Montana Building Codes in 2026: Editions, Dates and AHJ

Direct answer and reference scope

Montana Building Codes in 2026: Editions, Dates and AHJ is a Harth adoption and amendment guide for Montana. Montana's current 2021 I-Codes, June 2022 effective date, 2017 accessibility standard, 2019 elevator code and local-enforcement checks. Use the Montana Department of Labor and Industry to confirm the code edition currently adopted for the project, and compare the model text with state amendments, local amendments, effective dates and the permit authority's interpretation. The ICC code library is the model-code publication path. This Harth page summarizes adoption records and amendment sources; it does not reproduce the controlling code, provide a legal opinion or confirm which edition controls a particular address. Record the project jurisdiction, application date, occupancy, construction type and amendment set before relying on a section. Where this page conflicts with an official publication or the authority having jurisdiction, the official source controls.

Authored and prepared by Harth from the linked agency records. Review scope: adoption status and source paths verified; project-specific applicability and local interpretation require AHJ confirmation.

Direct answer

Montana currently uses the 2021 International Building, Residential, Existing Building, Energy Conservation, Mechanical and Fuel Gas Codes, all effective June 11, 2022 and amended through Administrative Rules of Montana Title 24, Chapter 301. Montana uses the 2021 Uniform Plumbing Code, 2020 NEC, ICC A117.1-2017 and ASME A17.1-2019 on the same current-code list.

Montana published proposed 2024-edition amendments in 2026, but the proposal is not treated here as adopted law. Use the Department of Labor and Industry’s current-code page and final rule notice to identify when a new edition actually takes effect.

Current Montana code matrix

Source: Montana DLI, Current Codes. Every listed code is subject to Montana amendments in ARM Title 24, Chapter 301.

State or local enforcement?

Montana’s Building Codes Program adopts the uniform state code and directly serves areas without a certified local program. Cities, counties and towns can operate certified building, electrical, plumbing and mechanical enforcement programs, but their adopted codes must stay within the state framework. State-owned agency projects remain with the state program.

For each project, record:

1. whether the address is served by a certified local enforcement program;
2. the state and local amendment set;
3. the permit-application date and any transition rule;
4. the building official’s snow-load determination; and
5. discipline-specific permits handled by the state rather than the locality.

Montana code-basis worksheet

The legacy 2009 energy-code material linked below is retained as a historical reference. It is not Montana’s current 2026 code basis.