Concrete fence posts aren’t like their wooden counterparts. Drilling through them or into them increases the likelihood that it will split or that it will crack down the middle. Either way, you’re left with a fence post that’s no longer as structurally sound as it once was.
That doesn’t mean that you can’t drill into a concrete fence post, however, it just means that there is a methodology to it, certain tools, and a bit of caution are required.
Concrete is a cheap, durable alternative to using wood posts, which are far more vulnerable to weather and strain than concrete posts are. But concrete comes with its own set of problems. If some of your fencing comes down or you need to repair it, drilling is sometimes your only option.
The Problems With Drilling Into Concrete
From a structural standpoint, concrete isn’t just the mortar. Even a standard concrete post is full of aggregate—small or large rocks—which aid the surrounding mix in terms of stability. Unless you’re dealing with grout, concrete is most likely going to have aggregate.
There is also the matter of rebar. When it comes to concrete posts, there are usually three or four, vertical sections of rebar running up the length of the concrete post. Since these are posts and not concrete slabs, the rebar is usually not too thick.
If you don’t use the appropriate drill and drill bit, you’ll either strip the drill bit and make it useless, or you’ll do damage to the concrete, possibly to the point where it is no longer a viable fence post.
How To Drill A Concrete Fence Post
You’ll need two things in order to drill into a concrete fence post—three if you want to count patience. You’ll need what is called an SDS (Slotted Drive System) drill and a particular type of drill bit, specifically a masonry drill bit with a tungsten-carbide tip.
The drill bit you go with has to be able to fit an SDS drill.
The most important tip you need to know before you start drilling is to be patient and go slow and steady. Make sure that you keep the drill in a straight line, horizontal to the fence post.
When you get started, go with the smallest drill bit that you have first, even if it’s much smaller than the hole you want to drill.
- Start drilling in, slowly and steadily
- If you hit rebar, start over from a new location
- Routinely withdraw the drill bit and blow out excess concrete dust
- Once you’ve reached your depth, replace it with a larger drill bit
- Increase the size of your drill bit until you reach the right sized hole
You also need to make sure that you wear the proper protective equipment. Just because you know what you’re doing doesn’t make your ears, eyes, and lungs special and otherwise resilient to things other human beings are vulnerable to.
An SDS drill runs at high enough decibels to severely damage your hearing at sustained levels. Concrete dust can do permanent damage to the eyes, especially if a fleck of it strikes your eye at a high velocity.
Concrete dust is also known for causing long-term respiratory problems. The cough that you experience now may transform into something altogether worse later on down the road of your life.
What Are The Risks Of Drilling Into A Concrete Fence Post?
So long as you’re wearing the appropriate PPE (Personal Protective Equipment), the risks to you are pretty minimal, aside from potentially getting covered in concrete dust. As far as drilling into the post, however, doing irreparable damage is a prominent risk.
Stick to the exact, center of the post to avoid any rebar. While this might not always avoid rebar, it’s not likely that the concrete was poured in with a rod of rebar situated directly in the center of the mold. Rebar is the most prevalent issue that you’ll run into.
If you’re drilling all the way through, you risk a chunk of concrete blowing out of the back when your drill tip penetrates through the last of the concrete. To avoid this, routinely withdraw the drill bit and blow out the concrete dust.
Blowing out the concrete dust periodically helps reduce the pressure on the concrete that your drill bit is busy drilling through.
Cracking is another problem. The only thing that you can do is start with a small drill bit and increase the size a little bit at a time. This way you’re widening the hole a bit at a time without going full-bore right at the beginning.
You can also avoid cracking by going straight in, as level as humanly possible. If you can, purchase an SDS drill that also has a bubble level in it, that way you can watch and make sure that you’re going in as level as possible.
Lastly, avoid slipping—if at all possible—and applying pressure to the walls of the hole you are drilling as you are drilling it. Pulling downward or pushing upward is a good way to compromise the concrete and cause it to crack.
Would It Be Better To Replace The Fence Post?
Only if you simply can’t drill through it without causing a large amount of damage. It’s not costly to pour a concrete mold for another fence, but it is more labor-intensive and time-consuming.
It is very difficult to drill through a concrete fence post. It’s not something that can’t be done, but it is hard to do without causing cracking or other structural damage. If you simply cannot drill through it without damaging it beyond usefulness, then it’s probably time to repour it.
All Things Considered
Drilling holes in a concrete fence post is a troublesome job but not altogether impossible. It will take a lot of patience and repetition. Even if you do everything right, it may still be damaged beyond repair.
However, it’s one of those problems where (what do you have to lose?) is a viable question. You can either effectuate the repair or you can’t and you’ll have to pour a new post.