Clear Stair Width - Building And Safety Codes
To the best of my knowledge, the clear stair width
represents the overall width of a stairway.
In the example above, without walls, it would represent the over all width and for the example below would represent the measurement between finished walls.
Reference: 2012 International Building Code - 1003.3.3 pages 240
However, handrails are allowed to protrude a maximum of 4 1/2 inches into the clear space area, but there is at least one exception
Reference: 2012 International Building Code - 1007.3 pages 244
This particular building code states that in order to be part of an accessible means of egress, the stairway shall have a clear width of 48 inches in between handrails, not in between walls or and including the overall width of the stairway, with a few exceptions and one of those exceptions will be for most residential dwellings or homes.
The clear width of a stairway for most residential buildings will be the actual width of the stairway and not the measurement in between protruding handrails that aren't protruding more than 4 1/2 inches into the clear space.
I don't mean to confuse you, but these building codes are confusing and difficult to interpret correctly for every situation, occupancy and building type.
Attention: Don't forget to check with your local building department to verify any building codes on this website. This information could be incorrect or outdated. Building codes are updated regularly and to some building departments have different interpretations for certain building codes.