Montana — Code Adoption Summary
Adoption model: Statewide-mandatory via Administrative Rules of Montana (ARM) Title 24, Chapter 301 — the state amendment text (not the raw model code) IS the legally binding "Montana Building Code." Last verified: 2026-07-03 Confidence: verified Primary sources: MT Dept. of Labor & Industry, Building & Safety Div. — https://bsd.dli.mt.gov/building-codes-permits/current-codes · ICC MT
Statewide adopted codes — current (2026)
| Code family | Adopted edition | Effective | Source |
|---|---|---|---|
| Building / Residential / Existing / Mechanical / Fuel Gas | 2021 IBC/IRC/IEBC/IMC/IFGC (+ 2021 IWUIC wildland-urban interface) | 2023-03-11 | bsd.dli.mt.gov |
| Electrical (NEC) | NEC 2023 | 2023-09-23 | meltplan.com |
| Plumbing | UPC 2021 | Montana = UPC | bsd.dli.mt.gov |
| Energy | IECC 2021 + MT amendments | 2023-03-11 | " |
Pipeline: Montana plans to adopt the 2024 ICC family mid-2026 — check whether this has landed by the permit date. Structural note: Montana amendments/deletions/additions via ARM Title 24, Ch. 301 supersede the model-code text — always consult the ARM alongside the base IBC/IRC, not the base code alone.
Adoption model & precedence
- Codes are statewide-mandatory; the ARM amendment set is legally controlling where it conflicts with the base model code.
- AHJ = local building department, applying the statewide edition + ARM amendments.
Major cities / counties
| Jurisdiction | County | Notes | Building dept. |
|---|---|---|---|
| Billings | Yellowstone | statewide code | billingsmt.gov |
| Missoula | Missoula | statewide code | ci.missoula.mt.us |
| Bozeman | Gallatin | statewide code; publishes adopted-codes page | bozemanmt.gov |
AHJ fallback (when local adoption is unverified)
- State baseline (certain): 2021 IBC/IRC/IMC/IFGC, NEC 2023 (eff. 2023-09-23), UPC 2021, IECC 2021 + MT amendments.
- Action: confirm whether the 2024 ICC family (planned mid-2026 adoption) has taken effect for the permit date.
Change log
- 2026-07-03 — created; verified NEC 2023 (eff. 2023-09-23), 2021 I-Codes (eff. 2023-03-11), UPC 2021; flagged planned mid-2026 adoption of 2024 ICC family and ARM Title 24 Ch.301 as the controlling amendment structure.