Mechanical / HVAC Permit in Unincorporated Yellowstone County, Montana
VerifiedHVAC, furnace, gas piping, and other mechanical work in unincorporated Yellowstone County requires a State Mechanical Permit from the Montana Building Codes Bureau under Title 50, Chapter 60, Section 104, MCA and ARM 24.301.172, since the county is not a certified local mechanical-code jurisdiction. The fee is calculated from the total cost of the mechanical system installed.
Verified 2026-07-02 · Source
When you need this permit
- Required for forced air furnaces, air handling units, ventilation systems, refrigeration/cooling equipment, gas piping of any type, mechanical exhaust systems, and similar mechanical work
- State mechanical permits apply on all buildings to which state building permits are applicable, and in areas located outside cities certified to issue their own mechanical permits (unincorporated Yellowstone County qualifies)
- Permit fee is based on total cost of the mechanical system being installed
Required documents
- Required
Application for Mechanical Permit (BCP-1)
Signed by the mechanical contractor performing the work; filed with the Building Codes Bureau, PO Box 200517, Helena, MT 59620-0517, or online at aca-prod.accela.com/bcb. Requires 17-digit geocode, parcel number, and section/township/range.
Fee schedule
| Fee type | Amount | Notes |
|---|---|---|
| Mechanical system cost $0–$10,000 | $48 for the first $1,000 + $14 for each additional $1,000 or fraction thereof | Montana Building Codes Bureau, Application for Mechanical Permit (ARM 24.301.172, Rev. 11/25) — verbatim fee schedule. Example given: a $9,460 project = $48 + (9 × $14) = $174 total. |
| Mechanical system cost $10,001–$50,000 | $166 for the first $10,000 + $9 for each additional $1,000 or fraction thereof | Same source |
| Mechanical system cost $50,001 or more | $514 for the first $50,000 + $6 for each additional $1,000 or fraction thereof | Same source |
Review timeline
~1–5 business days
Typical estimate — confirm current times with the Unincorporated Yellowstone County building department
Inspection process
Tips
- The mechanical permit fee is calculated directly from the cost of the mechanical system, not a flat per-appliance fee — get a contractor quote for the full installed cost before applying so the fee can be calculated correctly.
- Gas piping of any type is included under the mechanical permit, not the plumbing permit, in Montana's state permitting scheme.
- Montana adopted the 2021 International Mechanical Code and 2021 International Fuel Gas Code, both effective June 11, 2022.
Frequently asked questions
- Do I need a permit to replace my furnace in unincorporated Yellowstone County?
- Yes. A State Mechanical Permit from the Montana Building Codes Bureau is required. The fee is calculated from the installed cost of the system: $48 for the first $1,000 plus $14 per additional $1,000 (or fraction) up to $10,000, with lower marginal rates above that.
Sources & verification
Verified against official sources. Last reviewed 2026-07-02.
- Montana Department of Labor & Industry — Building Codes Bureau (Business Standards Division, Building and Commercial Measurements Bureau) — official building department
- Montana Building Codes Bureau — Mechanical Permits (requirements, jurisdiction)
- Montana Building Codes Bureau — Application for Mechanical Permit (ARM 24.301.172, Rev. 11/25) — verbatim fee schedule
Fees, timelines, and adopted codes are researched from each jurisdiction's published records — see how we verify. Requirements change and vary by project, so always confirm the current details with the Unincorporated Yellowstone County building department before you submit. PermitBase is an independent reference and is not affiliated with any government agency.
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