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Stairs Calc

Guardrail (guard)

The barrier protecting an open edge; minimum 36 in high (IRC residential).

A guardrail, or guard, is the protective barrier along any open side of a stair, landing, or balcony where the drop exceeds 30 in (762 mm). It stops people and objects falling off the edge. The IRC requires residential guards at least 36 in (914 mm) high; the IBC raises commercial guards to 42 in (1067 mm). Its infill — usually balusters — must reject a 4 in (102 mm) sphere. Example: an open-sided staircase needs a guard along its full run plus the upper landing. The handrail is the part you grip; the guard is the fall barrier behind it, and on stairs a single assembly often serves both roles at the proper heights.

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Related terms

Handrail The graspable rail along a stair; code height 34–38 in above the nosing line. Baluster (spindle) The vertical infill posts of a railing; gaps must reject a 4 in sphere. Glass railing A guard infilled with tempered glass panels instead of balusters. Cable railing A guard infilled with tensioned horizontal cables instead of balusters. Landing A flat platform that breaks a flight or changes its direction. Stair width The clear walking width of the flight; IRC minimum 36 in above the handrail.

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Baluster Spacing Calculator Enter your railing length and spindle width to get the number of balusters, the exact even gap and center‑to‑center spacing — checked against your code’s 4‑inch sphere rule.
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Written by the Stairs Calc editorial team. Methodology and code references: see our methodology.

Built and maintained by builders, drafters and engineers who plan stairs for a living — every code limit is transcribed from the published standard and cited to its exact section.

Last reviewed 2026-06-20 against IRC 2021/2024

Stairs Calc gives accurate geometry and checks it against published building-code limits, but results are estimates for planning. Codes are adopted and amended locally and change over time. Always confirm dimensions against your local adopted code and a licensed professional before you build.