A Short Guide to Understanding Stairs
This article is intended to be an aid for the description of pedestrian stair incidents.
A stair is a pedestrian walking route to accomplish vertical access between a change in elevation. As defined in the International Building Code, a stair can even be a single riser. Here are some of the basic definitions:
Tread: The flat-horizontal depth of the stepping surface, which is measured from a riser to the outboard edge of the tread nosing.
Nosing: The tread outboard edge, usually projected forward beyond the riser below the tread.
Effective Tread Depth: The measurement of horizontal depth that is measured from nosing to nosing. You might think of this as the useable depth of the tread.
Riser: The vertical height measured from top of tread to the top of an adjacent higher or lower tread, floor, or landing.
Landing: The horizontal platform at the end of a stair flight or between two flights of stairs.
Stair Run: One stair flight between landings.
Stairway: A flight or multiple flights of stairs between floors.
Stair Well: An enclosed stair, generally for fire rating.
Handrail: A handhold that is graspable by a power grip, is continuously graspable prior to commencing ascent/descent and remains graspable without needing to release grip until ascent/descent travel is completed. Handrail shapes and dimensions graspable by a power grip are defined in the International Building Code.
Handrails are safety devices. Handrail should have the strength to resist an applied load of 200 pounds, which may be applied at any location and in any direction. Handrails serve to guide persons in ascent and descent, they provide a tool for the user to exert stabilizing forces, they provide for pulling when arms are used to augment legs in ascent and they are a tool that can be utilized to help in the arrest of a fall
Guard: A barrier or protection from falling from an open side or stairwell perimeter.
Pedestrian: Generally, stairs constructed in compliance with the International Building Code are intended to dimensionally accommodate the 95-percentile male. The mass of an ambulating pedestrian is somewhat centered about the torso. During forward travel the pedestrian’s mass, unless unbalanced, is shifted forward. Therefore, falls on stair related to a trip type event are forward. However, a loss of balance due to a slip or misstep can result in a forward or backward fall.
When a handrail is being used, the grasping hand is generally forward from the pedestrian, and therefore, if handrail failure occurs and results in a loss of support it can cause a forward fall. Alternately, a handrail failure can cause a loss of balance that results in a backward fall.
The following can assist in relating the pedestrian’s use of the stair to the stair geometry:
- Where stature may be an issue: For a taller person establish height (for anthropometric data), weight, and shoe size.
- Was the handrail within reachable grasp?
- Was there difficulty ambulating the stair?
- Where along the stair run did the incident occur?
- Were the tread nosings discernible?
- What was the finish material of treads and risers?
If the treads were carpeted, was the carpet loose, frayed, or torn?
For the tread nosings – Define the material and condition. - Was illumination an issue?
- Was a foreign substance on a tread an issue? Describe this foreign substance for color and consistency.
Dependent upon the incident circumstances, there may be additional or different questions to have answered. Your expert can assist you in obtaining the best information available for their analysis of the incident.
Feel free to contact us to speak with Mr. Cohen or one of our other experts in regard to slip, trips, and falls on any number of surfaces.