How to Install Replacement Windows

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Installing replacement windows is a key consideration whether you are remodeling your home to increase its value, or to be more energy efficient. But the thought of installing replacement windows often deters homeowners. Don’t let it. If you are handy with carpentry skills and have some home remodeling under your belt, you can tackle replacement window installation.

Handy Window Installation Tips

You should assume it will take around four to six hours to replace an average size ground-floor window. First, check to make sure existing window frames are sound and square. If not, you’ll need to make repairs. A sound and square existing frame makes it much easier to use replacement windows.

When you’re researching how to install replacement windows, you want to look for fully-assembled, ready-to-install replacement windows. These will more easily insert into existing frames.

You can also check the websites of window manufacturers for additional tips on how to install replacement windows.

Step 1 - Measure

Measure width, jamb-to-jamb, in three places: across the top, middle and bottom. Record the smallest of the three measurements. Measure the height from the top of the sill to the underside of the head jamb: at left, middle, and right. Note the smallest of the three measurements. Measure the diagonals to check the frame’s squareness. Finally, use an angle tool to determine sill slope.

Step 2 - Remove the Sash

The next step in how to install replacement windows is to remove the sash. Unscrew or pry off the wooden stops to the lower sill. Use caution if you’ll be re-using them as they break easily. Then take out the parting beads (your window may not have them) to remove the upper sash.

Step 3 - Remove Jamb Liners

Old pros at installing replacement windows know you next need to use a pry bar to remove any vinyl or aluminum jamb liners. If you’re working on an original window, take out any remaining wooden stops, being sure to leave both interior and exterior casings intact.

Step 4 - Remove Fiberglass

Remove any existing fiberglass from the weight pockets. For new insulation, polyurethane foam is best. Drill 3/8-inch holes through the frame at each end and in the center. How to install replacement window guides will have more information on this step.

Step 5 - Spray in Foam

After you spray in foam, allow the excess to harden for about 6 hours and then scrape off.

Step 6 - Add Caulk

Apply two continuous beads of caulk.

Step 7 - Install Replacement Window

Use a 2-inch screw to fasten replacement window loosely to the frame. Close and lock the sash to test it.

Step 8 - Add Finishing Touches

Caulk, prime, and paint any gaps. Go over everything to make sure you installed your replacement window correctly before you move on to the installation of the next window.