S.C. Code Regs. 8-1210. IRC Section R311.7.5.1 Risers

The maximum riser height shall be 73/4 inches (196 mm). The maximum riser height for masonry stairs shall be 8 inches (203 mm). The riser height shall be measured vertically between leading edges of the adjacent treads. The greatest riser height within any flight of stairs shall not exceed the smallest by more than 3/8 inch (9.5 mm). Risers shall be vertical or sloped from the underside of the nosing of the tread above at an angle not more than 30 degrees (0.51 rad) from the vertical. Open risers are permitted provided that the opening between treads does not permit the passage of a 4-inch-diameter (102 mm) sphere. Exceptions: 1. The opening between adjacent treads is not limited on stairs with a total rise of 30 inches (762 mm) or less. 2. The riser height of spiral stairways shall be in accordance with Section R311.7.10.1.