-term carry cost. Watch-outs: weak self-sufficiency basics: only 14.5″ of rain a year.

Do you need a building permit in Custer County, Montana?

Custer County requires a building permit only in limited cases (such as floodplains or specific zones), and it enforces county zoning. Onsite septic is permitted by Custer County Environmental Health / Sanitarian (with Montana DEQ liaison). Owner-builders may act as their own contractor to build their home. These answers are quoted from official sources and independently re-checked. Rules change and cities within the county differ — always confirm with the county before you buy or build.

Can you live in an RV or tiny home on your land in Custer County?

Living in an RV on your own land in Custer County is limited to specific cases: Statewide rule. RV, camper-trailer, and other trailer overnight use for general recreation on legally accessible Montana state trust land administered by DNRC. A Conservation License is required for dispersed camping on state trust land. RV or trailer camping must be within 50 feet of a customary access point; motorized vehicles must be parked within 50 feet of a customary access point, and the camper or trailer may not be set up farther away by driving beyond that point. Confirm with the county before relying on it.

How much does land cost in Custer County, Montana?

Land in Custer County runs about $1,017 per acre, based on the latest county data.

What is the water situation in Custer County?

Custer County gets about 14.5" of rain a year, with severe drought in roughly 11.4% of years.

How remote is Custer County?

A typical private-land location has about 216 people within 15 miles and 44,850 within 100 miles. These radius catchments are the published fallback where road routing is unavailable.

How Custer compares in Montana

Compare side-by-side →See all 56 Montana counties ranked →