Spiral staircase with open risers

[Ken Amelin]

I inspected this home and have questions regarding this beautiful staircase.

I am familiar with tread width requirements and spacing between balusters, but what are the current codes regarding open risers and nosing overhanging the treads?

Thanks

[Fred Weck]

Riser opening less than 4". If the risers are solid the nosing shall be between 3/4" - 1-1/4".