The tread is the part of the stair that you step on. In UK building parlance, it is called the "going." It is an important safety measure to make sure you have an appropriate amount of tread surface. The riser is the vertical space between the tread. The nose or nosing is the trim on the outside edge of the stair tread. It usually has a bull-nosed profile.
The UK building regulations states that stair treads must have a minimum depth of 220 mm (8.66 inches) for a private house. Institutional buildings and places of assembly must have a going of at least 280 mm (11 inches) on their stairs. All other buildings must have stair treads that are at least 250 mm (9.8 inches) deep.
The UK building recommendations (called "Document "K") does not impose a minimum width of stair tread. However, building industry recommendations suggest a minimum stair width of 600 mm (23.6 inches), with a recommended width of 850 mm (33.5 inches).
The steps on a winding, or circular staircase must all be equal around the centre depth of each tread. The depth of each tread should conform to the minimum requirements for the stiarcases location (private/institutional/other).
The surface of the tread must be slip-resistant and be well-maintained and of satisfactory quality.