How to Drill Large Bore Holes Into a Brick Wall (and How Not To)

For installing ventilation pipes, I needed two large bore holes through a brick wall. Here I would like to share what did not work, so you do not have to try it yourself, and how I eventually got through the wall and what I learnt while doing it.

Core drill (rental)

Diamond core drill bit (rental)

Eye protection

Ear protection

Gloves

I wanted to install a ventilation system in the basement and had to get two holes through a 20 cm brick wall to pass through the pipes. One pipe for fresh air intake, the other pipe for used air exhaust. The pipes I am going to use for that are 125 mm PVC underground drainage pipes, those standard orange ones, as I have seen other commercial providers also using those for the part where the ventilation system runs underground.

Furthermore, I also wanted to pass a 20 mm water pipe through a third hole to install a water tap in the front yard.

Disclaimer: Those holes were to be made not directly through the house wall, but lateral into the basement light well. Therefore, I had no concerns regarding the structural stability of the house wall itself. If such holes are to be made through a supporting wall, it might be wise to consult a structural engineer beforehand.

As I wanted to pass 125 mm pipes, I opted for a 150 mm hole to have some whiggle room and to leave enough space for fixation of the pipe within the hole and for waterproof sealing. Initially, I wanted to use my own rotary hammer drill and bought a simple 150 mm core bit as seen in the picture, as those a specifically sold for that purpose. However, I failed miserably and maybe got a centimeter into the wall before I gave up with that setup as there was only minimal progress and the machine was already cooking.

As I also had to get the water pipe through that wall, I gave it a try with my rotary hammer drill and a simple 30 mm core bit, which I already had from a previous project, and that worked out well. It took some effort for the machine, but in the end I could get through the wall.

I inquired with several professionals and they were asking for €300+ to come by and get those two holes through the wall, so I looked further.

There are many videos online that depict how to get a large bore hole through a wall without using professional equipment, and usually that is done by drilling many small holes through the wall (maybe using some kind of guide), and then taking out the brick material using a hammer and a chisel, or the hammer drill with a chisel. I have not tried that myself but it all looked like a lot of messy work, tricky to be done at all when you can attack only from one side, and without the guarantee to get a smooth hole in the end.

Thus, I looked further around and was happy to see that a local hardware store was actually renting out professional core drills along with diamond core drill bits. If you can find that also somewhere in your vicinity, I would highly recommend to go with that option, which I will further delve into in the next step!

From the hardware store I rented a professional core drill along with a 152 mm diamond core drill bit. The rental guy ensured me that - for brick walls - for up to a 162 mm drill bit you can do it freehand, without a tripod. And also that it could be done dry, without using a water connection. (Concrete walls, however, are a different beast!)

At first I did not know what to expect from such a heavy machine, but you quickly understand how it wants to be handled and then it is a breeze!

My learnings:

Wait for the drill bit to reach full speed before you attack the stone. The drill bit turns quite fast, and similar to drilling through metal, you use the speed and only moderate pressure.

The machine I got actually reduced the speed or switched off when the resistance became to high, probably to avoid that the drill bit gets tilted and stuck. Thus, you need to keep the machine steady and fully in line with the hole.

After approx. each centimeter progress, pull the drill bit back and forth (not out) while it is turning to clean out the drilling dust from the hole. If that is not done regularly the drill bit gets stuck.

As the machine is heavy and needs to be kept properly aligned with the hole, it takes some strength to get through the process (or simply some breaks).

The machine and the drilling is obviously pretty loud, so proper ear protection should also be obvious. An even bigger concern is the debris produced by the drilling. There were no bigger pieces flying around, but the amount of fine dust produced is tremendous and I certainly could not have done it without some protection googles that close around the eyes. And you certainly will require a shower afterwards!

When you are done and you need to get the core out of the drill bit, hold it downwards, power it up, then release the power button and - while the drill bit slows down again - lightly tap with a hammer to the side of the drill bit and the core will fall out.

After I got the hang of it, drilling those holes was really fun and it took me less than 10 min for each hole. And on top, they just turn out perfect! All in all, picking up the machine, drilling those two holes, taking a shower, and dropping off the machine again was done in under two hours and set me back €95, which I was happy to invest considering the alternatives ;)