Bolthole Index

Yellowstone County, Montana

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

55Index Score / 100
#35 of 56 in Montana

Unincorporated Yellowstone County, Montana does not require a county building permit for a single-family home, and Montana exempts residential buildings with fewer than five units, outside certified cities, from the state building permit too.1 The county does have zoning, administered jointly with the City of Billings' Planning Division and enforced through the Yellowstone County Zoning Commission.2 Septic systems go through RiverStone Health, the local health department, not the county.3 Only about 19.1% of the county's soils are rated free of severe limits for a conventional drain field, so plan for a site evaluation before you count on a standard system.4

At a glance

Building permit
Not required outside Billings city limits for a single-family home1
Zoning
Yes, countywide, via the joint City/County Planning Division and Zoning Commission2
Septic permit
Issued by RiverStone Health (local health department), not the county3
Owner-builder exemption
Montana does not restrict owner-builders from constructing their own single-family home5
Subdivision review
Parcels under 20 acres go through Montana DEQ; 20 acres or more go through local review3
Septic soils
About 19.1% of soils are free of severe limits for a conventional drain field4
Floodplain permit
Required for new development in a mapped Special Flood Hazard Area6

Who to call

Zoning

City-County Planning Division (Yellowstone County / City of Billings)

Zoning permits, zoning changes, variances, special use permits and subdivision applications for unincorporated Yellowstone County

(406) 657-8247

316 N. 26th Street, Billings, MT 59101

Online permits →

Septic permits

RiverStone Health, Environmental Health Services

Septic (on-site wastewater) permits and subdivision sanitation review for Yellowstone County

406.256.2770

123 South 27th Street, Billings, MT 59101

Floodplain permits

Yellowstone County Floodplain Administration (Public Works)

Floodplain permits and floodplain determinations for unincorporated Yellowstone County

406-256-2735

[email protected]

Online permits →

Contact details are copied from each office’s official page and were checked against it on September 24, 2026.

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

No, not from the county, for a typical single-family home outside Billings city limits. Yellowstone County does not issue building permits, and Montana law exempts "residential buildings containing less than five dwelling units except when serving transient guests" from the state building permit, along with farm and ranch buildings and private garages and storage buildings for the owner's own use.17 Montana does adopt a uniform state building code, enforced statewide for buildings that do need a permit, and does not restrict an owner from building their own single-family residence.85 Skipping a county building permit does not skip everything else: you still need a zoning permit from the Planning Division, a septic permit from RiverStone Health if you're not on sewer, and a floodplain permit if your parcel is in a mapped flood zone.91011

Who handles zoning, floodplain and permits in Yellowstone County, and how do you reach them?

Zoning for unincorporated Yellowstone County runs through the City-County Planning Division, a joint agency with the City of Billings, at (406) 657-8247, 316 N. 26th Street, Billings, MT 59101, or through its CityView online portal.9 The division "provides community planning and development services to Yellowstone County, the City of Billings, and the Town of Broadview," and its staff supports the county's Zoning Commission and Board of Adjustment.9 Floodplain permits and determinations come from Yellowstone County's own Floodplain Administration (Public Works), reachable at 406-256-2735 or [email protected]; the department confirms "the floodplain regulations shall apply to all lands within the jurisdiction of the County of Yellowstone, Montana."11 Septic permits come from RiverStone Health, the local health department, at 406.256.2770, 123 South 27th Street, Billings, MT 59101.10

Does Yellowstone County have zoning?

Yes. Unincorporated Yellowstone County is zoned, administered jointly by the City-County Planning Division and the Yellowstone County Zoning Commission.2 Montana law lets a county's board of commissioners adopt zoning once it has adopted a growth policy, and Yellowstone County has done so.12 The Planning Division reviews "proposed projects and processing subdivision applications, applications for requests for zoning changes and variances, and special use permits" for the county.9 Because zoning here is administered separately from the building-permit exemption, don't assume a lack of building permits means a lack of land-use rules: confirm your parcel's zoning district, any setbacks and any use restrictions with the Planning Division before you buy or build.

How do septic permits work in Yellowstone County?

Septic systems in Yellowstone County are permitted by RiverStone Health, not the county government.3 The review path depends on lot size: "parcels less than 20 acres in size are subject to the Montana Department of Environmental Quality (DEQ) review and approval process," while "parcels 20 acres or more are subject to the local review process" run by RiverStone Health directly.10 To get a septic permit, you first obtain a permit tracking sheet from the Yellowstone County Courthouse, Room 305, which confirms your address is assigned, an approach permit has been issued, and the property is not in a floodplain, before RiverStone Health will review your lot layout.10 At installation, RiverStone Health's Environmental Health Services must inspect the system before it can be placed into use.10 Soils are a genuine constraint countywide: only about 19.1% of Yellowstone County's soils are rated free of severe limits for a conventional drain field, so budget for a site evaluation rather than assuming a standard system will work.4

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

Reviewed sources do not confirm a specific countywide rule for RV or tiny-home living on a private unincorporated lot in Yellowstone County. Since the county has zoning administered by the City-County Planning Division, ask that office directly which district covers your parcel and whether it allows RV or manufactured-home occupancy before you buy or move a unit in.9 Montana's camping rules limiting stays to 7 nights per 30-day period and barring overnight camping without someone present apply to Fish, Wildlife & Parks public-use sites, not to what you can park or live in on your own land, so don't treat them as an answer here.13 Because the county does not require a building permit for a single-family home outside Billings, a manufactured or modular home may face fewer building-permit hurdles than in many counties, but zoning, septic and floodplain rules still apply the same as for a stick-built house.12

Building a home in Yellowstone County: the steps, in order

  1. Confirm with the City-County Planning Division that your parcel's zoning district allows the home you plan to build, and get any required zoning permit.9
  2. Confirm the property is not in a mapped Special Flood Hazard Area, or get a floodplain permit from the county's Floodplain Administration if it is.116
  3. If your driveway connects to a state highway, apply for an approach permit or right-of-way agreement from the Montana Department of Transportation district office before building it.14
  4. For septic, first verify DEQ or local sanitation review (DEQ for parcels under 20 acres, local review for 20 acres or more), then get a permit tracking sheet from the Yellowstone County Courthouse, Room 305.10
  5. Submit the tracking sheet, a detailed lot layout and the required fee to RiverStone Health for septic system approval and specifications.10
  6. Because a county building permit generally isn't required for a single-family home outside Billings, confirm separately whether your project needs electrical, plumbing or mechanical permits, which can still apply even when the building permit itself is exempt.17
  7. Call RiverStone Health's Environmental Health Services to schedule the septic inspection before the system is covered or placed into use.10

What to check before you buy land in Yellowstone County

Confirm your parcel's zoning district and any use restrictions with the City-County Planning Division, since the county does have zoning even though it skips a county building permit.921 Check with the Floodplain Administration whether the parcel sits in a mapped Special Flood Hazard Area; Yellowstone County is currently updating its floodplain regulations, so ask what's changing before you close.11 Budget for septic due diligence: with only about 19.1% of soils rated free of severe limits for a conventional drain field, a site evaluation should come before you finalize your build plan.4 The county gets only about 14.6 inches of precipitation a year and sees severe drought in roughly 12.3% of years, so plan your water supply and any well with that dryness in mind.1516 Typical property tax runs about a 0.8% effective rate with a median bill near $2,669 a year, and a typical homeowner's insurance premium runs closer to $2,302 a year, both worth building into your budget.171819

Watch-outs

  • Yellowstone County is currently updating its floodplain regulations and is taking public comment through its Public Works floodplain contact; confirm which rules apply to your parcel before you buy or build near a flood-prone area.11
  • Skipping a county building permit does not skip zoning, septic or floodplain review in Yellowstone County; confirm all three separately before you build.12
  • Septic review differs by lot size: parcels under 20 acres go through Montana DEQ, while parcels of 20 acres or more go through RiverStone Health's local review process.10

Sources

  1. Yellowstone County Public Works General Information (2026 county census)
  2. Yellowstone County Zoning Code (2025) (2026 county census)
  3. RiverStone Health - Septic Permits & Subdivision Review (2026 county census)
  4. Share of soils without severe limits for a conventional septic drain field (USDA SSURGO): Bolthole Index county data
  5. Yellowstone County Public Works General Information (2026 county census)
  6. Stream Permitting (Montana statewide rule), quoted and re-checked
  7. Building Permits (Montana statewide rule), quoted and re-checked
  8. Current Codes (Montana statewide rule), quoted and re-checked
  9. City-County Planning Division (Yellowstone County / City of Billings) (billingsmt.gov)
  10. RiverStone Health, Environmental Health Services (riverstonehealth.org)
  11. Yellowstone County Floodplain Administration (Public Works) (yellowstonecountymt.gov)
  12. 76-2-201. County zoning authorized, MCA (Montana statewide rule), quoted and re-checked
  13. Public Use Rules and Regulations (Montana statewide rule), quoted and re-checked
  14. Approach Manual for Landowners and Developers (Montana statewide rule), quoted and re-checked
  15. Annual precipitation: Bolthole Index county data
  16. Share of years in severe drought: Bolthole Index county data
  17. Effective property tax rate: Bolthole Index county data
  18. Median property tax bill: Bolthole Index county data
  19. Typical home insurance premium: Bolthole Index county data

Written September 24, 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

Yellowstone County in Montana

55
County map
Yellowstone County highlighted among the Montana counties · colored by Index score

How Yellowstone County scores

Seclusion75100% ev.
Self-Sufficiency18100% ev.
Admin Boringness72100% ev.
Durability62100% ev.
Property Autonomy83100% ev.
Carry Cost77100% ev.

Evidence strength: 100%. This reports direct-source completeness and fallback use; it is separate from the score and is not a confidence interval. How it works →

$403kTypical home
0.8%Property tax
$1,216Land / acre
14.6"Annual rain
12.3% of yrsSevere drought
10.5 / yr (+9.2)Mid-century 100°F days
20.6 daysMid-century dry spell
0.99" (+6.2%)Mid-century 1-day rain
1.25×Wildfire change factor
100%Forward climate coverage
$2,302Home insurance / yr
2.2% / yrInsurance growth
0.58%Nonrenewal rate
county median (2+ published ZIPs)Insurance basis
8,697Radius comparison (15 mi)
64.9People / sq mi
4.7%Federal land
78.7%Land at 15% slope or less
19.1%Septic soil without severe limits
305,240 acWorkable land screen
4.8%Wooded land
7.4 tonsBiomass / forest ac
46.6°FAvg temp

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Answers from the rulebook for Yellowstone County

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

Yellowstone County rules

  • Building permitNot required

    County-issued building permits for structures outside the Billings city limits.

    • This is limited to Yellowstone County issuance outside Billings city limits; it does not establish requirements within Billings or other local jurisdictions.
    • Separate state permit requirements and exemptions may still apply.
    “Yellowstone County does not issue Building Permits or Certificates of Occupancy for structures outside the city limits of Billings. These structures are not subject to the same restrictions and permits as those located within the city limits.”
  • Owner-builder exemption · follows from the permit answerNot needed

    Unincorporated Yellowstone County: no county building permit is required, so there is no permit to be exempt from and you may build your own home. State licensing for electrical, plumbing and HVAC work may still apply.

    • This is limited to Yellowstone County issuance outside Billings city limits; it does not establish requirements within Billings or other local jurisdictions.
    • Separate state permit requirements and exemptions may still apply.
    “Yellowstone County does not issue Building Permits or Certificates of Occupancy for structures outside the city limits of Billings. These structures are not subject to the same restrictions and permits as those located within the city limits.”
  • Certificate of occupancyNot required

    County-issued certificates of occupancy for structures outside the Billings city limits.

    • This is limited to Yellowstone County issuance outside Billings city limits; it does not establish requirements within Billings or under another authority.
    “Yellowstone County does not issue Building Permits or Certificates of Occupancy for structures outside the city limits of Billings. These structures are not subject to the same restrictions and permits as those located within the city limits.”
  • Driveway accessRequired

    Construction of a new approach or modification of an existing approach accessing a County-managed road right-of-way.

    • The rule applies only where access is onto a right-of-way managed by Yellowstone County.
    • Construction may not begin until the County Public Works Department issues an approach permit.
    • Completion is due within one year of permit issuance; failure requires a new application and another fee.

    completion deadline: 1 year (A new application and another application fee are required if incomplete.)

    “A property owner shall obtain a permit from the Yellowstone County Public Works Department for the construction of a new approach or the modification of an existing approach that provides access onto a right-of-way managed by the County.”
  • Building in a floodplainLimited

    Development subject to Yellowstone County floodplain regulations.

    • Property-specific permit applicability must be determined with the Floodplain Office using the property's legal description.
    • When a floodplain permit is required, requirements vary with each property.
    • A non-refundable $50 processing fee is submitted with each permit or variance application; the County states that it covers processing, public notice, and sufficient field inspections.

    permit or variance processing fee: 50 USD (Non-refundable; applies with each permit and/or variance application.)

    “Please check with the Floodplain Office to determine whether you need a Floodplain permit for building projects. In order to determine whether your property is located in the floodplain or not, you will need the Legal Description of the property.”
  • Permit feesPublished (with conditions)

    Private or public access connecting to a county or dedicated road.

    • The stated fees concern access permits, not all county permit categories.
    • The County may require a contractor's excavation bond and reviews access for proper sight distance.

    residential access permit fee: 75 USD (Access connecting to a county or dedicated road.) · commercial access permit fee: 150 USD (Access connecting to a county or dedicated road.)

    “Any private or public access that connects to a county or dedicated road will need to be permitted. A permit for a residential access is $75.00 and a commercial access is $150.00.”
  • Permit processPublished (with conditions)

    New or modified driveway approaches accessing a County-managed right-of-way.

    • A permit must issue before construction in the County-managed right-of-way.
    • The owner has one year from issuance to complete construction or modification; otherwise a new application and fee are required.
    • A general site plan must show approach location, culvert diameter if applicable, distances to existing approaches and property lines, and approximate building location.

    completion deadline: 1 year (Measured from issuance; a new application and fee are required if work is not complete.)

    “A property owner shall obtain a permit from the Yellowstone County Public Works Department for the construction of a new approach or the modification of an existing approach that provides access onto a right-of-way managed by the County. A property owner shall not perform any construction on a new or existing approach in the right-of-way of a road managed by the County until the Department has issued an approach permit.”
  • County-wide zoningPresent

    Unincorporated Yellowstone County is subject to county zoning administered by the City/County Planning Division and the Yellowstone County Zoning Commission.

    Yellowstone County Zoning Code (2025) ↗Scouted from the county site, not yet independently re-checked

Montana rules that apply here

  • 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.”
  • 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.”
  • 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;”
  • 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.

  • Local zoning — Local zoning within Yellowstone County, including incorporated and unincorporated areas.
  • Zoning districts — Published zoning districts in Yellowstone County.
  • Minimum dwelling size — Minimum dwelling size in Yellowstone County.
  • Minimum lot size — Minimum lot size in Yellowstone County.
  • Setbacks — Residential setbacks in Yellowstone County.
13 more unanswered
  • Lot coverage
  • Building height
  • Living in an RV
  • Camping on your land
  • Tiny homes
  • Manufactured homes
  • Accessory dwellings
  • Septic inspection
  • Off-grid sanitation
  • Well permit
  • Mandatory utility hookup
  • Agricultural exemption
  • Subdividing land

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.

Water rights & wells in Yellowstone County

Whether a new home can legally get its own water here — the sub-state groundwater regime, from Montana’s water agency.

Actively managed

This basin is under active state management — new water use is scrutinized, though a domestic well is usually still allowed.

Household wellExempt up to a limit

Montana's exempt-well exception (85-2-306 MCA) was tightened after Upper Missouri Waterkeeper v. DNRC (2024), and from Jan 1, 2026 appropriators must file a Notice of Intent with DNRC before putting exempt groundwater to use.

Limit: 35 gpm or less AND ≤10 acre-ft/yr; a combined appropriation exceeding 10 acre-ft needs a permit regardless of flow rate

Montana DNRC — Water Rights Permit Exceptions (Exempt Wells) ↗

Prior-appropriation state (first in time, first in right). Groundwater rules change and basin boundaries follow the aquifer, not the county line — confirm current well and appropriation rules with the Montana state water agency before you buy or drill.Groundwater governance as of Jul 2026, cited to each administering agency.

Living off-grid in Yellowstone County, Montana

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

Yellowstone County scores 55/100 on the Bolthole Index, a solid county profile. Its strengths: a stronger property-autonomy legal backdrop and manageable long-term carry cost. Watch-outs: weak self-sufficiency basics: only 14.6″ of rain a year.

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

Yellowstone County does not require a county building permit for a home in unincorporated areas, and it enforces county zoning. Onsite septic is permitted by RiverStone Health, Environmental Health Services (Yellowstone County local health department). 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.

How much does land cost in Yellowstone County, Montana?

Land in Yellowstone County runs about $1,216 per acre, based on the latest county data.

What is the water situation in Yellowstone County?

Yellowstone County gets about 14.6" of rain a year, with severe drought in roughly 12.3% of years. On water rights, Yellowstone County lies in the Lockwood Solvent Groundwater Plume Controlled Groundwater Area — ~331 acres east of Billings; contamination-driven CGWA where new wells require a permit..

How remote is Yellowstone County?

A typical private-land location has about 8,697 people within 15 miles and 274,951 within 100 miles. These radius catchments are the published fallback where road routing is unavailable.

Off-grid gear

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

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How Yellowstone compares in Montana

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