Final answer:
The maximum radius for a stair nosing curve should be 1/2 inch, and nosings are not required if the tread depth is 11 inches or more, which aligns with modern stair design codes.
Step-by-step explanation:
The radius of a nosing curve should be no greater than 1/2 inch. A nosing is not required when the tread depth is 11 inches or more. In stair design, nosings are the part of the tread that protrude beyond the riser beneath; codes and recommendations can change over time. Traditionally, older recommendations suggested the dimension ratios of 5 side-to-side and 7-8 deep, but more recent analyses recommend even larger dimensions such as 8 diameters side-to-side and 15 diameters deep for different components.