This is the most popular spiral stair size today. According to most building codes (IRC, BOCA, UBC etc.) spiral stairs must have at least 26″ clear step space. These stairs can meet the MINIMUM required dimension for spiral stairs that serve as a secondary means of egress to a living space. All of our spiral stairs can be made to meet other components of code requirements (such as; head room, riser height, baluster spacing, etc.) but Acadia Stairs 60″ diameter spiral stair is the smallest spiral staircase that will meet the 26″ clear space requirement. This is a comfortable stair that gives enough clearance to bring a laundry basket, groceries, school books etc. up & down much more easily than smaller spiral staircases. In order to guarantee proper handrail clearance in tight stairwells, please make the finished opening 1.5″ larger in radius (3″ larger in diameter) or more. Please call one of our stair designers, we can often work out a 5′-0″ diameter in tighter spaces, depending upon wall locations below.