Arizona Building Codes: Local Adoption, No Statewide Residential Code

Arizona has no mandatory statewide residential building code. Cities and counties each adopt — and often amend — their own edition of the IRC. Phoenix, Tucson, and other municipalities run their own amended versions, on their own adoption timelines.

That means there’s no single “Arizona” figure for stair or guard geometry to cite here — it depends on which city or county you’re building in. As a starting point, the IRC baseline is what most Arizona jurisdictions build from — 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 (see the US stair & guard rules) — but confirm the adopted edition and any local amendments with your building department before relying on it.