How to Replace a Window: A 10 Step Guide

woman measuring a window

Did you know that 25-30% of your heating and cooling is lost through your home's windows?

Installing replacement windows not only saves you money on your energy bill, but it also adds value to your home. Read on to learn how to replace a window in 10 simple steps. 

1. Measure Your Window Opening

Measuring your window correctly is one of the most important things when replacing windows.

The easiest way to measure the width and height is to remove the trim first. Don't forget to measure the depth. Otherwise, you could have a window frame that doesn't sit flush with your wall. Trying to make it work by sanding the frame or making the jamb thicker is a lot of work.

It's wise to measure correctly once and for all. Installing replacement windows can be tricky. If you aren't handy, leave this project to the best window replacement company around.

2. Remove Stop, Sash and Parting Stop

Once you have your measurements, it's time to remove the interior stop, sash, and parting stop.

Use a stiff putty knife to avoid damaging your window frame. Use the putty knife to score the joint between the window frame and stop before you pry off the stop.

The parting stop might be difficult to remove due to hardened paint. You can use pliers to break off the lower half. You can also gently use a chisel.

Pull the nails out with pliers.  

3. Do a Trial Install First

The most important thing to remember when learning how to install replacement windows is to do a trial install first.

Rest the bottom of your new window on the sill and tilt it into position against the blind stop.

Don't nail and caulk your window on the first try. While it's in its trial position, notice how the shims fit. Then use a pencil to make marks on the wall so you'll know where they go.

Then, loosely fasten the window into the frame with screws in the lower let and upper right corners. But don't install the screws all the way in.

At this point, you can readjust the screws or window in the opening to get it just right. 

4. Caulk the Sill&Put in Your Window

Now it's time to caulk the sill. Use a 3/8" bead of sealant first. Then put the new window in your opening. Use a square to check each of the four corners.

5. Tap in the Shims

Install your shims where you've marked the locations. At this point, don't knock the shims all the way in. Leave around one inch sticking out in case you need to remove the shims.

6. Install Mounting Screws

Now you can screw in the mounting screws in both the top and bottoms of each side jamb. Make sure to not over-tighten.

Then, move the header up until there is no longer a gap between the window and frame. Next, fit the header in position.

7. Test the Window

Now that the screws are in place, you can test the sashes. You want to feel a nice easy glide.

If the sashes feel tight, you can use adjustment screws to adjust the sashes. If this doesn't work, you might need to remove the shims and try thinner pieces.

8. Saw off the Shims

Once your shims are working as in place, saw off the edges that are sticking out. Use a miter saw to do this.

9. Caulk

Caulk the inside of your window. Apply caulk to all the joints in the window frame as well as the joint between the frame and the wall.

10. Install Inside Stops 

Use little finishing screws to install the inside stops. And that's it! You have a brand new replacement window.

Final Thoughts on How to Replace a Window

We hope these 10 steps on how to replace a window help you get a good sense of how to replace house windows.

Come back soon for more great home improvement articles. 


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