By default, most stairs (except porch stairs) have an overall height of 9’ and have 18 steps. You can edit the general dimensions of a staircase, such as height, width, and number of steps. You may want to familiarize yourself with the parts of a staircase before editing these properties.
To edit stair size properties:
Select the staircase whose stair properties you want to edit.
Right-click and select Properties, or select Edit > Modify Elements > Properties.
In the Stairs/Ramps dialog, edit the dimensions in the Properties window.
Click OK.