And convenience

Given these features of the spiral staircase, the assembly can be performed both in the factory and directly on the spot.

The height of the aisle is the minimum distance in the vertical plane between the lower edge of the existing constructive element and the upper edge of the step located under it. Typically, the openings above the stairs are constructed simultaneously with the stairs and their dimensions should provide freedom and convenience for the passage of a person. As a rule, they are 1.9-2.0 meters.