My stairs have walls instead of a balustrade. The walls are not load bearing and are only about 4 feet high in place of railings. I would like to remove these walls and replace them with a balustrade.

I got a book on stair construction so I think I can handle the treads and baustrades.

What I'm not totally clear is what I will have to do after removing the walls down to tread level. I'm guessing there will be the ends of framing 2x4's showing. I don't think that these framing members directly support the stair stringers but nevertheless I suppose that bracing will have to be added to stabilize the vertical framing members. I need to remove a tread to see what it looks like inside but I was hoping someone could tell me if my thinking is correct and if something like this is even feasible.

Thanks