you need to re read your code
(3) Profile: The radius of curvature at the leading edge of the tread shall be no greater than nine-sixteenths inch ( 14.3 mm). A nosing not less than three-fourths inch (19 mm) but not more than one and one-fourths inch (32 mm) shall be provided on stairways with solid risers. The greatest nosing projection shall not exceed the smallest nosing projection by more than three-eighths inch ( 9.5 mm) between two stories, including the nosing at the level of floors and landings. Beveling of nosing shall not exceed one-half inch ( 12.7 mm). Risers shall be vertical or sloped from the underside of the leading edge of the tread above at an angle not more than 30 ( 0.51 rad) degrees from the vertical. Open risers are permitted, provided that the opening between treads does not permit the passage of a four inch diameter (102 mm) sphere unless one of the following applies:
(a) A nosing is not required where the tread depth is a minimum of eleven inches (279 mm).
(b) The opening between adjacent treads is not limited on stairs with a total rise of thirty inches (762 mm) or less.
open risers are only allowed if the total rise is 30" or less.