The process of enlarging basement windows

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The process of enlarging basement windows to bring them up to code. 

If you have an older home with a basement, you probably have smaller windows in that basement. Have you ever thought of changing them?

If you’re expanding your living areas into your basement (finishing a basement is always worth it!), you’ll need to think of safety as well.

What if there was an emergency and you needed a quick way to escape the basement?

In this case, you can replace those tiny old windows with larger ones to give you easy access to outdoors.

Here is the process we used to enlarge our basement windows.

new opening for egress window

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*** FIRST be sure to check your local code to see what size of window you need***

After checking our local code, we decided to lengthen the current window by replacing it with a casement window (the one that swings open completely).

We cut the window opening ourselves because our foundation is a type of cinderblock and the cuts would be neatly along the joints of the block. IF we had a concrete foundation, we would have hired it out. And just to give you an estimate of the cost (because I collected bids), you would be looking at $300-$400 per window.

Since our foundation is cinderblock, I had to patch below and around the window with concrete.

Now that you have the details of what we were working with, let’s talk about the process.

**Project DISCLOSURE** We are not experts, just homeowners learning about remodeling and sharing our projects with you. The projects, suggestions, and tutorials on this site are not error-proof. They are simply what worked for us or in some cases, what did not work. Additional research and precautions are always recommended.


Let’s break this down into the steps we took:

  1. The first thing you should do is order your new windows. We also ordered window wells and everything took about 2 weeks to casement window for basement
  2. As you probably know, you need to dig out the dirt around where your new window will be. To make it easier for your cut, you will need a hole that is 1-foot wider on all sides of where your new window will be. Plus, you need a 4-foot projection (the distance from the foundation to the dirt).
    • Here are our before and after of our digging:old basement windowhole for expanding basement window
    • P.S. My husband hand dug each hole and it took about a week for both holes; this was after work and one Saturday.
  3. A couple of days before our scheduled cut day, we removed the old windows and cover the area with plastic to help prevent dust from getting all over the house. We made sure to leave room to cut the window opening inside this plastic in each room.


Before cutting, we made a level line of where the cut should be. Later, it was hard seeing the lines once the dust started.

When we started cutting, we encountered another challenge. We used an electric concrete saw but the saw only cut 8″ thick foundation (which is a standard foundation). Our foundation was 10″ so we had to cut from both sides (inside and outside of the window).

concrete saw

Luckily, my dad has experience with this so he came over and made the cuts for us. 

SIDE NOTE: Gas-powered concrete saws can have water dripping next to them to help minimize the dust.

cutting basement window

Once the cut was made on both sides, we used the sledge hammer to get the first block out. After that, they all came out very easily.

removing cinderblock for window

Here is what we were left with:

expanding basement window
installing egress window


Next, we placed the window. To make cutting easier, we had cut to the next block end, which meant we had about a 4″ gap. So, we cut two treated lumber pieces to set the window on. We made sure the window was level and used shims to prevent the window from moving.

installing casement basement window
setting new window

Then we created a concrete form using 2×4’s, wiring them together.

concrete form around window
concrete form around window

After, I mixed some concrete and filled the forms.

Once the concrete had dried, at least 24 hours later, I removed the forms and cut the wire as close as possible to the concrete. 

Next, I caulked the outside of the window (cutting down the shims with a razor, if needed) and adding spray foam to some areas of the inside. See a more detailed tutorial on the process we use to install basement windows here.

installing new egress windows in basement

And now, we have new windows that are up to code for our area. Let’s see a before and after:

old basement window
new window well installed

Hope this will help you know what you need to do to expand your basement windows.

P.S. Be sure to stay tuned for how to install a window well.

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