Core drilling through concrete, cinder block, or concrete masonry units (CMU) is usually something that is required whenever you are installing a dryer vent or exhaust fan in a basement. Although drilling a hole in a concrete or cinder block foundation requires some specific tools, it is generally a pretty straightforward project that the average homeowner can tackle.
To core drill though concrete of cinder block, start by marking the location of the hole on the foundation wall. After marking the location for the hole, use a rotary hammer and a diamond blade hole saw bit to core through the concrete or cinder block. Apply steady, even pressure as you drill all the way through the foundation wall.
Before core drilling though a concrete or cinder block foundation wall, it is highly recommended that you consult with a structural engineer to ensure that you are not drilling a hole that may compromise the structural integrity of your home.
With that said, let’s take a look at how to core drill through concrete (or cinder block) in detail.
Tools and Materials Needed to Core Drill Through Concrete or Cinder Block
To successfully core drill through concrete or cinder block, you will need the following tools and materials:
- Safety Equipment (Glasses, gloves, boots, ear protection, etc.)
- Rotary Hammer (or hammer drill)
- Diamond Core Drill Bit
- Core Drill Bit to SDS Hammer Drill adaptor (if needed)
With all necessary tools and materials on hand, you can now begin coring through your concrete or cinder block foundation.
How to Core Though a Concrete or Cinderblock Foundation Wall
1. Mark the Hole Location on you Concrete or Cinder block Wall
The first step in coring through a concrete or cinder block foundation wall is to mark the hole location on the wall. If you are core drilling through a concrete foundation wall, this is as simple as marking the hole location wherever you want.
If you are drilling through cinder block, however, you want to ensure that you are are drilling through the hollow (annular) space in the cinderblock, NOT the structural components. See below.
After appropriately marking the hole location on your concrete or cinder block foundation wall, you can begin drilling your hole.
2. Core Drill Through the Concrete or Cinder Block Foundation Wall
In order to core drill through a concrete or cinder block foundation wall, you will need a rotary hammer (or hammer drill) and a diamond tipped core drill bit. Select a core drill bit that is appropriately sized for your application. In my case, I used a 4.25″ core bit to accommodate a 4″ exhaust fan duct.
If your core drill bit is equipped with a pilot bit (small drill bit in the center of the core bit), place it on the mark and begin core drilling though the concrete or cinder block.
If your core bit does not come with a pilot bit, I recommend that you use a brace (as shown below) to prevent your bit from moving around as you start your hole.
Getting the core drill bit started is typically the most difficult part of drilling though concrete or cinder block.
Continue drilling through the concrete or cinder block foundation wall until you reach the other side.
PRO TIP – Ensure that you use appropriate PPE (Respirator, Eye Protection, Ear Protection, Gloves, etc.) when you are core drilling though a concrete or cinderblock foundation
Depending on what kind of core bit you are using, take care to ensure that your drill bit does not overheat.
After drilling through the concrete or cinder block foundation wall with your rotary hammer and core bit, you will be left with an opening that looks like this:
Clean up any dust or debris resulting from core drilling through the concrete foundation wall.
3. Install Exhaust Fan, Dryer Vent, etc. to fill the void in the Concrete or Cinderblock Wall.
After Core Drilling through the cinder block or concrete foundation, install your exhaust fan, dryer vent, etc. as needed to complete your installation. Seal any gaps with spray form or caulk.
At this point, you have successfully core drilled though a concrete or cinderblock foundation wall.
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DISCLAIMER: This is a reference guide only. Consult a structural engineer before performing any work on your foundation.Attempt at your own risk. Links included in this article might be affiliate links. If you purchase a product or service with the links that I provide, I may receive a small commission. There is no additional charge to you! Thank you for supporting ATimprovements so I can continue to provide you with free content each week!