How to Drill Into Concrete

A builder drilling holes into concrete for bolt anchors

There’s a bit more to drilling a decent hole in concrete than cutting through wood or metal. In fact, the process is quite a bit different and there are a few things to consider which don’t apply to drilling other materials. If you’re ready to learn how to drill a hole in concrete, then let’s dive in and we’ll give you the knowledge you need.

Things to You Need to Know for Drilling Into Concrete

Before we get into procedure, you’ll need to have a few things in order. Without these, you could be in for a rough time. 

How Long to Wait After Concrete is Poured

Unfortunately, you can’t just drill into fresh concrete as soon as the surface is dry. You’ll need to let it cure properly for the best results.

It’s always best to wait at least 3 days before drilling. New or ‘green’ concrete can be prone to cracking if drill before it has sufficiently cured. 

If you’re planning on using wedge bolts, or any other type of anchor which expands in the holes, using friction to hold them in place, then you’re best to wait a full 28 days to ensure no cracking will occur. 

If you don’t have this kind of time to wait there are a couple of options available. Epoxy anchors are available where an epoxy resin is used to set the anchors into a hole. As there is no expansion of the anchor to create stress in the green concrete you’re unlikely to get any cracking. 

Another option, if you know you’re going to need anchors in the concrete in the first place is to set the anchors in the concrete when you pour it. While this isn’t always possible, if you can do it this way you’ll always get a better hold than any choice of anchor which requires drilling. 

Selecting the Right Drill

The right drill is important. Depending on the diameter and depth of holes you’ll need to drill you’ll need a drill with enough power. Bigger holes will require more power. 

Hammer drills are ideal. They have a different mechanism than a standard drill, providing an impact force along the axis of the drill while rotating. The hammer action is ideal for drill hard but brittle materials, chipping away and increasing the penetrating power of the drill.

While it is possible to drill into concrete with a standard power drill, if you plan on drilling a lot of holes in concrete, it’s worth it to add a hammer drill to your arsenal. 

Selecting the Right Drill Bits

There’s only one right way to go when drilling through concrete: masonry bits.

Masonry bits are always labeled as such, but if you just have a box you’ll need to recognize them. They’ll look mostly like any other screw bit, but the head is slightly wider than the shaft, which clears the way so the shaft fits right as it goes through the material.

Most of the cutting is done by the head, with the flute pulling debris. In a hammer drill, the head is repeatedly slammed into the concrete, breaking it up quickly so the dust can be carried away by the flutes.

Masonry bits are usually made of HSS with a coating. The very best are made from solid carbide, but a set of carbide tipped masonry bits will do the job. Cheap masonry bits will burn quickly when drill an abrasive material like concrete and should be avoided.

The correct size is determined by your fastener. The drilling size will be specified by the manufacturer and should be easily found on the box.

Dust Management 

Dust from concrete is both obnoxious… and dangerous if proper precautions aren’t taken.

PPE is always the first line of defense. In this case, you’ll want some form of mask that actively filters the air. The usual white dust mask isn’t sufficient here. The respirator or other PPE shouldn’t be the only thing you do, however. It’s mostly there before the rest of your precautions are in place.

Use a good dust control system while drilling masonry or concrete as well. Reduction of airborne dust will help prevent any damage which can occur during the working process. The collection system should be M-rated to protect you from the fine dust.

You can also drill wet, which will turn the dust into mud instead of flinging it airborne as long as there’s sufficient water to the drill. It’s not required, but it keeps the bit cool and the airborne dust down.

So, why do we go through all of these precautions for “a little dust”?

The answer is a condition called silicosis. Concrete, bricks, and many ceramic materials all contain silica in one form or another and the ultra-fine dust released is a hazard.

There is no cure and each time you’re exposed to silica dust you get one step closer. It’s caused by small silica particles landing in the lungs, causing an inflammatory response and eventually a chronic respiratory condition.

Always manage the dust when drilling masonry, concrete, or stone. Otherwise, you’re putting yourself at risk of more than just an extensive cleanup. 

Step-by-Step Guide: How To Drill Into Concrete

So, with the above in mind, we’re ready to get going drilling some holes! Let’s go through the steps required to make the job easier for you.

Safety First

In addition to taking care of the dust which arises during the process, you have a few other hazards to watch out for while you’re drilling. Be aware of them before you start your tool.

The big ones are:

Kickback- If you’re using a standard drill, it may seize up and kick back on you. The best way to avoid that is to use a hammer drill, but in any case, you need a firm grasp on the drill. A side handle is best, if not available hold it steady from the top. Kickbacks are usually just surprising, but they can cause injury so be alert. Even the best hammer drill can bind in the right circumstances. Keep a firm grip with two hands.

Unseen Obstructions- There may be some obstructions in the concrete. Always plan carefully beforehand to avoid things like pipes and wires that may be hiding out of sight. Consulting the plans for the building helps, but the best solution is renting a GPR(Ground Penetrating Radar) to give you the right picture. They can be rented and they can be lifesavers.

Know where you’re drilling, and use good practices while drilling and you’ll be fine.

Make sure you also have ANSI-rated eye protection on while drilling. Specially designed drilling gloves aren’t a bad idea, but they’re not necessary for small jobs.

Drilling concrete can get pretty noisy. If you’re planning on doing a lot of it hearing protection is also a good idea.

Mark the Surface 

First, you’ll want to mark the centers of each holes you need to drill. 

For most applications, a simple mark will do. Concrete is easy to mark and anything from a carpenter’s pencil to a spare piece of chalk will do.

Check as best as you can on the other side of the concrete. Depending on your placement there can be anything from pipes to wiring on the other side. None of which you want to hit since they’ll make the job much more difficult.

As always, measure twice cut…or drill…once.

Prepare the Drill

Next, set up the drill. Starting with the speed. 

As with drilling all types of material the smaller the drill bit the faster you’re going to need to run the drill. Conversely the bigger the drill bit the slower you’re going to want to run it. It’s hard to put specific values on this as it will depend on a few factors like the composition of the concrete and the quality of your drills. 

It’s always tempting to run the drill as fast as you can as this will speed up the rate at which you can drill holes. However you will burn out your drill bits if you’re not careful. Finding the right balance is something that will come with experience. 

Lastly, set the depth stop bar on the drill. For most anchors, you’ll want to be ¼” longer so there’s a little bit of clearance. 

Get in Position

Position yourself over the area you’re planning on drilling, or beside it if you’re drilling a wall.

For drilling downwards, get on your knees in a stable and comfortable position. Knee pads will make things easier, particularly if you have to handle multiple holes.

If drilling into a wall instead of a slab, stand in a stable position where the drill can easily reach the wall.

In both cases, grip the drill like a pistol. Preferably like a large one that’s about to kick. Your off-hand should either be on top of the drill or holding the side-handle firmly.

Drill a Pilot Hole

First, you’ll need a smaller hole to help guide you.

While in position, go in exactly perpendicular to the wall or floor with the bit. A depth of ¼ inch to ½ inch deep is sufficient for creating this initial hole.

Apply only light pressure to the drill. Pressing it in hard enough to slow the drill doesn’t help, it just burns bits faster. 

If you have the option to turn off the hammering function on your drill this can be a handy tip when you first start the hole. The hammer function will make the drill bit jump around a little and it can be hard to keep it on the center mark. 

Don’t neglect this step. It’s a bit more work to change the bits out, but it’ll help to ensure each holes is accurate to your center mark. Afterward, clear the dust from the hole and switch to the bit for your fasteners if you use a smaller bit to make the guide.

Drill Hole to Size

Now you’ll put the properly sized bit in your drill, and continue through the concrete with it.

Two things are majorly important here:

  • Maintaining a good grip on the drill
  • Keeping the drill perfectly straight into the hole

This is going to take some time, and you can’t just grind on the drill the whole time. Keep the speed sensible and avoid the temptation to “lean” on the drill. Too much pressure will overheat the bit and can even cause the drill to bind.

You’ll also need to back the drill out repeatedly to allow it to get rid of concrete dust. Back the drill out every 10-15 seconds and allow the flutes to clear. It makes the whole process more efficient.

Pay close attention to the drill. Any change in noise or feel may indicate an obstruction, which you’ll have to clear before continuing.

Drill until you’re at your desired depth, dedicated by the depth stop you set earlier. 

It’s not a bad idea to also keep the area wet while you’re working. It helps keep dust down and extends the life of bits. Even something as simple as a spray bottle works.

Clearing Obstructions

Most obstructions are easy to clear.

Just take a long masonry nail and a hammer and insert it into the hole. Tap on the back until you feel it break loose, then try again with the drill.

Don’t tap the nail into the obstruction all the way. Just use it to break up whatever is causing problems then get back to drilling. It may take a few tries depending on how things go.

There’s one exception to this: watch the nail as best as possible to see if it sparks. If it does then you’ve likely hit some of the supporting rebar in the wall or floor. You’ll need a rebar cutting bit to clear it in most cases.

Work cautiously and remove obstructions as soon as they arise. 

Clear Dust and Debris

After the hole is done, you’ll need to clean it up before you fit the fasteners.

You’ll need a shop vac of some sort, although you can brush the surface debris away easily enough. A HEPA filter is ideal, although it’s not required.

Run the vacuum and pull the dust from the hole. Try not to blow into it, especially if you did it dry since that will cause the noxious dust to go airborne.

Dust management is the name of the game here. It’s safe to work concrete with the proper precautions, but they have to be taken every time.

Final Word!

Hopefully, you don’t find the above intimidating. Learning how to drill in concrete often seems much harder than it is, but it’s an easy process when you know what you need to consider. It’s just a matter of carefully moving ahead. 

Practice makes perfect, so why not get started on learning this valuable DIY skill?

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