Ground posts–or posts that are seated in concrete below ground level–are notorious for working themselves loose over time. Whether a ground post is holding up a mailbox, a section of fence, or a porch handrail, leverage will eventually cause it to sag or wobble.
This article will show you one great trick for making your ground posts as strong as possible! I’ve included a short video tutorial as well.
(The ground post I’m strengthening in this project happens to be holding up the lower end of a handrail, but it’s important to note that this trick will work for any situation where you’re seating posts below grade in concrete bases.)
Drill (or) Driver
4×4 Treated Post
3″ Exterior Screws
50 lb. Bag Concrete
(Tools and materials are linked below strictly for informational purposes–no marketing revenue is generated through these links.)
1. Why Posts Wobble
It’s rare that I grab a handrail leading down a flight of exterior steps and don’t feel it shake in my hand. This is because posts situated in the ground typically have far less support than posts attached to structural portions of a deck, porch or house.
These ground posts are at least partially anchored in concrete bases. As the posts shrink, or experience too much leverage from people leaning on the handrail, they tend to loosen the bond of the concrete surrounding them. This effect only worsens as both concrete and post continue to erode over time.
The technique I’m going to show is a really great trick for preventing this problem. And it only requires a handful of exterior screws!
2. Mark Ground Level On Post
I’m pre-supposing here that the hole for your post has already been dug, and the post has been cut to length. (As a general rule, you want up to 1/3 of the post height situated below ground level. I tend to make mine at least 20″ deep.)
Just drop the post into the hole and make sure it’s standing vertically. Use a pencil to draw a line on all four faces of the post at ground level. Then, lift the post back out and find a good place to lay it down, preferably on a work table.
3. Partially Drill Screws Into Post
With the post lying horizontally, begin embedding 3″ exterior screws into the wall of the post below your ground level mark using a drill or impact driver. You only want to sink the screws about halfway, and ideally you want to drive them at a bit of an angle.
Use two or three screws for each side of the post. If your post has to sit up against brick stairs, or wooden stair stringers, be sure to avoid embedding screws on that side of the post. They will prevent it from sitting flush to the structure.
For any free-standing posts out in the yard, and especially for fence posts, you can feel free to embed screws into all faces of the post.
I call this process creating a “screw tree.” These exposed screw heads will provide anchoring points for the post when concrete is poured around it.
4. Set And Plumb Post
With your screw tree in place, you can go ahead and set the post back into the post hole. Make sure nothing is obstructing it from sitting where it needs to sit. Roots, rocks, and bits of masonry should be dug out or broken off to provide plenty of clearance.
Position the post upright, and check it for plumb. I like to use a post level to do this. The L-shaped tool has three spirit gauges. You just rubber band it to the post, and check the two bubbles that indicate plumb.
When you have the post where you want it, make sure it doesn’t move. You can tack a couple pieces of scrap lumber to with trim nails just hold it in place. (Later, they can easily be removed with a claw hammer.)
5. Pour Concrete
A lot of fence builders don’t even wet their concrete powder. They just pour it dry and then let ground water slowly seep into it over the next day or two. I like to speed up the process by pouring some water directly into the hole first, then dump them mixture down into it.
You can use a long pry bar to mix the two parts down in the hole. (This also helps force concrete down into little voids, making sure it is well compacted.) Do about half the needed amount at first, then add a little more until you’ve covered all the exposed screws.
Leave the surface of the concrete just below ground level so you can hide it with bark, mulch or grass. (Nobody likes unsightly blobs of concrete right at the entrance to their home.) But, use a margin trowel to slope the top edge of the concrete boot into a sort of cone. This will help shed water away from the post, preventing rot over time.
Just repeat this process for any posts anchored into the ground, then let the concrete mixtures set up for at least a day. When they’re ready, remove any temporary supports and test the railing for sturdiness.
I’ve always been amazed at how much stronger posts are with screw trees in place! And, as the post slowly dries out and shrinks, the screws will continue to ensure that the railing doesn’t lose its rigidity.
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