Whether you are installing Andersen casement, double-hung or gliding windows, please follow all of the manufacturer’s instructions and recommendations.
Prepare your opening. From the exterior of your home, cut the rough opening for the window out of your house wrap. Fold in the sides of the house wrap, staple or tack them down, and tape the top to the inside of the home.
Apply the self-adhesive flashing to the sill area, and either nail or staple the corners down. Flashing will keep rain running down the window instead of getting trapped inside the house. Set your shims, or spacers, on the sill where your side jambs (wood trim) will go, and silicone the perimeter of the rough opening.
Place the window into the opening. Nail one of the top corners of the window to stabilize it, and shim the sides. Check for plumb, level and square as you are shimming until it is within 1/8-inch of being level. Using nails, attach the window to the rough opening through the nailing or windbreak flange. The flange is a flexible vinyl strip that goes around the perimeter of your window that allows the window to be put in and stops water from infiltrating the house.
Seal the exterior of your window. On the exterior of your home, place flashing on either side so that it overlaps your sill flashing. Silicone the top of the window on the exterior, and apply the drip cap, a lip that will stop rain from running directly onto your window. Place your top flashing over the lip of the drip cap, and flash the top of the window, making sure to overlap the side flashing. Fold the house wrap over the flashing, and tape it down.
Cut your side and bottom shims flush with the unit. Apply your insulation to the interior and exterior of your home on all four sides of the window, and place a line of silicone around the perimeter. If your wall’s thickness demands the use of extension jambs to trim around the window, the nice thing about installing Andersen windows are the unique, grooved extension jambs that allow for a perfect fit for your trim. Andersen also offers a similar product for the exterior if you are using a standard sized window in a non-standard sized hole, that will let you trim out the window and fill in any gaps you may have.
Things You’ll Need
- Staple gun
- Self-adhering flashing
- Waterproof shims
- Silicone caulk
- Caulk gun
- 4-foot level
- Roofing nails or deck screws
- Backer rod weatherstrip
- Safety glasses
- Tape measure
- Putty knife
- Utility knife
- If you are using a low-expanding foam for insulation, or to fill in a larger rough opening, allow some gaps at the bottom rail to allow for water migration.
- If you have a friend who is a contractor, ask them to oversee your installation project.
- Use safety precautions in lifting, tool usage and installation of your window.
- Only use a very-low-expanding insulating foam for this project. If you use anything else, you run the risk of installation that is too tight, potentially causing operation problems.