Replacement basement windows can be added to concrete walls, but before a new window is installed, the old basement window needs to be removed along with the cement holding it in order to create a leveled surface. Pressure treated wood may be installed around the opening using special screws. Then replace the cement around the window to more easily fit the wooden frame in line with the concrete. This cement also keep out water that may have gotten into the window. With this step completed, you are now able to install the replacement basement window using the right measurements.