Help building a half wall.


Hi all, I want to get some validation on a plan I have, and some help on the execution. Basically I want to build a half wall that anchors to an outside wall on one end, and is free standing on the other end. The wall needs to be 12' long. Here is a simple picture of my situation:
http://ryanandali.com/images/halfwall.JPG
<a href="
http://ryanandali.com/images/halfwall.JPG ">half wall diagram</a>
The half wall I highlighted in red is currently a cheap metal rail. I want to replace it with a real wall. The floor joists run perpendicular to the wall I want to build, and I don't have any problems cutting through the floor to them - I'm replacing the flooring anyways.
Basically what I want to know is: 1) should I be using 2x4 or 2x6 for the wall? 2) will it be stable enough to prevent someone from leaning against it, toppling it over and falling into the staircase? 3) will I need to anchor it to the floor joists with something more robust than deck screws?
And lastly, where can I find a wooden "cap" for my half wall. I'd like something that matches the wood floors I'm going to lay down.
Many thanks for any insight into this little project =)
-Ryan
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snipped-for-privacy@gmail.com wrote:

2x4s are heavy enough if you sheath the frame with 3/8" lauan. That creates a torsion box, which, if turned sideways and anchored through one edge, will be stiff enough to support a man's weight. The sheathing adds most of the stiffness by its resistance to compression and tension. The framework serves only to hold the sheathing panels apart. Actual frame material is less important than its width (2 x 4s are plenty wide).

Deck screws don't take shear forces well. Use 1/2 lags. Anchor it also the adjoining wall. You might need to sister or block a few studs to provide secure attachment.

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It should be ok with 2x4s, if they're solidly anchored to the floor. It will be at least as good as whatever open railing you replace. (*)The FLOOR, not whatever covering you put ON the floor. welding gluing it to the plank flooring just means that the plank comes loose from the subfloor. (**)Ok meaning that under normal loads it won't collapse. If someone decides to climb on it, or slams into it while running, or tries to balance a 50" TV on it, you may end up needing repairs.
Any of the following will make it more stable:
1: running one or more posts straight through the floor into the wall below. 2: Running a post to the ceiling at the free end. 3: Having a 90 degree "return" for a few inches at the free end. ('L' shaped wall, in plan view.) 4: Making it wider. 5: oddly shaped metal brackets attached to the wall above and below the upper floor. 6: Big-ass steel 'L' brackets embedded in the wall and under the flooring.
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a 2x4 or on the end of your half wall through the floor plywood to a piece of blocking fastened to the floor joists. don't see that you gain a thing with sheathing. that would prevent racking in the plane of the 1/2 wall, but since one end of your half wall is tied to another wall, racking isn't a problem.
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If you are willing to cut into the subfloor to get to the floor joists, I'd do that and take the studs in your 1/2 wall down down along the side of the joists (or a few or them anyway) and bolt them thru the joist.
Assuming you are using prefinished flooring, the manufacture may have something you could use to match, or you could simply put flooring on as the cap.

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Excellent info! Thank you all for the replies! I've decided on 2x6, more for asthetic reasons than structural. I'm going to run the end stud down into the floor and double bolt it to the joist to stabalize the "weak" end. Thanks again!
-Ryan
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You may also want to do the same at the wall's midpoint. You'll notice a difference.
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