Short definition
A pie-shaped stair step that turns a corner — wider on one side than the other, common on quarter-turn or half-turn staircases. Wastes more material than a straight tread.
A stair winder is a step that turns a staircase corner. Unlike a straight tread (a rectangle of the same depth across the full stair width), a winder is wedge-shaped: wider at the outside of the turn and narrower at the inside. A quarter-turn staircase typically uses three winders to make the 90-degree turn; a half-turn uses six.
Winders waste more carpet and vinyl than straight treads because the wedge shape is cut from a rectangle of material and the off-cut is rarely large enough to reuse. A straight residential tread might be 1.0 × 0.3 m (0.3 m²); a winder of the same depth wastes 30-50% more material depending on the wedge angle.
In a stair takeoff, the convention is to count winders separately from straight treads and apply a higher wastage figure to the winder count. Some estimators quote each winder as the equivalent of 1.5 straight treads of the same width — a useful rule of thumb when a customer asks for a rough number on the phone before a real takeoff.
The other consideration is install labour: winders take longer to cut and fit than straights, and a job heavy on winders should reflect that in the labour line on the quote, not just the materials.
Quote from a flooring estimator
"There is straightforward stairs but then you have got winders. How many winders you have and how many straights — probably the two biggest things you need on a stair takeoff."