Iowa Building Codes: Local Option, No Statewide Residential Code

Iowa’s state building code residential provisions are based on the 2015 IRC, but for new one- and two-family dwellings, adoption is a local option under Iowa Code Chapter 103A — a jurisdiction can adopt the state provisions, a different edition, or effectively no residential building code at all. The statewide-mandatory pieces are chiefly the energy code, not the structural/life-safety provisions.

Because adoption is local, there’s no single “Iowa” figure for stair or guard geometry to cite. As a starting point, the IRC baseline is what Iowa’s 2015-IRC-based provisions 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 what your local jurisdiction has actually adopted before relying on it.