Montana Residential Code: Stairs & Guards

Montana builds to the Montana Residential Code — the 2021 IRC incorporated by reference statewide (ARM 24.301.154), mandatory across the state. It was first adopted in 2022 and re-adopted effective 21 September 2024.

For a house stair, the figures match the IRC baseline — 7¾ in max riser, 10 in min tread, 6 ft 8 in headroom, 36 in min width, 34–38 in handrails, 36 in guards, the 30 in guard trigger and the 4 in sphere. No Montana-specific stair or guard amendment has been confirmed. See the US stair & guard rules for the shared figures, and confirm against the current ARM text for any local amendments.