I built my own stair case from scratch. When buying a kit be very careful about all the steps being of equal height AND fill your floor to floor distance EXACTLY. My Brother in Law, got a builder to put a flight of stairs in his barn. The chap bought a kit and fixed them up. Because of the above problem each step has a noticeable slope on it. I would say that the distance has to be within 1" on a 14 step flight.
As a side note, the builder had already put in the new upper floor. Err, perhaps he should have measure up or bought the stair kit before he did this!!
Frank