How to Install Replacement Windows
Old drafty windows can increase your energy bill and make your house less comfortable. Learn how to install replacement windows in this Lowe’s video:
For project details and a tools and materials list, click here.
You have two choices with window replacements: full replacement or insert window replacement. For a frame that’s in good shape, you can go with an insert window (also known as a pocket window), but when the existing windows are old and failing, a full replacement down to the house framing is best.
To get the right size window, measure the height of the pocket opening, which is the frame of the actual window, not the stops. The new window must be 1/2 to 3/4 inches smaller than the opening. Check the manufacturer’s directions for specifics for your windows.
When you’ve bought your new window, you can remove the old sashes. Windows are built differently, so the steps needed to remove yours may vary. Sometimes it’s best to remove the sashes from the inside; in other cases, it will be easier to work from the outside.
If you have a storm window, remove it first. You might have to score the paint, then take out the screws. Remove the sashes if you can, and pry out the frame. If you have side sash springs, carefully remove those. From the outside, remove the exterior sash stops using an oscillating saw or a hammer and chisel. Take out the upper sash, then remove the middle parting stop and remove the lower sash. Leave the interior stop. Make sure any holes are filled or that there is good existing wood where the new window will be screwed into the frame. Replace any damaged or rotten wood. Clean the opening to remove all the dust and debris.
With the sashes removed, the frame is ready for our replacement window. Apply flashing tape to the sill; it should fit the length of the sill. Extend the tape up the vertical leg of the stool (the bottom ledge of the interior side of the window) and work the tape into the corner, then check the sill for level or bowing. Place and level the sill shims if needed to correct for any bowing. It’s important to place the shims correctly to ensure proper leveling. Attach the shims with flashing tape to prevent any further movement once they are level.
Now dry fit the window into the opening. You should have a little gap around the frame. Then set the new window aside.
Apply a 3/8-inch bead of sealant at the interior head and jamb stops and sill. Place the window in the opening, resting it against the interior stops and making contact with the sealant. Install shims at the pre-drilled holes in the frame, then drive screws through the holes and the shims. Add shims at the ends of the meeting rails as needed to be sure the sashes sit evenly within the frame.
Check for plumb, level and square to be sure the window operates properly. You can make any additional adjustment with shims. When everything is right, cut the shims. Apply spray foam insulation recommended for windows. Refer to the specific manufacturer instructions.
To fit the sill adapter, measure the height from the window to the sill, then cut the adapter with a sharp utility knife. Drill two weep holes at the bottom and lock it on the window. Install exterior trim around the window frame and seal the edges, but don’t cover the weep holes. You can paint the molding if you want. Then apply caulk along the interior trim.
That’s one window in place – now you’re ready to tackle more.
