How to Install Replacement Windows

It couldn't be easier to learn how to install replacement windows. Replacement windows are a simple way to improve the look and energy efficiency of your home. Insert replacement windows are designed to fit in your existing window opening without removing molding or exterior trim.

Before You Buy Replacement Windows

Before you order your replacement windows, you'll need to carefully measure each window opening to be replaced.

First, measure the width of the opening from the inside jamb on one side, to the inside jamb on the other side. You'll want to take this measurement in three places: near the bottom of the window opening, in the middle of the opening and near the top of the opening. Use the smallest measurement to order your window.

Next, measure the height of the window opening, from the top of the sloped sill to the bottom of the window's head jamb. Take this measurement in three places: near the left side of the window opening, in the center of the opening and near the right side of the opening. Use the smallest measurement to order your window.

Finally, measure the angle of the slope of the sill using a protractor or other angle measurement tool.

Install Your Replacement Windows

To install your replacement windows, follow these steps:

• Remove the stops. You window will have two vertical wooden strips that hold the window in place called stops. Carefully remove the stops if you plan to reuse them.
• Remove the inside sash. Tilt the inside sash toward you and remove it. On older windows, there may be a sash cord or chain; cut and remove these connectors.
• Remove any parting beads. Parting beads are plastic or metal strips that rest between the sashes. Remove the parting beads and discard.
• Remove the outside sash. Slide the outside sash to the bottom of the window and remove it in the same way as you removed the inside sash. Some windows may have a vinyl or metal jamb liner-remove and discard these.
• Clean up. Clean any loose debris from the window jamb and repair any screw or nail holes with wood putty. DO NOT remove the outside stops-these are used to hold the replacement window in place.
• Prepare the opening. Apply a bead of elastomeric caulk along the inside edge of the outside stops and the blind stop at the top of the window. Apply caulk to the outside edge of windowsill as well.
• Insert the in window. From inside the house, insert the bottom of the replacement window into the opening so that it rests against the sill. Tilt it up and press it tightly against the outside stops.
• Position. Loosely attach the window with a single screw. Make sure the window is plumb and sits square in the window opening. Use shims between the window and jamb as needed. Cut the excess shims off with a utility knife.
• Attach the window. Fix the replacement window to the jamb using wood screws through the pre-drilled holes.
• Finishing up. Inspect the outside of the window and caulk any outside gaps. On the inside, fill any gaps with minimally expanding insulation foam and reinstall the inside stops. Caulk any gaps left by the stops and prime and paint as needed.