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Stairs Calc

Kite winder

The central, kite-shaped winder tread at a 90° turn made of three winders.

A kite winder is the middle tread in a three-step 90° turn, named for its diamond or kite plan shape — its two outer edges are equal and it sits symmetrically across the corner, flanked by two more triangular winders. Splitting a quarter-turn into three winders instead of one wide tread keeps each step climbable. Example: in a typical L-shaped winder set, the first and third treads sweep 30° each and the kite winder takes the central 30°, totalling the 90° turn. Like any winder, code measures its depth at the walkline — the IRC wants at least a 10 in (254 mm) run there and never less than 6 in at the narrow end. The kite winder is the trickiest tread to climb, so its walkline depth is the one to check first.

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Related terms

Winder A wedge-shaped tread that turns a staircase without a flat landing. L-shaped stairs A staircase with a 90° turn, made with a quarter landing or winders. Walkline The path 12 in in from the inside of a turn, where winder tread depth is measured. Run (going) The horizontal depth of one step, measured nosing-to-nosing, not counting the overhang.

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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.