Custer County has no building department. On land inside a County zoning district, a landowner needs a zoning conformance permit from the County Zoning Department at 1010 Main Street, Miles City (406-874-4024) before building or expanding a structure; site plan review costs $100 for a residential project and $200 for a commercial one, and the regulations allow 30 working days for a decision on a complete application. The County’s zoning map shows which parcels are zoned. The Miles City Building Department permits construction inside the city, and the State permits commercial buildings in the rest of the county.
What needs a permit in Custer County?
Three sets of rules can apply to one project: County zoning, County floodplain and wastewater rules, and the state building code.
- Zoning conformance permit: required before construction or expansion of a structure in any County zoning district. Site plan review is part of it for a new commercial building or use, an industrial building or use, and a residential building.
- Conditional use permit: for the uses each zoning district lists as conditional, decided by the Board of Adjustment.
- Fence and sign permits: both appear on the County’s zoning fee schedule; a fence permit covers new and replacement fences.
- Floodplain permit: for development in a designated floodplain outside Miles City and Ismay. A conformance permit for a non-residential use or structure in the floodplain is held until the floodplain permits are issued.
- Wastewater permit: for a new, upgraded or replacement septic system.
The only zoning exemption the regulations give is an accessory structure smaller than 100 square feet that still meets the district’s development standards.
On the building code, the County regulations send owners to the Montana Department of Labor and Industry. Outside Miles City the State requires a building permit for commercial buildings and for residential buildings of 5 or more units, and does not require one for a smaller house, a farm or ranch building or a private garage.
Who issues permits in Custer County?
| Office | What it handles | Contact |
|---|---|---|
| Custer County Zoning Department | Zoning conformance, site plan review, conditional use, sign, fence and floodplain permits | 1010 Main Street, Suite 2, Miles City; 406-874-4024 |
| Custer County Environmental Health | Onsite wastewater permits, subdivision sanitation review, stormwater | custeres@custercountymt.gov; the State’s list of county sanitarians gives a contract office in Billings for Custer County, 406-366-1424 |
| Miles City Building Department | City building, siding, roofing and fence permits; residential electrical permits; mechanical permits | 17 S. 8th Street, Miles City, MT 59301; 406-874-8611; Monday to Friday, 7 a.m. to 4 p.m. |
| Montana Building Codes Program | State building, electrical, plumbing and mechanical permits | 406-841-2056 |
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- Miles City (population 8,450): certified by the State inside city limits for building, mechanical and pools, and for electrical work on residential buildings only (the State’s printable list, updated October 7, 2026). Gabe Martinsen is the Building Inspector. County zoning and floodplain regulations stop at the city boundary; the City Code has its own floodplain chapter, with a City floodplain permit for work in a regulated flood hazard area.
- Ismay (population 21): not certified, so the state rules apply to building. The County’s 2016 zoning regulations and its floodplain regulations also exclude the Town of Ismay.
County and city applications
The County Land Use page posts each form as a PDF. The Zoning Department asks for one digital copy of every item in PDF, unless the Zoning Administrator waives that, along with the paper copies.
- Site Plan Review Application (revised January 14, 2026): the application behind the Land Use and Zoning Compliance Permit, for residential, commercial and industrial projects. A Sample Site Plan is posted with it.
- Sign Permit Application.
- Conditional Use Permit Application, with a how-to brochure.
- Zone Change Application.
- Floodplain development: the State’s Joint Application, filed with the County.
- Application for Wastewater Treatment System and the certified installer report form.
Miles City uses the Cloudpermit portal for building, residential electrical and roofing permits, contractor registration and business licences. For the siding and mechanical permits it added in 2026, the City’s notice gives the Building Department on 406-874-8611. A paper building permit application can be emailed or handed to the Building Inspector instead, and a fence-only permit has its own form.
Custer County permit fees
Zoning fees come from the schedule the County posts as its 2021 Zoning Fees Schedule. Floodplain fees were reset by Resolution 2026-21 on April 2, 2026, and septic fees are printed on the wastewater application.
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Get a free quote →| Item | Fee |
|---|---|
| Site plan review | $100 residential; $200 commercial |
| Zoning compliance review | $200 |
| Conditional use permit | $555 residential; $835 commercial |
| Variance | $490 residential; $590 commercial |
| Zoning clarification | $60 written; $100 with an on-site visit |
| Fence permit, new or replacement | $25 |
| Sign | $1.55 per sq ft, each face |
| Floodplain permit, simple application | $550; $800 after the fact |
| Floodplain permit, complex application | $950; $1,200 after the fact |
| Floodplain variance | $550 plus the floodplain permit fee |
| Septic permit, gravity system | $200 |
| Septic permit, pressure dose system | $350 |
| Septic permit, Level II system | $550 |
Floodplain fees are non-refundable and paid to the County Treasurer. A simple floodplain application is one that needs no encroachment analysis, map revision or work in the waterway; bridges, levees, bank stabilization, channel work and water diversions count as complex. A septic permit lasts 12 months, and $50 continues it for another year.
In Miles City, the fence permit form shows a $100 fee. The City Council sets building permit and plan review fees by resolution under Ordinance 1406, adopted July 28, 2026. The code section that ordinance replaced added a plan review fee of 30% of the permit fee to any project valued at $50,000 or more; ask the Building Department (406-874-8611) for the fee under the resolution now in force.
Electrical, plumbing and mechanical permits
The Miles City Building Department permits electrical work on residential buildings and, since July 1, 2026, residential mechanical work; its March 2026 notice also lists commercial mechanical permits. Commercial electrical work and all plumbing in the city are state permits, and so are all 3 trades in the rest of Custer County. The City’s building permit application asks applicants to mark whether a state electrical permit and a state plumbing permit are needed for the job.
Site plan review: what to submit
The County’s Site Plan Review Application needs the form, the fee, a vicinity map and a site plan drawn at a suitable scale; the form gives 1 inch to 10 feet as an example. The site plan has to show at least:
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- Name and address of the applicant
- Legal description and boundary lines
- Existing and proposed land use on the site
- Owners and land uses of adjacent property
- Location, size, dimensions and uses of existing and proposed buildings
- Utilities and related easements
Access and screening
- Streets, roads and rights-of-way with dimensions
- Curb cuts and access points
- Off-street parking spaces, driveways and surface type
- Existing and proposed landscaping or buffering
- Fencing and screening, with type and height
- Screening around outdoor storage of materials, products, machinery and equipment
A wastewater application will not be accepted without a site plan showing the parcel, the house site and all buildings, the slope, any well, stream or floodplain within 100 feet, areas of high groundwater and a 100% replacement absorption area. Where the property has no state approval, the form also asks for a soil profile to a depth of at least 8 feet.
How to apply: Custer County steps
Look up the parcel on the County zoning map, or ask the Zoning Department (406-874-4024) whether it lies in a zoning district; land inside Miles City follows the City’s rules instead.
If the site is in a designated floodplain, talk to the Zoning Administrator, who also administers the floodplain regulations.
Submit the form, fee, vicinity map and site plan to the Zoning Department at 1010 Main Street, Suite 2.
Email Environmental Health (custeres@custercountymt.gov) before sending the wastewater application and site plan: the form prints a return address of County Sanitarian, PO Box 743, Lewistown, MT 59457, while the State lists a Billings contract office for the county. The fee is $200, $350 or $550 by system type, with the check made out to Custer County.
File state building and trade permits where they apply, or apply to the Miles City Building Department, through Cloudpermit, for work inside the city.
Give the Sanitarian 24 hours’ notice before the septic system is backfilled, and obtain the Final Certificate of Zoning Compliance.
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The zoning regulations set the clock for site plan review. The Zoning Administrator has 5 working days to decide whether an application is complete, 30 working days from completeness to make a decision unless the applicant agrees to more time, and 15 working days after that to send the decision. The conformance permit is issued with an approval. Requests for more information suspend the review period.
By signing the application, the owner allows County staff onto the property for inspection and monitoring during review and construction, through to the Final Certificate of Zoning Compliance. Septic systems need at least 24 hours’ notice for inspection before backfilling, and an as-built record is required either way.
In Miles City, the person doing the work notifies the building official when it is ready for inspection.
Local details that matter
Zoning districts: the County uses 8 classifications: AG-1 Agricultural/Rural Residential, R-1 Single Family, R-2 Multi-Family, R-3 Modular Home, C-1 General Commercial, I-1 Industrial, P-1 Public and Planned Unit Development.
Where County zoning applies: the regulations adopted as Resolution 2016-31 describe the districts as covering the county outside Miles City and Ismay, and the County’s online zoning map draws a zoning boundary around Miles City. The Zoning Department (406-874-4024) confirms whether a parcel is zoned.
Zoning update: the Commissioners gave notice of a third public hearing, on October 7, 2026, on updated zoning regulations and an updated zoning map, and the County posts the 2026 update as a draft. Until it is adopted, the 2016 text and the posted fee schedule apply. The hearing notice says zoning districts and zoned areas are not being added or removed.
Fences: no fence in a residential district may be taller than 8 feet, and barbed or electrically charged fences are not allowed there.
Conditional uses: an applicant must ask for a pre-application meeting, which is scheduled within 15 days of the request. A conditional use permit expires if the use stops for 6 months.
Septic permits: a permit is void if the system is not installed within 24 months.
Miles City siding and mechanical permits: the City has required a siding permit since March 1, 2026 and a residential mechanical permit since July 1, 2026.
Miles City applications: the City treats a building permit application as abandoned 180 days after filing unless it has been pursued in good faith or a permit has been issued.
Montana building code
Montana adopts one building code, based on the 2024 International Codes from 26 September 2026; a certified local program or the state Building Codes Program enforces it, and the state code does not reach houses of fewer than five units, farm and ranch buildings or private garages unless a local government has made it apply to them. How Montana’s statewide code works
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These are the primary sources behind this guide. Codes, fee schedules and procedures change — confirm the position for your filing date.
- Montana effective construction code editions
- Montana certified local building programs
- Montana DLI state building permit application
- Custer County Environmental Health: wastewater permits and forms
- Custer County Land Use: zoning, planning and floodplain forms
- Custer County Zoning Regulations (Resolution 2016-31)
- Custer County zoning map
- Custer County Site Plan Review Application (2026)
- Custer County zoning fee schedule
- Custer County floodplain permit fees (Resolution 2026-21)
- Custer County wastewater treatment system application
- Miles City Building Department
- Miles City notice of March 1, 2026: siding and residential mechanical permits
- Montana certified local governments, printable list (updated October 7, 2026)
Inspections are where schedules slip.
Get a free quote →Custer County permit FAQs
Do I need a permit to build a house in Custer County?
On land in a County zoning district you need a County zoning conformance permit, with site plan review, before building; the County’s zoning map shows which parcels are zoned. The State does not require a building permit for a residential building with fewer than 5 units. Inside Miles City, the City’s Building Department issues the building permit.
How much is the County zoning permit?
Site plan review is $100 for a residential project and $200 for a commercial one on the County’s posted zoning fee schedule.
How long does site plan review take?
Up to 5 working days for the completeness check and up to 30 working days for a decision once the application is complete.
Do I need a permit for a shed or a fence?
An accessory structure under 100 square feet needs no zoning conformance permit if it meets the district standards. The County’s fee schedule lists a $25 fence permit, and inside Miles City the City’s fence permit form shows a $100 fee.
How much is a septic permit in Custer County?
$200 for a gravity system, $350 for a pressure dose system and $550 for a Level II system.
What does a floodplain permit cost?
$550 for a simple application and $950 for a complex one under Resolution 2026-21, rising to $800 and $1,200 when the work was done first.
Who issues electrical and mechanical permits in Miles City?
The Miles City Building Department issues electrical permits for residential buildings and, since July 1, 2026, residential mechanical permits. Commercial electrical work and plumbing are state permits.
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More Montana permitting guides
This guide is provided by Alliance Permitting for general information about Custer County permitting. Requirements, fees, and procedures change; confirm details with the permitting authority before relying on them.