Spiral staircase

These are a type of stairs that can be both self-supporting and made of concrete. They are characterized by overlapping steps with non-parallel shapes. There are several types of winding stairs:

• L-shaped single-flight stairs
• 2 x 1/4 turn stairs
• 1/4 turn stairs with landing
• 1/2 turn stairs
• Arc-shaped U-shaped stairs
• Circular stairs.