Adding a window not only allows light into a dark basement but can improve the value of your home. It’s hard work, but cutting out a window in a concrete basement can be done in a weekend. Your new window can also help you and your family escape in case of an emergency.
Preparing to Cut
Excavate the soil from the exterior wall. Dig a hole a minimum of six inches deeper and wider than the window you plan to install. If you’re installing an egress window, check your local building codes and secure a building permit. Most municipalities require a window with a height of no less than 24 inches, a width of no less than 20 inches and an opening of at least 5.7 square feet. On the interior of the wall use a grease pencil to mark the dimensions of the window. Add three and a half inches to the horizontal measurements of the window and an inch and a half to the vertical measurements to accommodate a pressure-treated wood frame. For an egress window, the bottom of the window cannot be more than 44 inches from the floor. Use a hammer drill with a masonry bit to drill a hole completely through the wall at the lower corners. Keep the drill level so the exit point of the bit will be at the same location on both sides of the wall. Mark the top two corners and make sure your opening will be square by measuring between opposite corners. If the distance is the same, drill through the top two corners. Use a chalk line or level to mark where you’ll be cutting on both sides of the wall. Sawing concrete is very dusty, so secure tarps around your work area inside to contain the dust.
Cutting the Concrete
Most basement walls are made from concrete blocks, though more recent construction may feature poured concrete walls. You can rent an electric concrete demolition saw at larger hardware stores. They’re available with 12- or 14-inch blades. Most walls are eight inches thick and a 12-inch blade will work well, but upgrade to a 14-inch saw if your walls are 12 inches thick. A diamond blade is more expensive but will cut more than twice as quickly as the stock blade. Always wear heavy gloves and eye, ear and lung protection when operating the saw. Score your cutting line first on the outside of the wall, then the inside, and knock the pieces out with a four-pound or heavier hammer. A poured concrete wall will be extremely heavy; consider leaving the heavy slabs to a professional. If you choose to do it yourself, make additional cuts about a foot apart to keep the pieces smaller and more manageable. Use a masonry chisel to square your corners and smooth out uneven cuts to prepare for building a frame for your window.