A rectangular spiral staircase?

68gtxman said
If doing more than a 50% renovation, then everything must be brought up to current codes. The IBC says that the minimum tread depth on winder treads is 6”.

So the treads that taper down to nothing are not code compliant today. Just sayin’ for a friend.

I don't think that applies, exactly. A quick search shows up...................Of course some local codes might be more strict.........

Spiral Stair Building Code Compliance

Minimum stair diameter of 60" for a metal stair and 64" for a wood stair
Tread path between handrail and center column a minimum 26"
Center tread width, 7 1/2" in from the narrow end of the tread d
Headroom minimum of 6'6"
Riser height cannot exceed 9 1/2"
Baluster spacing of no more than 4" (to prevent children from sticking their heads between balusters)
Minimum height of the handrail of 34" from the tread nosing to the top of the handrail
Landing width, 4" longer than the tread path
Rail height on the landing, well and balcony rail has a minimum height of 36"
Weight capacity, a minimum of 300 pounds per square foot