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Mechanical / HVAC Permit in Unincorporated Yellowstone County, Montana

HVAC, 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

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Fee schedule

Mechanical system cost $0–$10,000Montana 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.
$48 for the first $1,000 + $14 for each additional $1,000 or fraction thereof
Mechanical system cost $10,001–$50,000Same source
$166 for the first $10,000 + $9 for each additional $1,000 or fraction thereof
Mechanical system cost $50,001 or moreSame source
$514 for the first $50,000 + $6 for each additional $1,000 or fraction thereof

Review timeline

Plan reviewTypical estimate — confirm current times with the Unincorporated Yellowstone County building department
~1–5 business days

How long did your Mechanical / HVAC Permit permit actually take in Unincorporated Yellowstone County?

Anonymous — one question, no email. Answers are combined and only shown once at least 5 people have reported.

Inspection process

    See the full Unincorporated Yellowstone County inspection guide — scheduling & re-inspection fees →

    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

    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.

    In Unincorporated Yellowstone County, the published Mechanical system cost $0–$10,000 is: $48 for the first $1,000 + $14 for each additional $1,000 or fraction thereof. Additional published fees: Mechanical system cost $10,001–$50,000 — $166 for the first $10,000 + $9 for each additional $1,000 or fraction thereof; Mechanical system cost $50,001 or more — $514 for the first $50,000 + $6 for each additional $1,000 or fraction thereof. These are the jurisdiction's own published figures — see the fee schedule table and source citations on this page.

    Plan review for a mechanical / hvac permit in Unincorporated Yellowstone County typically runs 1–5 business days. This is an estimate, not a published figure — confirm current review times with Montana Department of Labor & Industry — Building Codes Bureau (Business Standards Division, Building and Commercial Measurements Bureau) at (406) 841-2056.

    You'll need: Application for Mechanical Permit (BCP-1). See the required-documents checklist on this page for details on each.

    Apply through Montana Department of Labor & Industry — Building Codes Bureau (Business Standards Division, Building and Commercial Measurements Bureau) at 301 South Park Ave, Floors 4-5, Helena, MT 59620 (mailing: Building Codes Bureau, PO Box 200517, Helena, MT 59620-0517). Phone: (406) 841-2056, email: buildingcodes@mt.gov. Office hours: Mon–Fri, state business hours; online permitting available 24/7 via https://aca-prod.accela.com/bcb/. Official information: https://bsd.dli.mt.gov/building-codes-permits/.

    Unincorporated Yellowstone County, Montana has adopted: 2021 International Building Code (IBC) — adopted statewide by ARM Title 24, Chapter 301; effective June 11, 2022; 2021 International Residential Code (IRC) — ARM Title 24, Chapter 301; effective June 11, 2022; 2021 International Existing Building Code (IEBC) — ARM Title 24, Chapter 301; effective June 11, 2022; ICC A117.1-2017 (Accessibility) — ARM Title 24, Chapter 301; effective June 11, 2022; 2021 Uniform Plumbing Code (UPC) — ARM Title 24, Chapter 301; effective June 11, 2022 (fixture table at ARM 24.301.351); 2021 International Mechanical Code (IMC) — ARM Title 24, Chapter 301; effective June 11, 2022; 2021 International Fuel Gas Code (IFGC) — ARM Title 24, Chapter 301; effective June 11, 2022; 2020 National Electrical Code (NEC) — ARM Title 24, Chapter 301; effective June 11, 2022 (NEC Technical Advisory NEC_TIA-23-3_210.8 issued August 12, 2022); 2021 International Energy Conservation Code (IECC) — ARM Title 24, Chapter 301; effective June 11, 2022; 2021 International Swimming Pool and Spa Code (ISPSC) — ARM Title 24, Chapter 301; effective June 11, 2022; 2021 Wildland Urban Interface Code (WUIC) — ARM Title 24, Chapter 301; effective June 11, 2022; NOTE: All codes listed are statewide codes administered directly by the Montana Building Codes Bureau for areas (like unincorporated Yellowstone County) that are NOT within a certified local-government building code jurisdiction..

    Sources & verification

    Verified against official sources. Last reviewed 2026-07-02.

    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.

    Other permits in Unincorporated Yellowstone County

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    Mechanical / HVAC Permit in other cities

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