Montana Building Code: Which Editions Are Adopted

Direct answer

Montana's adopted code editions, as recorded in the ICC Master I-Code Adoption Chart (January 2024): 2021 IBC, 2021 IRC, 2021 IECC and 2021 IFC. The chart gives an edition year for 11 of the 17 I-Codes it tracks in Montana; the remainder are either adopted only by individual agencies, replaced by a state-written code, or not adopted at all. A chart entry is not an effective date and it is not the amended text. ICC records adoptions as jurisdictions report them, so a state that moved edition after January 2024 will still show the older year here. Confirm both the edition and its effective date at Montana Department of Labor and Industry, then read the state amendments, because an amended definition or table changes the requirement even when the edition matches.

Content and cited inputs reviewed by Scott Barrington, Harth founder and architectural technology specialist · Published 2026-09-07 · Updated 2026-09-07.

What must be verified before using this guidance?

Every I-Code the ICC Master I-Code Adoption Chart (January 2024) tracks, as it records Montana:

Montana has a recorded edition year for 11 of the 17 codes: 2021 for the building, residential, fire, mechanical, fuel gas, green construction, residential energy, commercial energy, existing buildings, swimming pool and spa and wildland-urban interface codes. No adoption at all is recorded for the plumbing, private sewage, property maintenance, performance, zoning and green building standard codes.

Source: ICC Master I-Code Adoption Chart (January 2024).

How Montana compares with its neighbours

Idaho differs from Montana on the building code alone. A practice working across that border is working to two editions, whatever the office standard says.

Where Montana sits in the national record

Of the 50 states and the District of Columbia, 18 are recorded on the 2021 IBC, 0 on a later edition, 26 on an earlier one, and 7 with no statewide IBC edition at all. Montana is at or ahead of the national middle on the building code, so the risk runs the other way: work arriving from a slower-moving state may be drawn to an older edition.

The building code and the residential energy code are on the same 2021 edition here. That is convenient but not a rule — the two are adopted under separate processes and can diverge at the next cycle.

Across all 17 codes the chart tracks, Montana has a recorded edition for 11, which ranks it 3rd of 51. A low count is not a gap in regulation — it usually means the state legislates through its own documents, or leaves the discipline to local adoption.

What the chart does and does not tell you

The chart's own legend matters more than the numbers:

• An edition year means one or more state or local agencies adopted that edition. It does not mean every building in the state is designed to it.
• “Some jurisdictions only” is the chart's X: the code is in use somewhere in the state but is not the standard for all buildings.
• “Not adopted” is a blank cell — no state or local jurisdiction reported adopting that code.
• “State-written code” means the state publishes its own document in place of the model edition, so the model text is a reference, not the law.

ICC states plainly that not every jurisdiction notifies it of an adoption, and this chart is dated January 2024. Treat it as the starting point for a search, never as the answer.

How to confirm the edition that governs a Montana project

1. Open Montana Department of Labor and Industry and find the currently adopted code list with its effective date.
2. Check whether the permit authority for the project address is the state or a local programme with its own adoption.
3. Read the state amendments alongside the model edition — an amended table or definition changes the requirement even when the edition matches.
4. Record the permit application date. A code change usually applies from an effective date, and applications filed before it are normally reviewed under the previous edition.
5. Get the answer in writing from the authority having jurisdiction before it drives a design decision.

This site also hosts a transcription of the 2009 model code chapters as adopted in Montana at /building-codes/us-states/montana. That is a historical reference for the 2009 editions and is not Montana's current code basis.

Montana code-basis worksheet

Fill this in once per project and keep it with the drawing set. Every row is a question a plan reviewer can ask, and the answer changes with the address and the application date, not with the state.

This worksheet records a determination; it does not make one. The authority having jurisdiction decides which edition and which amendments apply.

Where can you explore related guidance?

• Explore all code adoption guidance
• Idaho Building Code: Which Editions Are Adopted
• Wyoming Building Code: Which Editions Are Adopted
• North Dakota Building Code: Which Editions Are Adopted
• South Dakota Building Code: Which Editions Are Adopted

Sources and method

Adopted editions transcribed from the ICC Master I-Code Adoption Chart (January 2024), reproduced with the chart's own legend so an “X” is not mistaken for a statewide adoption. ICC notes that not all jurisdictions report their adoptions and publishes updates at iccsafe.org/adoptions. The current edition, its effective date and the state amendments are published by Montana Department of Labor and Industry, which controls.

Source links

• iccsafe.org

• iccsafe.org

• bsd.dli.mt.gov