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Stairs Calc

Winder

A wedge-shaped tread that turns a staircase without a flat landing.

A winder is a triangular or kite-shaped tread that lets a staircase change direction without a full landing, saving floor space in an L-shaped or U-shaped run. Because winders are wider on the outside than the inside, code controls their depth at the walkline. Example: a 90° quarter-turn made with three winders spreads the turn over three steps instead of one landing, fitting a tighter footprint. The IRC requires at least a 10 in run at the walkline, at least 6 in at the narrow end, and the same riser height as the straight flight. Winders are space-savers but trickier to climb than a landing turn.

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Related terms

Walkline The path 12 in in from the inside of a turn, where winder tread depth is measured. L-shaped stairs A staircase with a 90° turn, made with a quarter landing or winders. Landing A flat platform that breaks a flight or changes its direction. Spiral staircase A helical stair whose wedge treads wind around a central column. Kite winder The central, kite-shaped winder tread at a 90° turn made of three winders.

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L‑Shaped & U‑Shaped Staircase Calculator Design quarter‑turn (L), half‑turn (U) and winder stairs — Stairs Calc sizes each flight, lays out the turn, and checks winder treads at the walkline.
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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.