Stringer
Staircases rely on a stringer to support the steps, but you might or might not see it
A staircase rises vertically on a diagonal, creating an elevation change that is manageable in a series of steps. The steps, or treads, are supported by one or two stringers. Traditionally stringers are hidden in a closed system, but in modern design, the stringer can be a striking feature worthy of display.
The stringer is the support for the steps of a staircase. This outer stringer is cut in a zigzag pattern to accommodate the flat treads and vertical risers.
These steel beam stringers are not cut, and an open-tread staircase was created with steps suspended between the stringers with brackets and bolts.
In traditional staircase design, stringers are in a closed system, meaning hidden from view. This staircase has frame and panel millwork that contains the structural parts of the staircase.
Typically the stringer is cut to provide a base for each step, or tread. Steps need to be perfectly equal in height; even a 1/4-inch difference can cause trips and falls.
A single stringer is the only support for this floating staircase; the structural part of the staircase is the showcase.
When creating stringers, the challenge for the carpenter is doing the math to create steps that are equal in height (rise) and travel on a diagonal (run).