New, vinyl replacement windows are low-maintenance, offer energy-efficient features and operate smoothly for years.
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You have two choices with replacement windows: full-frame windows and insert windows.
Full-Frame Replacement Windows
Insert or Pocket Replacement Windows
This project gives you step-by-step instructions for installing an insert or pocket window from the exterior of a house. Some replacement windows can be installed from the interior or exterior. Check the manufacturer's documentation to get specific instructions for your windows.
See Types of Windows: Replacement Window Buying Guide to learn about the different styles of replacement windows that are available.
Determine height and width of the pocket opening. Measure inside the existing frame rather than between the stops that hold the sashes in place (you'll have to open the lower sash to get the measurement). Measure the height at the left, middle and right of the window. Measure the width at the top, middle and bottom. Use the smallest height and width measurements when ordering your windows. Watch How Do I Use a Tape Measure? for tips on taking accurate measurements.
Don't proceed until you have your new windows and have measured them all make sure they'll fit.
Lowe's will calculate the exact replacement window size for your application. Typically, the new window must be 1/2 to 3/4 inches smaller than the opening.
Windows are built differently, so the steps needed to remove yours may vary. Sometimes it best to remove the sashes from the inside, but for the existing windows on this project, it will be easier to work from the outside.
Homes built before 1978 may have lead paint. Contact a professional for help.
If you have a storm window, remove it first. Some storm windows can be removed by lifting them out of their channels. Others might require removing screws that hold the storm window in place.
Score along the edge of the storm window frame with a utility knife, remove the screws and use a pry bar or putty knife to remove the frame. A paint multi-tool (sometimes called a 5-in-1 tool) is also helpful for this step.
If your existing windows are older, they may have either sash weights or sash springs that you need to remove.
Sash springs are under tension and might snap into the window sash track. Be careful of the springs and plastic covers.
Identify any stops on the existing window. An old, wooden window has stops holding the sashes in place: interior stops, parting stops between the two sashes, and exterior stops. If you're installing from the inside, remove the interior stops and leave the exterior stops in place. If you're installing from the outside, as with this project, remove the exterior stops but leave the interior stops in place.
Use a utility knife to score where the stops meet the frame. You might be able to pry them off. If you can't pry the stops off cleanly, they're probably embedded within the frame and need to be cut using an oscillating saw. Let the saw blade do the work and be aware of nail locations. Remove the top sash.
Remove the parting stop and the lower sash.
Fill all holes with wood filler and make sure you have solid wood where you'll screw the new window into the frame. If you find damaged or rotten wood, remove it and cut wood to replace it. Attach new pieces with screws and wood glue.
If your window has weight chambers, fill them insulation before installing the new window.
Clean the opening. Use a shop vacuum if needed to remove all the dust and debris.
Apply flashing tape to the sill. It should fit the length of the sill and extend up the vertical leg of the stool (the bottom ledge of the interior side of the window). Be sure to work it into the corner of the stool.
Check the sill for level and to make sure there's no bowing. If necessary, use shims to make the sill level (illustration to the right). Make sure they are placed correctly for proper leveling and secure them with screws and flashing tape to prevent any movement.
Dry fit the new window into the opening. You should have a small gap around the frame. Set the window aside.
A large window can be heavy. Get help moving it and supporting it during installation.
Place the window in the opening, resting it against the interior stops and pressing it firmly against the caulk. Use shims to secure the window, placing them at the pre-drilled frame screw holes.
From the inside, drive screws into the holes and through the shims.
Check that the sashes sit evenly in the frame. If needed, use additional shims at the meeting rails (the horizontal frame elements on the sashes that meet when the window is closed) to adjust the frame of the new window.
Check for plumb, level and square and ensure the window operates properly. You can make any additional adjustments with shims. When everything is right, cut the shims.
To check for square, measure the diagonals of the new window frame, not the interior trim.
From the outside, apply spray foam insulation recommended for windows into the gaps around the window. Don't overfill the gaps. Refer to the manufacturer instructions and see Do-It-Yourself Foam Insulation for tips. You can fill larger gaps with backer rod weatherstripping. Avoid batt insulation, which can absorb water.
Measure the height from the bottom of the window to the sill to size the sill adapter.
Use a sharp utility knife to cut the sill adapter to the appropriate width.
Drill two weep holes at the bottom of the adapter and lock it onto the window.
Use a piece of scrap wood to protect the sill adapter when you tap it in place with a hammer.
Install exterior trim around the window frame with finish nails. Use a nail set to finish driving the nails to prevent denting the trim. Seal the edges of the trim with latex caulk. Don't cover the weep holes. Fill any noticeable nail holes with wood putty and paint the trim as needed.
Apply latex caulk along the interior trim to complete the installation.