Background
At the front of my house I have concrete steps leading up to the porch. Having just rebuilt the porch, I've discovered that they are actually concrete veneer over brick. It appears that the concrete is roughly 2-3" thick.
What I want
I'd like to add a hand rail to the steps since there's never been one there. We want to use 4×4 posts and will install an angled wooden railing between the posts to match the railing we'll be installing around the porch.
What I tried
To anchor the 4×4 pressure treated posts to the steps, I attempted to use this 4×4 U-bracket:
All images from Lowes.com unless otherwise noted.
I bolted it to the steps with a 1/4" x 3-3/4" Tapcon screw through each of the 4 smaller holes in the bottom:
As I was drilling the holes, I got a bit of red debris coming out of the holes, so I believe I hit brick under all of them.
Screwing the Tapcons in, a couple of them refused to go all the way in with my impact driver. Thinking "all I need is a bigger hammer!" I put the 5/16" socket on my 1/4" drive ratchet handle and gave it a couple of gentle tugs until the bolt turned. Unfortunately, I put more torque on it with a short ratchet than the bolts were designed for and sheared 2 of them in their holes. I replaced the sheared bolts with shorter (2 1/2") Tapcons. I got all 4 Tapcons fully seated against the metal bracket, dropped the post in place, squared it up and nailed it in with 8 joist hanger nails. Unfortunately, the post wobbles.
It appears that this isn't the ideal method for securing a wooden post to existing concrete over brick steps.
What I don't want to do
Obviously, I have no desire to break up the perfectly functional concrete steps to repour them with a couple of cast-in-place bases, even though that would probably be the ideal solution.
What I'm thinking is the next step
Would I be able to use this cast in place base:
By drilling a large hole for the center bolt and using an expanding fastener like this:
Note: I don't think I'd need a 6" length, that's just the largest diameter one I could find a picture of. I don't know the diameter of the center hole of the bracket, but I would find a suitable size anchor and an extra washer for under the bolt if necessary.
A possible alternate method
Would it be possible/reasonable to attach the posts to the side of the steps by drilling through the 4×4 posts and running long bolts through them and into the side of the step? What kind of anchor could I use that would be long enough to do that? Does anyone make a bracket that would wrap around the post so that I can attach the bracket to the concrete with "normal" length fasteners then attach the bracket to the post with wood screws/lag bolts/joist hanger nails (thinking a bracket like this)?
Bracket in red with concrete anchors in blue and lags in orange. Source: Me! Copyright: Seriously? You want to use my MS Paint drawing? Sure, what the heck. Go for it.
The ultimate question
What should I do to attach my 4×4 posts to my existing concrete steps?
Best Answer
I think you just about answered your own question.
I would attach the posts directly to the sides of the steps, with the posts extending down as far as possible. This will get you more bearing surface between the posts and the steps, and allow for more anchors in the masonry spaced further apart. This will make all the difference. I think the sheet metal mounts will always be prone to wobble.
The expanding sleeve anchors in your question are probably as good as anything for this, make sure you use long ones, even with 2x4's. In perfect concrete with a perfect hole, you wouldn't need that much embedment to secure the wood adequately, but this masonry is questionable compression strength and quality, so I'd go for as much embedment as possible. The 5/8" x 6" pictured in your question is probably just right, you'll have over 4" of embedment and that should be very strong.
I might use 2x4 rather than 4x4 posts. The thicker the wood, the less embedment of the anchor, and the more it will wobble; this may be hard to picture, but with a 4x4, the lever arm you have between the head of the fastener and the anchoring in the concrete is doubled. You're not holding up a deck, just a hand rail, 2x4s are adequate. You could also shorten the lever by countersinking the nut and washer into the 4x4.
Another way to go would be to double up two 2x4's, with the second 2x4 inside the first, with its butt sitting on the top of the step. You could get the same effect by rip cutting a half-lap into a 4x4. This might be the sturdiest of all, since the butt bearing on the top of the step would stiffen things a little more.
By the way, for future reference - when tapcons break like that, it's usually because there's some dust left in the hole from drilling, you can blow it out with canned air or other method.