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The process of enlarging basement windows

If you have an older home with a basement, you probably have smaller windows in that basement. And maybe you are looking at enlarging those windows because no one could get out of that window if they had to. We had this problem with our basement windows and decided it was time to solve the problem. Here is the process we used enlarging our basement windows.

new opening for egress window


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  • new windows
  • plastic
  • safety glasses
  • face mask
  • shims


Find the list of tools we use.


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

After checking our local code, we decided that we would be able to lengthen the current window by using a casement window (the one that swings completely open).

We decided to cut the window opening ourselves because our foundation is a type of cinderblock and the cuts would be right 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 got bids), you would be looking at $300-$400 per window.

Because 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 move to 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 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. Ours took about 2 weeks plus we ordered the window wells too!new casement window for basement
  2. As you probably know, you need to dig out the dirt around where your new window will be. If you are hiring a company or 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 there was room to cut the window opening inside this plastic in each room.


We used an electric concrete saw but another problem was that the saw only cut 8″ thick foundation (which is a standard foundation). But our foundation was 10″ so we had to cut on both sides (inside and outside of the window).

concrete saw

Because my dad has experience with this he came and made the cuts for us. Before cutting we made a level line of where the cut should be. But it was hard seeing the lines once the dust started.

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

cutting basement window

After the cut was made on both sides, the sledge hammer was used to get the first block out. Then they all came out very easy after that.

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 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 if needed with a razor) 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.

before and after of egress windows

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!