Stair Rise & Run Rules

Uniformity

• The steps of a set of stairs must be uniform in size and configuration. This is important for the safety of people using the stairs. People moving on stairs develop a cadence or feel for the stairs. Steps of a different size disrupt the cadence and can cause falls or stumbles.

Rules of the Rise

• The basic rule for the rise of a step limits the height to 8 1/4 inches. There are no minimum rule for the height of the rise. The amount of rise of each step is determined by the total rise, the distance between the two levels of the building, and the number of steps to the stairway.

Rules of the Run

• The rule about the run of each step is a bit more complex. The minimum distance for the run is 9 1/4 inches and is measured from the front of the stair tread to the back of the step if there is no overhang from the tread of the step above. If the tread overhangs the step below the point directly below the front of the tread is used as the back measuring point for the run of the step.

Calculating the Stairs

• Calculating the rise and run of a set of stairs is a exercise in mathematics. The total rise is the distance between the finished floor levels of each level of the building. There must be enough steps to produce a rise of no more than 8 1/4 inches. The total run is the horizontal distance between the opening at the upper level and the point where the stairs will end at the lower level. This total run is divided by the number of steps to determine the run that must fit the rules of a run.