What are wedge-shaped radiating treads on stairs called?

Wedge-shaped radiating treads on stairs are referred to as winders. Winder treads are specifically designed to create a turning space on the staircase where the stairs change direction. This design is important for maintaining a comfortable and safe transition when ascending or descending around corners.

Unlike standard treads, which are typically rectangular, winders narrow at one end and widen at the other, allowing for a smoother curvature. This shape helps maximize the usable space in areas where a straight run of steps would be impractical due to the layout of the building.

The other terms are related to stair construction but do not specifically describe the radiating treads. For example, landings are flat areas between flights of stairs; treads are the horizontal surfaces where you step; and risers are the vertical components that connect one tread to the next. Each of these plays a role in the overall structure and design of stairways, but they do not define the wedge-shaped design characteristic of winders.