anchoring wood railing posts on concrete
suzycarpenter
| Posted in Construction Techniques on
My client wants a pressure-treated railing with 4 x 4 posts installed on existing poured concrete steps — a short run, just four steps and a landing. Is there any boot/foot/base that will provide enough stability for the post once it’s anchored? Thanks!
Sue
Replies
Half-dozen different options, none of them good.
Dan is right; if there's nothing but a straight run of rail, the 'boots' won't hold up for long to even a ten-year-old's pushing sideways on the railing. At a minimum, you will need to tie the top of the railing to the house and put an angle brace at 90 degrees to the run of the rail at the newel post. Not easy or elegant to do with 4x4.
Second comment: using PT lumber for skin-contact items like a handrail is a bad idea. This stuff is not finish lumber and splinters are virtually inevitable over time. You don't want to get splinters of PT into your hands.
Has your client considered wrought iron?
Dinosaur
How now, Mighty Sauron, that thou art not brought
low by this? For thine evil pales before that which
foolish men call Justice....
Simpson ABU-44
The Simpson comes with the following caveat: "Post bases do not provide adequate resistance to prevent members from rotating about the base and therefore are not recommended for non top-supported installations (such as fences or unbraced carports)."Not to mention the fact that it doesn't look good. Sigh. Sue
Suzy
There was a discussion here about a year ago dealing with how to fasten a post to a concrete floor and some really good ideas came up. You can hope they will again. Finding that discussion through the search here is unlikely.
I can vaguely remember what I suggested at the time, but there were things I thought were better than my plan. I suggested embedding threaded rod in epoxy in a hole drilled in the concrete and building a post around the rod with 2 pieces of 2 x 4 and two 1/2" fillers.
With stairs, it would be easier and stronger to fasten the posts outboard, say to the second step. in order to get some lateral stability. You might be able to do that with lags and lead shields if the concrete is in good shape.
Ron
Probly dumb question, but is there anything in the way of placing the posts along side the steps instead of on the steps?
The top post can be anchored to the concrete steps if along side.
The bottom post can go in the ground along side the bottom step and also anchored to the bottom step for additional lateral support.
Work for you in this application?
"Let's get crack-a-lackin" --- Adam Carolla
It's the best idea I've heard yet, although it doesn't fit the drawing they gave me of what they want (which showed the posts coming down to meet the top of the steps). I may need to go back and discuss this further. Thanks.... keep the ideas coming.
Sue
If it's technically possible to mount the posts on the sides of the steps, but they don't like that appearance, then a piece of, say, 1" square steel tubing about 3 feet long can be attached to the side of the steps and to the posts, allowing the posts to still rest on the tread.The steel can be painted to have a wrought iron look, so not too obnoxious looking in most cases.Another relatively standard solution is to imbed steel posts into the concrete, then place the hollow wood posts over them. Requires drilling a good-sized hole in the concrete to imbed the steel and also figuring out how to drill the wood posts. You need at least a foot, preferably about 18", of steel post in the wood to assure stability, and drilling a hole that long (and straight!) is tricky.If the concrete isn't poured yet, and it will be sufficiently high above grade, one could form a post pocket in the concrete, with a formed-in drain to daylight at the bottom, and some sort of provision to through-bolt from the side. The pockets would need to be 8-12 inches deep.
If Tyranny and Oppression come to this land, it will be in the guise of fighting a foreign enemy. --James Madison
Hi Sue,
I've posted this before, but the search function takes getting used to, so here's the short version.
Drill 4 holes 6" deep by 5/8" diameter in the bottom of each 4x4 post. Center the holes about 1" from the corners, and drill slightly toward the center of the post, i.e. the holes are slightly angled in. Use Simpson epoxy to glue 4 pieces of 1/2" all-thread or 3/8" rebar into those holes.
When the epoxy cures, the protruding rods can be bent so they exit the post parallel to one another and to the post's long axis. Now drill 4 holes in the concrete for each post, same size and depth, all straight down. Brush and blow out all the dust.
Mask off the concrete around where the base of the post will rest. Mask off the sides of the post at the bottom. When that is done, put a fresh nozzle on your Simpson gun and put epoxy into the slab holes, and set the posts. Quickly brace them plumb. While the epoxy is soft, smear the excess away from the bases with a gloved finger, and carefully remove the masking while things are still squishy.
Take lunch, or work on something else. The posts will cure solid in an hour or several, depending on temperature, etc. When they are cured, they will feel like they grew there.
I hope this was clear. I've done this many times, and it never fails to impress the customers.
Bill
Ah.... it sounds like we're on to something now that these clients will be happy with. Thanks.... keep any more suggestions coming. Sue
Sue,On high dollar projects I use 1/2" stainless steel all-thread. It is stronger and also more corrosion resistant than mild steel. It is also overkill for many applications, since the epoxy encapsulates the steel pretty well when done conscientiously. Also, when gluing the rods to the posts, use the epoxy to seal the bottom of the post, to forestall major wicking of moisture in service.Another thing is to try and avoid drilling through the bottom of the concrete, as this could let the epoxy run out, starving the joint. If one hole runs through, shorten the other 3 and trim the corresponding rods. Even 4" of engagement in the slab is very stout.I once had to demo a post I'd set this way, after a few years. The way I got it off the concrete was to cut the redwood just above the steel dowels, then splinter the remaining wood with a sledge. Once the wood was gone, I was able to cut the dowels flush with a Sawzall.Obviously, careful layout is a must with this method. Your customers will be pleased. Cured posts ring like a tuning fork when struck sideways at the top.Ditto what another poster said about not using treated wood for a grab rail.Bill
I don't have the Simpson epoxy, and it looks like Home Depot is the only place that carries it (HD is an hour away). I'm guessing it's important to use the Simpson? I do have West System epoxy and other adhesives, but, from their website, the Simpson sounds pretty specific for this application.....? Sue
Sue,I have done this with WEST System also. The Simpson sets faster and is really easy to inject into the holes as a thickened mass. It is good to add some graphite to the WEST so that the edge fillets don't break down from UV exposure. Thicken with colloidal silica or high density to get the strength you need. In WEST parlance, what this constitutes is equivalent to their "hardware bonding." Low density fillers could cause the connection to fail prematurely.If it is sunny/warm when you do the post dowels (i.e. the steel to wood gluing) the graphite accelerates the cure if you let it get hot in the sunlight. Don't overdo, or you'll get bubbles. With WEST epoxy, your mix needs to be less thick so you can pour it into the holes and not have voids. I first did it this way, and found the Simpson to be easier. On Breaktime, I figured more readers would be familiar with the injectable epoxies. Simpson isn't the only brand of this product, but has very wide distribution in HD and lumberyards.So go for it!Bill