Even if your house sits quite a bit lower in the ground with barely any basement wall exposed, it is still possible to install a light-bringing window by re-grading the soil along the basement wall on the side of the house. If that is impractical or too expensive to do on a large scale, then you can dig a window well. It is important to remember, however, that the grade at the bottom of each window is at least 4 to 6 inches below the window frame, so that rain water and melting snow can drain away from, rather than leak in, the sill. The same rule applies to your yard around the basement wall — allow sufficient space below the window frame for drainage.
An experience do-it-yourselfer can complete the job him—or her—self using the following steps. Depending on your available time and personal skill set, it may be easier and less frustrating to hire a professional to take it from here. With that caution in mind, here are the steps to follow:
You should wait until you have the actual window in hand before making the opening. If building your own custom bay window, it should be completed in advance so you can make the frame and opening to match. A stock window does not need to be double hung, but a casement window will be easier to open. Pre-assembled, ready-to-install bay and bow windows are also available in standard sizes. You may want to consider these before making the rough opening, or before building your own.
After your window location has been scouted out and the yard graded and lowered, create the opening for your window. All windows fit within a rough opening in the wall framing, so you will need to measure and mark where this opening will be. This rough opening is slightly larger than the overall dimensions of the window, measured at the outside edge of the jambs, and the extra space allows the window to be plumbed and leveled as needed. With a purchased standard window, there will be instructions for the size of the rough opening you will need to make. In this basement example, the measurement should be the dimensions of the window plus 2 additional inches. These extra 2 inches are for the wooden frame you will be building into the opening to attach the actual window to.
Always be sure to have the following safety items available for your protection: safety glasses, gloves, and a proper dust mask or respirator.
If your basement wall is made from cement block, you can break through it with a cold chisel and hammer. If your foundation wall is made from poured concrete, then a power chisel or a rented jackhammer should do the trick.
After the opening has been made, smooth the edges of the hole and butter those edges with a stiff mortar mix. Next, set in a 3-sided wooden frame of at least 2-inch-thick lumber that is as wide as the cement block or concrete is thick. The existing horizontal house plate that contacts the concrete basement wall from the floor above can serve as the top of the frame and the fourth side if your window is high up on the basement wall. Otherwise, make a 4-sided frame.
Plumb and level this frame while the mortar is still wet. This is the rough opening itself.
After the mortar has dried, set the window into the frame, line it up flush with the outside edges of the frame and carefully nail it into the 2 inch rough frame on all sides. Depending on how the window was built, you may be able to drive the nails into the rough frame parallel to the wall if it is a wood frame window, or, if it is in a metal casing, there will be a flange or edge you can use to nail perpendicular to the wall into the edges of the rough frame. Other possibilities exist; use your window as a guide if no instructions came with it or if it is custom built.
After it has been nailed into place, use narrow wooden trim on both the inside and the outside to surround the window and hide the attachment framing. You may want to put a small bit of insulation around the framed window before applying the trim, to lessen heat loss through the frame.
Note: If you live in an area that gets snow, check the snow level around the basement wall and window. Snow that has melted near the wall or window indicates heat loss. If this occurs, you may need to remove the trim, re-install your insulation and seal it a bit better.