Installing a replacement window involves replacing the sill, installing the top and bottom sashes as well as the header, and then placing the replacement window in the opening. Windows are measured before final installation, and the header covers any gap between the window and frame. Use adjustment screws and side jambs to ensure correct window placement before caulking the inside of the window and reinstalling the interior stops.
Installation is typically done from inside the home. Replacement windows fit inside existing frames, so the sashes, parting bead and inside stops are first removed. Cut the sash cords or chains to remove the sash. Slide the outside sash from the bottom of the window and remove the parting beads. Leave exterior stops in place to retain the replacement window. Clean sills and frames thoroughly and repair any cracks or holes with caulk before installing the new window.
Install the new sill using caulk after measuring the sill angle. Measure and center the top and bottom sashes vertically within the frame and then slide the bumper stop towards the center of the frame until the mounting holes are visible. Install the mounting screws along the top and bottom of either side jamb after positioning the replacement window. Poorly adjusted or improperly installed windows may become damaged or fail to open and close easily.