Unincorporated Yellowstone County building permits
VerifiedDepartment contacts, adopted codes, permit types, fees, and gotchas for Unincorporated Yellowstone County, Montana.
Last verified 2026-07-02 · Source
Building department
- Address
- 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
- buildingcodes@mt.gov
- Office hours
- Mon–Fri, state business hours; online permitting available 24/7 via https://aca-prod.accela.com/bcb/
- Website
- Official site
Codes adopted
Montana adopts a single statewide building code by rule and, by default, enforces it directly — local governments only gain enforcement authority once the state certifies them. Under the Montana Building Codes Act (Mont. Code Ann. Title 50, Chapter 60), the Department of Labor & Industry's Building Codes Bureau adopts one state building code applicable everywhere (§ 50-60-203, codified further at Administrative Rules of Montana Title 24, Chapter 301) — currently the 2021 editions of the IBC, IRC, IMC, IFGC, IECC, IEBC, ISPSC, and UPC, with the 2020 NEC for electrical (effective statewide since 6/11/2022 per the Bureau's own Current Codes page). A city, county, or town may adopt and enforce its own building-code program under § 50-60-301, but its adopted code "may include only codes adopted by the Building Codes Bureau" — a local edition can never diverge from or be less stringent than the state's. Critically, under § 50-60-302, a local government cannot enforce ANY building code — even one it has formally adopted — until the Bureau certifies its program (requiring an approved code, a published fee schedule, an enforcement plan, and properly licensed or nationally certified inspectors); certification is granted per TRADE, not as one blanket designation. The Bureau's own "Certified City, County and Town Programs" list uses the key B=Building, P=Plumbing, E=Electrical, M=Mechanical, SP=Pool, W=Wildland-Urban-Interface — a jurisdiction can be certified for Building only while Electrical/Plumbing/Mechanical remain directly state-enforced within the same city limits (e.g., Havre, Anaconda-Deer Lodge), or certified across all trades (e.g., Billings, Missoula, Great Falls, Bozeman, Helena, Kalispell). Non-certified jurisdictions — most of Montana's unincorporated county land, since very few counties appear on the certified list — fall under direct enforcement by the state Building Codes Bureau (§ 50-60-304). Montana also exempts private homes and buildings of four or fewer dwelling units not serving transient guests from the state building-permit requirement entirely, though electrical, plumbing, and mechanical permits remain separately required regardless. Always confirm with the specific jurisdiction which trades it is certified for versus which remain directly state-enforced.
Permit types & fees
Residential Building Permit
In unincorporated Yellowstone County, Yellowstone County itself issues NO building permits or Certificates of Occupancy — confirmed directly by the county: 'Yellowstone County does not issue Building Permits or Certificates of Occupancy for structures outside the city limits of Billings.' Building permit authority instead sits with the Montana Building Codes Bureau (state DLI), EXCEPT that Montana state law exempts private homes and apartment buildings of four or fewer dwelling units (that do not serve transient guests) from the state building permit requirement entirely. Practical effect: most single-family homes, duplexes, triplexes, and fourplexes built in unincorporated Yellowstone County require NO building permit from any government body — county or state — for the structure itself. A state building permit IS required for 5+ unit residential buildings and any non-exempt structure.
Electrical Permit
All electrical work in unincorporated Yellowstone County requires a State Electrical Permit from the Montana Building Codes Bureau, since Yellowstone County is not a certified local government for electrical code enforcement. Homeowners may wire their own home under a Homeowner Electrical Permit; all other work requires a Montana-licensed electrical contractor. Governed by Title 50, Chapter 60, Section 604, MCA and ARM 24.301.431.
Plumbing Permit
Plumbing work in unincorporated Yellowstone County is permitted directly by the Montana Building Codes Bureau under Title 50, Chapter 60, Section 505, MCA and ARM 24.301.301/24.301.361, since the county is not a certified local plumbing-code jurisdiction. A per-fixture fee schedule applies. Homeowners performing their own plumbing on their own owner-occupied, non-rental residence are exempt from needing a permit.
Mechanical / HVAC Permit
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.
Roofing Permit (Reroof)
Reroofing is listed as a 'Type of Work' option (Reroof) on the Montana state Application for Building Permit. Because most single-family and up-to-fourplex residential structures are exempt from the state building permit requirement in Montana (private homes/apartments with four or fewer units not serving transient guests), a straightforward residential re-roof on an exempt dwelling generally does NOT require a state building permit. Confirm applicability with the Building Codes Bureau for your specific structure.
Solar Panel Permit
Solar installations in unincorporated Yellowstone County are permitted through the Montana Building Codes Bureau's electrical/alternative-energy permitting track — there is no separate 'solar permit'; instead, the permit type depends on who performs the installation and whether it is grid-tied. The Bureau publishes a specific solar permitting decision flow for new residential construction.
Accessory Dwelling Unit (ADU)
Montana has no ADU-specific state permit type; an ADU in unincorporated Yellowstone County is permitted the same way as any other residential structure. Because the state building-permit exemption applies to 'private homes and apartments with four or fewer units,' a detached or internal ADU that brings the total unit count on the property to four or fewer generally does not require a state building permit for the structure itself — but its electrical, plumbing, and mechanical systems each require their own state permits regardless.
Water Heater Permit
Installing or replacing a water heater in unincorporated Yellowstone County requires a state plumbing permit line item from the Montana Building Codes Bureau, unless the owner-occupant exemption applies (homeowner doing the work themselves on their own non-rental, non-speculative residence).
New residential construction activity
New privately-owned residential construction onlyHousing units authorized by building permits for new privately-owned residential construction — this is not total permit volume (no commercial permits or remodels).
- Latest month (2026-05)
- 67units
59 buildings · $15.8M valuation
- Trailing 12 months
- 1,086units
12 of 12 months reported · #1 in Montana coverage by units
- Year to date (2026 YTD through 2026-05)
- 417units
367 buildings · $101M valuation
- Full year 2025
- 997units
781 buildings · $276.5M valuation
County-wide figures: BPS reports county-wide totals; jurisdiction is the unincorporated remainder outside the City of Billings — county totals (FIPS 30-111) include incorporated Billings plus smaller incorporated towns (Laurel, Broadview, Shepherd is unincorporated CDP). Unincorporated area building activity is not separately broken out by the Census Building Permits Survey; county FIPS confirmed via U.S. Census Bureau QuickFacts (census.gov/quickfacts URL path 30111) and the Census Bureau's TIGER state/county FIPS reference.
Source: U.S. Census Bureau, Building Permits Survey (BPS), 2026-05 vintage. Census survey data — separate from the permit-requirements verification above. All Montana building activity
Tips & gotchas
- Yellowstone County itself issues NO building, plumbing, mechanical, or electrical permits, and NO Certificates of Occupancy, for any structure outside the Billings city limits — confirmed directly on the county's own Public Works site and in the county's official 'Construction Outside of City Limits' notice.
- Because Yellowstone County has never established a certified local building-code enforcement program, all state-level codes (building, electrical, plumbing, mechanical) in the unincorporated county are enforced directly by the Montana Building Codes Bureau (DLI) — confirmed by Yellowstone County's absence from the Bureau's Certified City, County and Town Programs list, on which several other Montana counties (Deer Lodge, Missoula, Pondera, Richland, Toole) do appear.
- Montana state law exempts 'private homes and apartments with four or fewer units that do not serve transient guests' from the state building permit requirement entirely — meaning most single-family homes, duplexes, triplexes, and fourplexes in unincorporated Yellowstone County need NO building permit from any government body for the structure itself. This exemption does NOT extend to electrical, plumbing, or mechanical permits, which are still required from the state for each trade.
- Related contacts for development outside Billings city limits: City/County Planning Division for zoning compliance (406-247-8247); Riverstone Health Environmental Health Services for septic/well (406-256-2770); Yellowstone County Public Works for road access permits (406-256-2735); Montana Building Codes Bureau for state building/electrical/plumbing/mechanical permits (406-841-2056).
- All Montana Building Codes Bureau permit applications can be filed online at https://aca-prod.accela.com/bcb/ or mailed to Building Codes Bureau, PO Box 200517, Helena, MT 59620-0517.
- Montana's currently adopted codes (all effective June 11, 2022 unless noted): 2021 IBC, 2021 IRC, 2021 IEBC, ICC A117.1-2017, 2021 UPC, 2021 IMC, 2021 IFGC, 2020 NEC, 2021 IECC, 2021 ISPSC, 2021 WUIC.
- Ground snow load and wind load for unincorporated areas are not published as a single fixed value for Yellowstone County — the Building Codes Bureau directs applicants to the ASCE 7 Hazard Tool or to call (406) 841-2056 directly for site-specific values.
- A separate Yellowstone County Public Works road-approach permit ($75 residential / $150 commercial) is required for any new driveway or access connecting to a county road — this is unrelated to the state building/electrical/plumbing/mechanical permits and is issued by the county itself.