504.2 Treads and Risers.
All steps on a flight of stairs shall have uniform riser heights and uniform tread depths. Risers shall be 100 mm (4″) high minimum and 180 mm (7″) high maximum. Treads shall be 280 mm (11″) deep minimum.
504.3 Open Risers.
Open risers are not permitted.
504.4 Tread Surface.
Stair treads shall comply with 302. Changes in level are not permitted.
504.7 Wet Conditions.
Stair treads and landings subject to wet conditions shall be designed to prevent the accumulation of water.