You may choose to enhance the look of your single open staircase by adding a single volute stair tread to your stairway. If this is the case you will need to know how the fitting sizes are sold for a LH -or- RH Starting Tread:
Understanding The Sizing Of Single Volute Stair Treads:
The true overall size of a 48 inch ( in. ) single volute tread is: the 48 in. back inside square edge, plus the 10-3/8 in. overhang. So, a 48 in. single volute tread ( if the inside fitting size is equal to 48 in., has a total length of 58-3/8 in. ). Note a 45 in. inside fitting size would simply yield a total single volute tread size of 55-3/8 in. ( 58-3/8 in. - 3 in. ).
When talking fitting size it is very important to understand that the inside back square edge is all the that matters. So, with a single RH volute tread this size would be would be the 'inside side left side skirt -to- out side right side skirt measurement' or the 'inside side left side drywall -to- out side right side drywall measurement' ( if you have no skirts in place ).