Framing stair knee wall...
 

We are converting a 3rd floor to finished space. I am framing in a knee wall for the stairs and have a question on how exactly I should frame the portion of the wall that actually comes down the stairs. The stairs were framed with the open stringer but we decided against an open stairs case and go with a knee wall.

First picture...
I would remove the outside most stringer and replace with (2) 2x12" then build the wall on top of that.

The second picture...
I remove the stringer and build off the slope of the stairs. This way I could block in the studs against the other stringer to give more rigidity on lateral movements.

The third picture.
I remove the outer stringer and re-frame the wall to extend it horizontally then build a "rake wall" that is the stairs. This might be the most structurally sound but also the hardest to do.

Please, thanks for your help!!

Or, #4 would be to rebuild the the wall like #3 but further down. This, IMO, probably will work the best since it will have hardly no lateral movements and it would be easier to frame.

I think, when finished, #3 or #4 would look the best. But why would you build this as a rake on top of a wall? Why not build it all as one tall wall with a raked top?

That's what #4 aims to do without having to rebuild the entire wall from the floor up. I *could* just rebuild the entire wall and rake the tops of the studs but that would take some extra work on my part (having to maneuver around the stars to nail the studs into the bottom plate). If it's only a matter of aesthetics then I will probably do #4.

Also, with the pseudo-raked wall i probably need to have fireblocking since the stairs traverses 2 floors, right?

Also, is a single top plate for this wall adequate? With the let-in brace it is really sturdy, but not sure if the inspector will demand it or not.

Not sure how much the open stairwell wall will require fireblocking, and if so, exactly where.

Termite did an EXCELLENT series of articles on fire blocking in the "How To" section you might check out. I don't think there's much he missed.

I would double plate only for the reason of the possibility of just a single plate developing a warp over time. Two oppositely crowned 2xs eliminate that.

Number 3 and 4 encroach into the lower stairwell, narrowing it by 3-1/2". (Minimum 36"net/finished) It appears your top riser is 1-1/2" shorter than the others, did you remove the tread thickness from the bottom riser before cutting? Your risers appear to be more than 7-3/4", may want to verify that with your local building department. It's just so easy to trip on stairs, is why I mentioned it. Or... I may need to clean my glasses....
Be safe, Gary

I actually just removed the outer most stringer and simply extended that wall up. The stringer was sitting on a 2x4 top plate. The stairwell is 39" wide.

The treads you see are 2x8" that the builder put in for temp steps. I have a 8"/10" rise/run so the I got stock 2x12 with 3/4 ply risers to be put in this week. This will give me a nice 1 1/4" nosing to wrap the carpet around and 1 1/2" of spce on each side for drywall and skirting.

Will post pictures tomorrow... battery in camera is dead :)