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Clear depth at lowest step in assembly stepped aisles.

R

Redmund

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California
In an outdoor stadium seating setting that has stepped aisle, without any transition to/from regular stairs, what code section would give the required clearance between the face of the lowest step and the guardrail shown in the illustrative from the ICC commentary below?

1753828930033.png
 
Review CBC 1030. I just took a quick glance, and I'd say no, but don't take that to the bank.
 

"1030.13.2 ​

Where seating rows have 14 or fewer seats, the minimum clear aisle accessway width shall be not less than 12 inches (305 mm) measured as the clear horizontal distance from the back of the row ahead and the nearest projection of the row behind."

"1030.13.2.2 ​

For rows of seating served by an aisle or doorway at only one end of the row, the minimum clear width of 12 inches (305 mm) between rows shall be increased by 0.6 inch (15.2 mm) for every additional seat beyond seven seats where seats have backrests or beyond 10 where seats are without backrests. The minimum clear width is not required to exceed 22 inches (559 mm)."

While the question may be for the measurement from the face of the riser to the guard (for which I don't believe there is an answer), the width at this point is going to be same for the last step and aisle accessway at the guard. At least that is how I'm reading it and in any case, this would not have to exceed 22 inches for a single access design.
 
Thanks for the replies. I realized after posting that that markup of the drawing didn't really illustrate well. Please see this one below. It doesn't seem like the code has a specific clearance requirement for this.
View attachment 16097
 
I tried to add this to Redmund's post but it wouldn't work. So here it is.
Screenshot 2025-07-30 at 11-29-43 Stadium stepped aisle question.pdf.png
 
I think you can make a case for required aisle access way width. That is what I have used in lots of theatre balconies.

In the last sketch, I'd say that does not comply with IBC because of non uniform tread depth - 11s and 14s. Really should be three 12s - by IBC and ICC300 (and NFPA 101 and 5000 fwiw).
 
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