You may recall, we left off here:
Then Justin did this:
It's just standard framing, and wasn't super sturdy at this point despite being well attached to the floor. So, Justin did this:
And what a difference it made! It's just a 1/2" thick sheet of plywood that's attached to the framing with construction adhesive and screws. It prevents the wall from bending at all which decreases the wobble. He screwed the drywall back onto the other side and called it good-for-now.
The next step will of course be drywall, trim, and paint. It was really important for us to get this wall as sturdy as possible because the handrail for the stairs attaches to it on the other side. Even though it's far from finished, it feels a heck of a lot better! I think the plywood may even be an improvement over the blue walls and trim we started with...