Lewis and Clark County, MT Building Permits & Zoning

Unincorporated Lewis and Clark County, Montana does not require a county building permit for a single-family home, and Montana exempts residential buildings with fewer than five dwelling units from its state permit unless they serve transient guests¹². County zoning applies only within designated districts, so check the parcel map before planning a build³⁴. Septic systems go through Lewis and Clark Public Health's Environmental Services Division⁵.

At a glance

Building permit: Not required for a single-family home in unincorporated Lewis and Clark County¹
State building permit exemption: Residential buildings with fewer than five dwelling units are exempt unless they serve transient guests²
Zoning: Only inside designated Part 1 and Part 2 zoning districts - check the county's interactive map for your parcel³⁴
Septic permits: Issued by Lewis and Clark Public Health's Environmental Services Division after a site evaluation⁵⁶
Minimum home size: Not regulated by the county's zoning rules⁴
Subdivision review: A pre-application meeting is required for a proposed subdivision⁷
Driveway on a state highway: Needs a separate Montana Department of Transportation approach permit⁸

Who to call

Planning & zoning

Lewis and Clark County Community Development and Planning Department

Zoning, subdivision review, floodplain development, and open lands/parks review for unincorporated Lewis and Clark County

406-447-8374

316 N. Park Ave., Room 230, Helena, MT 59623

Zoning

Lewis and Clark County Zoning (Community Development and Planning)

Explains Lewis and Clark County's Part 1 and Part 2 zoning districts and setback/lot-size rules; reached through the Community Development and Planning Department at 406-447-8374

406-447-8200

316 N. Park Avenue, Helena, MT 59623

Septic permits

Lewis and Clark Public Health - Environmental Services Division

Site evaluations and septic (on-site wastewater) permits for unincorporated Lewis and Clark County

406-457-8900

Murray Building, 1930 Ninth Avenue, Helena, MT 59601

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 Lewis and Clark County, Montana?

No. Lewis and Clark County has no residential building-permit program of its own for unincorporated land; the county's Community Development and Planning Department handles zoning, subdivision review and floodplain review instead of building codes¹. Montana's state permit exempts residential buildings with fewer than five dwelling units unless they serve transient guests, along with farm and ranch buildings and qualifying private garages and storage buildings². Covered projects must receive the state building permit before construction begins and before required plumbing, mechanical or electrical permits are issued². The state exemption applies outside certified local-government program areas; inside Helena city limits, the City of Helena requires its own building permits¹.

Who handles building-related permits in Lewis and Clark County, and how do you reach them?

Since there is no county building department, your main point of contact for land-use questions is the Lewis and Clark County Community Development and Planning Department, which coordinates zoning, subdivision review, floodplain development, open lands and historic preservation⁹. Reach the department at 406-447-8374, or visit the City-County Building at 316 N. Park Ave., Room 230, Helena, MT 59623, Monday through Friday from 8:00 am to 5:00 pm⁹. Montana's Building Codes Program handles projects that require a state building permit, and the permit holder must notify the inspector when covered work is ready and provide access for required inspections¹⁰. Ask the Planning Department about floodplain review and subdivision review before finalizing the site plan⁹.

Does Lewis and Clark County have zoning, and what does it mean for RVs, tiny homes and setbacks?

Zoning is not countywide: Lewis and Clark County uses Part 1 and Part 2 zoning, and only parcels inside an established district are zoned³⁴. Part 2 regulations cover the Helena Valley and the Fort Harrison rural and urban growth areas, while the county has several Part 1 districts⁴. Use the county's interactive mapping site to identify the parcel's district before planning around setbacks or uses⁴. The county's zoning regulations do not set a minimum size or price for houses⁴. We could not confirm a countywide RV- or tiny-home occupancy rule, so ask the Planning Department what applies to the parcel⁹.

How do septic permits work in Lewis and Clark County?

Septic systems in unincorporated Lewis and Clark County are permitted by the county's Environmental Services Division, part of Lewis and Clark Public Health, at their office in the Murray Building on Ninth Avenue in Helena⁶. Before you can get a septic permit you generally need a site evaluation of the soils, topography and water quality on your parcel, unless you already hold a DEQ subdivision approval or a previous site approval that still meets current regulations⁶. Site evaluation fees run $480 for a new site including the required non-degradation review, $400 for a replacement system or review of an existing system, and $80 for an individual non-degradation review alone, and the county has up to 20 working days to approve or deny the evaluation⁶. Once you have an approved site evaluation, permit fees depend on the system and installer: a certified installer pays $160 for a standard gravity system versus $320 for a non-certified installer, and only certified installers may install a pressure-dosed system at $320, an individual engineered system at $480, or a multi-user/public system at $720; a septic tank permit is $80 and a holding tank permit is $160 regardless of installer⁶. Start construction before your permit is issued and the fee doubles, with possible added penalties, and once issued a permit expires one year from the date it was granted⁶. Even if your subdivision already has a Montana DEQ Certificate of Subdivision Approval, that certificate does not replace the county's drainfield permit, so you still need one¹¹⁶.

Can you live in an RV or tiny home on your land in Lewis and Clark County?

We could not confirm a countywide rule for living in an RV or tiny home on private land in unincorporated Lewis and Clark County. Zoning applies only inside designated Part 1 and Part 2 districts, so check the county's interactive map and ask the Community Development and Planning Department what applies to the parcel³⁴⁹. A residential structure that needs wastewater disposal and is not connected to municipal sewer requires a county septic permit⁶. A land division that creates qualifying RV or mobile-home rental spaces can also trigger county subdivision review⁷.

Building a home in Lewis and Clark County: the steps, in order

Check the county's interactive map and ask Community Development and Planning what the parcel's zoning and floodplain status allow⁴⁹.
If the project divides land into qualifying parcels or creates multiple RV or mobile-home rental spaces, schedule the required subdivision pre-application meeting before applying⁷.
Order a septic site evaluation unless the parcel has a qualifying DEQ subdivision approval or prior site approval; the county may take up to 20 working days⁶.
Arrange a test hole, obtain a nearby well-water sample if required, and prepare a general facilities plan for the site evaluation⁶.
Confirm that the home fits the state exemption; covered projects need a state building permit before construction and before required trade permits².
If a state permit is required, notify the inspector when work is ready and provide access for required inspections¹⁰.
Obtain an MDT approach permit or right-of-way agreement before building a new or modified driveway onto a state highway⁸.
Obtain the septic permit before any construction, including well drilling or foundation excavation, to avoid a doubled fee and possible penalties⁶.

What to check before you buy land in Lewis and Clark County, Montana

Ask Lewis and Clark Public Health's Environmental Services Division about a site evaluation before you commit to a parcel: only about 7.2% of the county's soils are rated free of severe limitations for a conventional septic drain field, and sites with shallow groundwater or bedrock face extra restrictions, since state and local rules require at least 4 feet of separation between a drain field trench and both the water table and bedrock¹²⁶. Check the county's interactive zoning map, since zoning in Lewis and Clark County only applies inside established Part 1 and Part 2 districts and rules differ sharply where it does apply⁴. About 51.1% of the county is federal land, which affects both access and what is actually available to buy¹³. Only 26.8% of the county's land sits at 15% slope or gentler, so ask about slope and access before you assume a building site will be easy to grade¹⁴. Confirm how your access road connects: a new or modified driveway onto a state highway needs a Montana Department of Transportation approach permit or right-of-way agreement, while a driveway onto a county road is a local matter to confirm with the county⁸. Lewis and Clark County's median property tax bill is about $2,886 a year at an effective rate near 0.8%, and typical homes in the county are valued around $471,902¹⁵¹⁶¹⁷.

Watch-outs

Land divisions creating qualifying parcels under 160 acres, condominiums, or multiple RV or mobile-home rental spaces require subdivision review, including a pre-application meeting; lots cannot be transferred until final approval and recording⁷.
Starting septic construction before your permit is issued doubles the permit fee and may add penalties, and a septic permit expires one year after it is issued, so time your application to your construction schedule⁶.

Sources

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.

How Lewis and Clark County scores

Seclusion90100% ev.

Self-Sufficiency44100% ev.

Admin Boringness6690% ev.

Durability55100% ev.

Property Autonomy83100% ev.

Carry Cost77100% 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 →

$472kTypical home

0.8%Property tax

$1,762Land / acre

22.3"Annual rain

14.6% of yrsSevere drought

0.6 / yr (+0.6)Mid-century 100°F days

18.9 daysMid-century dry spell

1.36" (+8.9%)Mid-century 1-day rain

1.25×Wildfire change factor

100%Forward climate coverage

$1,729Home insurance / yr

1.2% / yrInsurance growth

0.76%Nonrenewal rate

county median (2+ published ZIPs)Insurance basis

150People within 30 min

168,709People within 2 hr

1,043Radius comparison (15 mi)

21.7People / sq mi

51.1%Federal land

26.8%Land at 15% slope or less

7.2%Septic soil without severe limits

150,456 acWorkable land screen

54.2%Wooded land

20.9 tonsBiomass / forest ac

41.2°FAvg temp

Answers from the rulebook for Lewis and Clark County

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

Lewis and Clark County rules

Subdividing landRegulated (with conditions)
Land divisions creating one or more parcels under 160 acres, condominiums, and areas providing multiple rental or lease spaces for recreational vehicles or mobile homes.
- Major subdivisions contain 6 or more lots, units, or spaces.
- First minor subdivisions contain 5 or fewer lots, units, or spaces on qualifying tracts.
- Subsequent minor subdivisions contain 5 or fewer lots, units, or spaces that are not first minor subdivisions.
- Review generally has preliminary and final plat stages.
- A pre-application meeting is required before applying.
- Lots may not be transferred until final approval and recording of subdivision documents and mylars.
acreage threshold: < 160 acres (exclusive of public roadways and subject to statutory definition)
“Prior to making application for a subdivision, a pre-application meeting is required”
Subdivision Review ↗Re-checked Sep 26, 2026
County-wide zoningPresent
Lewis and Clark County administers zoning through its Community Development and Planning Department, but zoning applies only within designated county zoning districts; much of the unincorporated county is unzoned.
Lewis & Clark County - Zoning ↗Scouted from the county site, not yet independently re-checked

Montana rules that apply here

Building permitLimited
State building permits in Montana state jurisdiction applicable to covered projects in Lewis and Clark County.
- A state permit is required before construction for certain new buildings and alterations, additions, and repairs.
- Permits must be issued before plumbing, mechanical, or electrical permits and before work under those permits starts.
- 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 when not part of a commercial enterprise or business.
- The state requirement does not apply to projects within the jurisdictional limits of a certified local government program.
residential dwelling units: < 5 dwelling units (exempt except when serving transient guests)
“a state building permit is required prior to the start”
Building Permits ↗Re-checked Sep 26, 2026
One more reviewed finding on this topic
- Limited — Construction, remodeling, moving, alterations, additions, repairs, or changes of occupancy for buildings subject to Montana state building-code jurisdiction.
  “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 Permits ↗Re-checked Sep 11, 2026
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.”
Current Codes ↗Re-checked Sep 11, 2026
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.”
Building Permits ↗Re-checked Sep 11, 2026
One more reviewed finding on this topic
- Limited — Required inspections for projects subject to Montana state building permits.
  “provide access for required inspections.”
  Building Permits ↗Re-checked Sep 26, 2026
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.”
50-60-107. Certificate of occupancy, MCA ↗Re-checked Sep 11, 2026
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.”
Engineering Infrastructure & Subdivisions ↗Re-checked Sep 11, 2026
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.”
Engineering Infrastructure & Subdivisions ↗Re-checked Sep 11, 2026
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.”
Approach Manual for Landowners and Developers ↗Re-checked Sep 11, 2026
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).”
Stream Permitting ↗Re-checked Sep 11, 2026
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”
Property Management Program ↗Re-checked Sep 11, 2026
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.”
Frequently Asked Questions ↗Re-checked Sep 11, 2026
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.”
Building Permits ↗Re-checked Sep 11, 2026
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;”
Public Use Rules and Regulations ↗Re-checked Sep 11, 2026
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”
76-2-201. County zoning authorized, MCA ↗Re-checked Sep 21, 2026

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 in Lewis and Clark County.
Local zoning — Local zoning in incorporated and unincorporated areas of Lewis and Clark County.
Zoning districts — Published zoning districts and district regulations in Lewis and Clark County.
Minimum dwelling size — Minimum dwelling size requirements in Lewis and Clark County.
Minimum lot size — Minimum lot-size requirements in Lewis and Clark County.

12 more unanswered

Setbacks
Lot coverage
Building height
Living in an RV
Camping on your land
Tiny homes
Manufactured homes
Accessory dwellings
Off-grid sanitation
Well permit
Mandatory utility hookup
Agricultural exemption

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 Lewis and Clark 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) ↗

North Valley Controlled Groundwater Area (East Helena)localized of county
Contamination-driven CGWA near East Helena (former ASARCO smelter); new wells require a permit plus local health approval.
Montana DNRC — Basin Closures and Controlled Ground Water Areas ↗

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 Lewis and Clark County, Montana

Is Lewis and Clark County a good place to live off-grid or homestead?

Lewis and Clark County scores 77/100 on the Bolthole Index, a strong county profile. Its strengths: deep seclusion — about 150 people within a 30-minute drive and a stronger property-autonomy legal backdrop.

Do you need a building permit in Lewis and Clark County, Montana?

Lewis and Clark County does not require a county building permit for a home in unincorporated areas, and it enforces county zoning. Onsite septic is permitted by Lewis and Clark Public Health, Environmental Services Division. 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 Lewis and Clark County, Montana?

Land in Lewis and Clark County runs about $1,762 per acre, based on the latest county data.

What is the water situation in Lewis and Clark County?

Lewis and Clark County gets about 22.3" of rain a year, with severe drought in roughly 14.6% of years. On water rights, Lewis and Clark County lies in the North Valley Controlled Groundwater Area (East Helena) — Contamination-driven CGWA near East Helena (former ASARCO smelter); new wells require a permit plus local health approval..

How remote is Lewis and Clark County?

A representative private-land location has about 150 people within a 30-minute drive and 168,709 within two hours. The road-network catchments count population across county lines and clusters of smaller cities; straight-line radius values remain available as a comparison.

Building permits, zoning and septic rules in Lewis and Clark County, Montana

At a glance

Who to call

Do you need a building permit in Lewis and Clark County, Montana?

Who handles building-related permits in Lewis and Clark County, and how do you reach them?

Does Lewis and Clark County have zoning, and what does it mean for RVs, tiny homes and setbacks?

How do septic permits work in Lewis and Clark County?

Can you live in an RV or tiny home on your land in Lewis and Clark County?

Building a home in Lewis and Clark County: the steps, in order

What to check before you buy land in Lewis and Clark County, Montana

Watch-outs

Sources

Lewis and Clark County in Montana

How Lewis and Clark County scores

Find land. Bring the promising ones back.

Parcel due diligence

Answers from the rulebook for Lewis and Clark County

Lewis and Clark County rules

Montana rules that apply here

Still unanswered

Water rights & wells in Lewis and Clark County

Living off-grid in Lewis and Clark County, Montana

Is Lewis and Clark County a good place to live off-grid or homestead?

Do you need a building permit in Lewis and Clark County, Montana?

How much does land cost in Lewis and Clark County, Montana?

What is the water situation in Lewis and Clark County?

How remote is Lewis and Clark County?

How Lewis and Clark compares in Montana