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Stairway Accidents and Dimensional Uniformity

by Zoe Gaik

Architectural Forensic Associate

RGA Design Forensics

Over the years, tread surfaces can become worn, and though imperceptible at eye level, could cause there to be dips in the stair treads that result in deviations in stair riser uniformity. According to the National Fire Protection Association (NFPA), fire exit stairway risers and treads should be uniform and not deviate any more than 3/16 of an inch from the one below or above it (NFPA

Also, these wear patterns could cause excessive slopes of more than 1 in 48, or roughly two percent. This is also a code violation.

Although 3/16th of an inch and slopes exceeding two percent on stair treads may not seem like a lot, these deficiencies can lead to loss of balance and stairway accidents.

In once case we had recently at a large sports venue, the venue had a similar issue. What we thought was a simple slip and fall was really a dimensional uniformity and slope issue. A patron of the sports game had spilled a drink on an egress stair, yet while the incident step wasn't overly slippery when wet (as gleaned from a coefficient of friction test later on), the step bore a tread with a 6.3% slope and a riser that deviated 1/4th of an inch from the previous step. These findings ultimately were the crux of our report. Sustaining dimensional uniformity is important.

Please visit or give us a call to talk about the specifics of your case at (813) 226-2220.


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