curved stringers
I built a curved stair a few years ago. As far as I can remember the outside radius was about 10', with the inside radius, a wall built by the framing crew. I established the outside radius on the floor, about 4' from the inside. Built a temporary wall at that line, with every other stud at the face of the riser. Useing a story pole, I then established each tread on those studs. then laminated 1/2" plywood, screwing the first layer to the studs on that line, then 3 more layers glued and screwed to that one. After all layers were glued up inside and out, I layed out the treads and risers. then before cutting it all out I installed my rough risers in between the two stringers, glueing and screwing it all together. At this point the false wall can be removed, and everything cut out. I then added 2 by material as rough treads between the stingers to strengthen it more. The finished product was very strong and graceful.