Stabilizing Half Wall

I'm doing some reno and took out a free standing closet but left the remaining wall as a half wall

The problem is the left side of the wall (by the empty electrical box in the pic) is wobbly. From what I read, the best way of stabilizing it is to drill into the subfloor and secure the stud into the joist. However, the basement is finished and there isn't a joist directly below the wall so adding blocking would be very difficult.

Another idea was to double up the outside 2x4 but I want to keep the wall as small as possible so I don't want to do it on the outside. I don't think doubling on the inside is possible due to conduit coming out of the bottom and not having enough room to line it up with the junction box.

I can't put a layer of plywood up since there are stairs in the way. (maybe possible on the other side?)

What are my other options? So far, I thought of adding L brackets to where the studs meet the bottom plate, blocking between the studs and adding a second top header.

 

First, replace the stud that is cut off for the thermostat. A stud that doesn't go all the way up to the top plate is almost useless. You might have to relocate the thermostat to the left so there is room for the box and doesn't require completely cutting a stud in half.

Next adding a top plate will help by tying the tops of the studs in the tiny half wall together. A steel angle bracket across the top tying both walls together will help immensely and the longer the legs on the steel bracket the better.

Screw down the bottom plate to better anchor it to the subfloor. Then you can further reinforce the short wall by installing steel angle and/or corner brackets at the bottom to firm up the studs connection to the bottom plate.

 

What about doubling up on that cut off stud? I might be able to fit the second one to the left of it and that way, I won't have to move the thermostat.

I'll definitely take a look at the adding more screws and plates to the bottom!

 

Yea, a second full height one right next to the cut one will be fine.

Steel is your friend. Most home centers have a section, usually near lumber, with a variety of metal brackets. Installed with screws they can really firm up the joints in your wall and are cheap and easy.

 

I don't see why you can't add plywood to the outside. That would stiffen the wall greatly.
All you need to do is notch the plywood around the two stair treads, you will have to notch the drywall anyway in the same manner.

I would use 3/8" Structural one grade ply and 1/4" drywall. Nail or screw the plywood all around the perimeter at 6" oc.
Brackets will help but I'm not sure it would be rock steady.

 

I wanted to keep the wall at 5/8 and didn't want to make it extra thick. I didn't realize they made 1/4" drywall. I'll look into this too. Thanks!

 

This may be a bit unconventional, but it would work well.

Since they dont really make corner bracing big enough... Buy a 24" framing square. One side is 24" long, the other is 16" long. Drill a few holes in each side of the framing square. Once you put your top plate on, screw the framing square to the top of the wall. It will be super sturdy.

 

Does OSB work too instead of plywood?

 

I would not use OSB, it is too thick as far as I know. I would use 3/8" ply, it can be struc I (no voids) or regular plywood.
Be aware that 5/8" drywall only will stiffen the wall also. If you go with 5/8" drywall, screw it every 6" and don't sink the screws too deep, just a shallow dimple.
You are just trying to create some kind of diagonal brace and plywood or 5/8" drywall qualifies.