Under the Massachusetts State Building Code, 780 CMR, the width of a stairway is typically measured from outside stringer to outside stringer. Stairways are required to have a minimum width of 44”. Handrails are permitted to project into the required minimum width by a maximum of 4 ½” on each side of the stair.
If a floor has a total occupant load of less than 50 people, the minimum width of a stairway can be reduced to 36”.
In non-sprinklered buildings, stairways serving as an accessible means of egress are required to provide a minimum width of 48” between the handrails. Additionally, exterior stairs serving as a means of egress for an exterior area for assisted rescue are also required to provide a minimum width of 48”’ between handrails.
Have questions on how this affects your design? Contact us with questions regarding minimum stair widths!