IBC stair width vs ADA stair width



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    Derek Newman

    I believe the 48" ADA clearance is for the area of refuge.



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    Elizabeth Lagarde

    Hi Frank, 

    I did not see the required minimum width in the 2010 ADAS or ANSI A117.1. However, it is mentioned in the  IBC. For a Stairway to be considered as an accessible means of egress, the stairway shall have a clear width of 48" minimum between handrails (IBC 1009.3.2).

    Also, I want to add to this point:

    • "IBC states that the minimum stair width is 44"."

    This is true but not always the case. The stair width sizing should be determined first as specified in 1005.3.1: The capacity, in inches, of means of egress stairways, shall be calculated by multiplying the occupant load served by such stairways by a means of egress capacity factor of 0.3 inch per occupant.

    For example, if the stairway serves an occupant load of 155, then 155 x 0.3 = 46.5 inches. Now your minimum is 46.5", not 44".

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