stringpiece

A stringpiece is one of the two angled wooden members that run along the sides of a staircase, supporting the treads and risers. In a straight flight, each stringpiece is a single board or beam cut at an angle and notched or routed to receive the treads (the horizontal steps you walk on) and sometimes the risers (the vertical faces between steps). The stringpiece carries the weight of people descending or ascending, transferring that load down to the floor structure at both top and bottom.

There are two common types. A closed stringpiece (or housed stringer) has its treads and risers fully contained within routed grooves cut into its inner face, creating a neat, finished appearance and allowing the staircase to sit flush against a wall. An open stringpiece has notches cut into its upper edge so the treads sit on top and the ends of the treads and risers remain visible from the side. Open stringpieces are cheaper to produce and repair, but show more structural work.

Material and dimension

Stringpieces are typically milled from solid timber (pine, oak, or hardwoods depending on finish quality), or sometimes from laminated beams or engineered lumber in modern construction. A stringpiece for a domestic staircase is usually 1.5 inches to 2 inches thick and 10 to 12 inches deep, though dimensions vary with span and load. The board must be strong enough to resist deflection under foot traffic without visible sagging.

The term stringpiece also applies more broadly to any long horizontal or near-horizontal timber that forms the edge or boundary of a structural assembly, particularly in timber frame construction. In this wider sense, a stringpiece can frame the perimeter of a platform or walkway. The name derives from its function: it is the "string" or line that edges and supports the whole structure.