How to Complete a Concrete Cut for an Egress Window

In many egress window installations, cutting a larger opening into the foundation of your home will be necessary in order to install a window that is large enough to pass the local building code. If you are completing this project DIY-style, you will want to follow the 10 step process outlined in this post.

Before you begin, please be aware that cutting the concrete in your foundation can be a daunting and dangerous task. If it is done incorrectly it can cause structural damage to your home or injury to yourself and others.

If there is any part of the egress window installation process that we recommend hiring a professional for, it is this. Please only attempt this on your own if you are fully confident in your abilities and have taken all necessary safety precautions.

* This post is intended as a guide only. The Great Egress Co cannot be held liable for any damages or injury caused as a result of these instructions. Always consult local building code and obtain proper permits.

If you are confident in your abilities and have taken all the necessary safety precautions, the 10 steps below outline the process you should follow.

1   Mark the window outline from the inside.

Outline the dimensions of the window on the wall to give you a sense of its size and location. Since concrete cutting is not as exact as wood cutting and to provide additional space for installing a wood frame, you will want to mark this about 3 ½” wider than the rough opening required by the window dimensions and allocate an extra 1 ¾” to the height. Also, be mindful of whether you will need allocate additional space to install a header support beam. This will be the case if you are cutting a new hole in a load-bearing wall or if the hole is particularly wide.

2   Build a temporary support wall.

If the window cut you are making will require a support header, you will need to construct a temporary 2”x4” support wall to hold everything in place while you work on the project. The support wall should be approximately 3’ back from the wall being cut. Align the vertical studs directly with the floor joists. Ensure that you measure and cut each stud for a tight fit.

3   Hang plastic to contain dust.

Cutting concrete is a dusty and messy process. You will want to hang plastic to contain the dust as best as possible.

4   Drill hole through Centerlines.

Locate the centerlines on both the top and bottom of the window outline. Using a ½” x 16” masonry drill bit, drill a hole through the wall on the centerline of both the top and bottom of the window.

5   Mark the window outline from the outside.

Mark the rough opening of the Egress Window on the outside of the foundation wall using the two holes drilled through the wall as the centerline of the vertical window opening and the top and bottom of the horizontal opening. Use a long level to measure the dimensions and ensure that they are level. Mortar lines in the foundation wall can also help serve as a level reference.

6   Drill Holes at each corner.

With the corners marked, you can drill a level hole through the wall at each of the corners.

7   Cut the concrete.

Beginning on the outside, cut the concrete will with a diamond blade concrete demolition saw. Begin by cutting a ½” deep groove in the concrete block, and then finish the cut on a second pass. After cutting from the outside, proceed to cut from the inside. Expect a tremendous amount of dust when you cut the concrete. Wear all necessary protective equipment like goggles and a mask. Wetting the saw blade can help reduce some of the dusk. We recommend using an electric saw rather than a gas saw so you do not have to worry about fumes while completing the cut indoors. Ensure that you plug the saw into a GFCI outlet to prevent against electric shock, particularity if you intend to wet the blade to limit dust. 

8   Knock out the block.

Break out the cut block with a 3 or 4-lb. hammer, starting at the top center. Work carefully around the edges so you do not loosen the remaining blocks. For stubborn blocks, first break out the core in the middle of the block, then break the block.

9   Smooth out the opening.

Using a brick chisel, chip the sides of the opening until they are smooth. Double check the measurements to ensure that the opening is large enough for a frame and the window.

10   If you have a block foundation, fill the block cores with concrete.

The blocks along the bottom of the cut will need to be filled with concrete. Before applying the concrete, you will want to stuff the cores of the blocks with newspaper to prevent the concrete from dripping down.

Conclusion

There you have it, 10 steps to completing a concrete cut for an egress window. Once again, we cannot stress enough, if you are not 110% confident in your abilities to complete this, don't even attempt it yourself. Hire an expert help. Cutting into your foundation can be dangerous and can cause structural damage to your home if done incorrectly. That said, if you know your up for it, grab your tools and safety equipment and get cutting.