Tread Flaring — Overview for Curved Stairs — Glossary entry

Tread flaring is the adjustment of tread goings in the curved section of a staircase so that the treads along the walking line have a uniform width. Because steps on the outer edge of a curve sweep a larger radius than those on the inner side, they would be uneven in width if spaced at equal angles. Flaring rotates the treads against each other and distributes them so the walking zone produces a natural stride rhythm. Flaring methods fall into mathematical (calculation-based) and graphical procedures – among them the angle method, ratio method, large-circle method, baseline flaring and the batten method. In modern stair design software, flaring runs automatically in the background.