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Stair Terminology and Common Building Codes

Stairs come in many different forms, and while building a basic staircase may appear to be a simple task, there are actually a number of parameters, calculations, and building codes that must be considered. Below is a list of some of the most common terminology regarding stairs, as well as general building codes. Building codes or requirements can differ at a local level, so refer to the codes specific to your location.

Run / Tread

The run or tread is the horizontal part of the stairway that a person steps on. Its length is measured from the outer edge of the step (including the nosing, if present) to the vertical portion of the stair called the riser. When measuring the total run of a staircase, the length of the tread above the last riser is not included. Also, when nosing is present, the total run is not simply the sum of tread length, since the overhang caused by the nosing must be subtracted from the total run.

Building codes generally suggest that the tread has a minimum length of 10 inches (25.4 cm).

Rise / Riser

The rise, or height of a step, is measured from the top of one tread to the top of the next tread. It is not the physical height of the riser board because the rise includes the thickness of the tread. The number of risers, not the number of treads, is used to determine the total number of steps that comprise a staircase.

Building codes generally suggest that the maximum height of a riser be 7.75 inches (19.7 cm).

Nosing

The nosing is the protrusion at the edge of a tread that hangs over the riser below. The main purpose of nosing is to improve safety by providing extra space on which a person can place their feet.

Common building codes generally suggest that the nosing has a minimum length of 0.75 inches (1.9 cm) and a maximum length of 1.25 inches (3.2 cm).

Headroom

Headroom is the height measured vertically from the top of a tread to the ceiling above it. Codes typically require far more room than the average height of a person to allow for moving larger objects such as furniture.

Building codes generally suggest at least 6 ft. 8 inches (203.2 cm) of stair headroom.

Stair Width

Stair width is measured from edge to edge of each side of the tread, perpendicular to the tread length. Stair width does not include handrails.

Building codes generally suggest that stairs be at least 36 inches (91.4 cm) wide.

Handrails & Guards

A handrail is a railing that runs up a stair incline for users to hold when ascending or descending. A guard is a building component located near open sides of elevated surfaces that minimizes the possibility of a fall.

Building codes generally require guards for stairs that have a total rise of more than 30 inches, and require that these guards be at least 34 inches (86.3 cm) in height. Handrails must be between 34 and 38 inches high measured from the top of the treads.

Stringer

A stair stringer is the structural member that supports the treads and risers of a staircase. Typically, there are three in a staircase: one on each side, and one in the middle. The stringers can either be cut to the shape of each step (cut stringer), or be uncut, concealing the edges of the treads (closed stringer).

Fraction to Decimal Conversion Chart

When measuring and cutting wood for stairs, you will frequently need to convert fractions of an inch into decimals.