What is the term for a long piece of 2x timber that supports a stair?

The correct term for a long piece of 2x timber that supports a stair is "stringer." Stringers are integral to stair construction as they provide the structural framework that supports the treads (the flat horizontal surfaces) and risers (the vertical portions between each step). They are typically cut to accommodate the angles and dimensions of the stairs, which allows for stability and proper alignment.

Stringers are usually made from 2x lumber, and their design is crucial in determining the overall strength and safety of the staircase. This makes them essential components in both residential and commercial stair construction. Identifying stringers correctly ensures that construction practices maintain safety standards and structural integrity.