Stairs made in shops and then brought to the job are
considered prefabricated stairs. Prefabricated stairs range in all
shapes and sizes from regular Straight run stairs to complicated
The biggest problem with buying a prefabricated stair stringer from your local hardware store, is that these stair stringer's might not fit correctly. If this is the case you'll have to modify, either the stair stringer or the floor system it is going to attach to.
It's not always going to be in your best interest to buy something like this, because it could create a trip hazard if the risers are not equal lengths.
Stairs built in the shop requires the lumber to be brought to the shop and then the stairway assembled and then brought out to the home site. The stairs built in the shop where you normally have all of your jigs and tools could have its benefits were as someone Building the stairs on site might forget the tool which will slow down the process requiring them to go get the tool which could be labor intensive.
Prefabricated curved stairs usually takes a while to build due to the difficulty involved, it seems to take a lot of time figuring the geometrical shapes and tangents for these stairs. Most track framing stairs will be built on site using skilled carpenters.
There as been arguments going on for years, whether it is more cost effective to build a set of stairs in a shop and bring the stairs to the job or is it better to bring the materials to the job site and build the stairs. This debate has been going on for years and it seems like the on site stair framing is winning.