A spiral stair is typically described as a stair with a circular plan having uniform treads that radiate from and wind around a common central post or supporting column.
In the context of the Code, the term “spiral stair” is used to describe any stair where: a) the plan of the treads forms part or all of the circle, b) the maximum stair width and tread depth are less than those required for curved stairs, and c) the maximum riser height is greater than that permitted in all other stair configurations.
