Window Pane: How to Replace with New One?

Glass is fragile, as we all would know all too well, and therefore it’s almost a certainty that some of the window panes in your home would break at some point. If you have kids, sooner or later a baseball is going to come flying through a window, instead of safely into a catcher’s glove. Or you might have an accident indoors while decorating a Christmas tree, ending in a branch poking a hole through a closed window.

Window Panes

Accidents happen, unfortunately, and when they do, you need a contingency plan. Chances are that you haven’t saved up any loose change in a jar to prepare for unexpected window breakages. That means that, if you have modern double glazed windows, you are in for an expensive replacement exercise. But older, simpler, single glazed windows are much easier to work with, so you may want to try your hand at replacing your broken windows yourself. How hard can it be, right? Well, not that hard at all, thankfully. But to help you remove some of the trial and error from your first attempt at replacing broken windows, here’s a neat little step by step guide to help you through the process.

Things you will need to get the job done

Before you can get started, you need to head to your tool shed or garage to gather all the tools and materials you will need. You may also need to take a trip to the hardware store to purchase everything you don’t have.


  • Safety first! Heavy duty gloves to handle glass, safety goggles to protect your eyes.
  • Putty knife
  • Heat gun
  • Sandpaper
  • Tape measure
  • Paint brush
  • Caulk gun 


  • Replacement glass
  • Glazing points
  • Glazing compound or putty
  • Paint primer
  • Linseed oil or wood sealer
Replacing Window Pane

What to do, step by step

1. Remove window frame (optional):

To make the work easier, it is advisable to remove the window sash if possible. This will enable you to lay the window down flat at a convenient height.

2. Remove broken glass:

Remove the broken glass carefully, using gloves to help prevent the glass from cutting your hands. You should also use safety goggles in case you stab yourself in the eye with a sharp shard of glass. Also, remove the old glazing points from the frame.

3. Scrape off old glazing putty:

Use your putty knife to remove all the old glazing putty. Use a heat gun to soften the putty, if it’s the good old-fashioned kind. Be very careful not to burn the frame. If it’s a newer window, it may have a vinyl glazing strip that you can pull out easily.

4. Sand grooves:

Next, you need to sand the grooves of the frame to remove old putty and paint residue. Then you need to paint the surface with wood sealer, or with linseed oil, if you will be using traditional glazing putty. This will help to keep the wood from drying out the putty too quickly as it absorbs its oil.

5. Measure size of new glass:

Using your tape measure, measure the inner dimensions of the window frame. Then subtract about 1/8 inch from both the length and the width, otherwise, you may find that you have a fit that’s too tight. You can always trim it to size with a glass cutter, but it’s better to have it cut to the correct size by the company that supplies the glass, in case your glass cutting technique needs some practice.

Installing Window Panes

6. Install new glass:

Now that you’ve prepared everything, the real fun can begin. Before you grab the new pane of glass, you first need to prepare a layer of glazing. Take the caulk gun and insert a tube of glazing compound. Then apply a thin layer of glazing compound to the grooves in the frame. If you are using old-school putty, you need to kneed it until it’s soft and add linseed oil to get it to the consistency recommended by the manufacturer. Then you need to roll it into thin strips and smooth the strips down into an even layer on the inside of the frame.

Now you can carefully insert the new pane of glass onto the layer of putty or glazing compound, and bed it down gently. Then, finally, you need to insert glazing points into the frame. Lay them flat on the glass, and carefully wedge them into the frame using the putty knife. Space the glazing points about six inches apart.

7. Apply glazing compound:

Now that you have set the glass in place, the final step is to apply a layer of putty or glazing compound to the outside of the frame to cover the glazing points, and to create a neat finish. If you are using a caulking gun, squeeze the trigger with even pressure, while applying glazing compound to the edge where the glass and the frame meets. Then, take a wet cloth and smooth the glazing down. If you are using traditional putty, roll it into a sausage as long as each side of the glass, and smooth it down while holding the putty knife at an angle.

8. Paint the frame:

The last step is to paint the frame. You can’t do this right away, however. Depending on the kind of putty or glazing compound you used, you will need to wait anything from a few days to a week before you can paint over it. Traditional putty will take the longest, but sometimes it can be painted over as soon as it has formed a skin over the putty. It is best to wait until it has hardened, and then paint it with an oil-based primer. More modern glazing products, such as latex glazing, may be ready to paint over within a day.

When painting the window frame, paint about 1/16 inch over the edge of the glazing, onto the glass. This will help to ensure that water can’t get behind the glazing. When the primer has dried, you can finish the job by painting over the primer with a suitable weatherproof exterior paint.

About the Author: This article is a contribution made by Apex Window Werks, a house window repair & replacement company located in Chicago, IL. The company deals with wood windows more than 8 years already. Feel free to get in touch with them for a free estimation.

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