Spiral staircases generally range in size from 42" to 76" in diameter. The floor opening at the top of the staircase must be two-square-inches bigger than the staircase's diameter. Spiral staircases are also measured by their floor to floor height, footprint, walking space, and landing length.
How do you frame an opening for a spiral staircase?
https://www.youtube.com/watch?v=lMth3Glvm10
What is the standard size of a spiral staircase?
Spiral staircases generally range in size from 42" to 76" in diameter. The floor opening at the top of the staircase must be two-square-inches bigger than the staircase's diameter.