These are two model codes and are offered as suggested guidelines for local code authorities to follow at their discretion.
Building basement stairs code.
The nosing on treads believe it or not has a code minimum and maximum of how far the nosing projects over the next stair.
Imagine having a 12 high stair in place with a riser height of 9 and a tread depth of 9.
This stair would have 16 treads 9 deep for a total run of 11 3.
Minimum 6 8 headroom height clearance for stairway.
To a maximum of 1 in.
Maximum 12 3 vertical height rise for a flight of stairs.
The international residential code for one and two family dwellings irc and the international building code ibc address staircase railings.
A prime example is the standard stair width.
Staircase code states that stairs must be 3 feet wide or wider.
There may be local or state building codes for how many inches off center you can space studs such as 16 or 24 inches apart and how much clearance you need for ceilings landings for the bottom of stairs and the height and depth of the steps.
As long as the 3 foot width standard is met you can expand the stairs width as far as you wish.
Maximum 7 3 4 inch stair riser height.
Building codes often require insulation and moisture barriers.
Minimum 10 inch stair tread depth with nosing or minimum 11 inches with no nosing.
Irc stair railing code.
At the same time staircase code measurements do allow for some flexibility since most measurements are accompanied by minimums or maximums.