Repairing Putty Window Glass

How to Replace Single Pane Window Glass from a Window Frame

By Mark J. Donovan

Do you have an old single pane window that needs a window pane repaired or replaced? You might be surprised to know that repairing putty window glass is not so difficult to do, even for the neophyte DIYer.

When it comes to repairing or replacing an old window glass pane all you really need to do is learn how to remove the old pane from the frame and install a new one. The actual cutting of the new window glass pane can be left to the professional glass cutters. Simply take the piece of removed glass, or glass measurements, to your local glass store and have them cut you a replacement piece. You can then easily install the new pane in the frame to have the window looking like new again.

With old single pane windows, glazing putty is used to hold the window pane in the frame. To repair a broken or damaged single window pane your best method is to simply break it out of the frame. Place an old sheet underneath the window and put on some safety glasses and heavy work gloves. Then use a hammer to knock out the glass from the window frame. It’s best to knock out the center of the glass leaving shards around the window frame edge. After knocking out the center of the glass use your gloved hands to pull out the shards of glass still stuck in the frame. As you pull out the shards of glass, flex the glass to loosen up and remove the old dried out window putty.

After removing the glass, use a putty knife to remove the residual window putty and glass. Make sure to scrape the window frame down to the wood. While scraping away the putty you’ll find small pieces of metal, known as push points, imbedded into the putty and the window frame. They are used to hold the window glass in place until the putty has been installed and had time to dry.

Discard the old push points as you’ll use new ones when installing the new window pane. Make sure to pick up some push points at your local hardware store before starting your putty window glass repair.

After removing all the glazing putty and glass shards from the window frame, clean it out thoroughly with a vacuum cleaner or small brush. Then measure the height and width of the window frame. Make sure to measure the height and width, each, at three places to get a very accurate assessment of the window frame opening.

Record these measurements and take them to your glass store where a new window pane can be cut to the measured dimensions. The glass cutter should use the smallest measurement for both the height and the width, minus an additional 1/8th inch, for determining the actual cut sizes.

After returning home with your newly cut piece of glass apply a thin bead of window glazing putty around the window frame where the window pane will sit. Then place the glass pane into the window frame. The thin bead of window putty will help hold the window pane in place while you insert the push points into the window frame. Use a flat blade screw driver to push the push points into the window frame, however be careful not to break the glass in the process.

How to Install a Window Ebook

Finally, put another 1/8th inch thin bead of glazing putty over the window pane and around the window frame. Press it firmly into place and use your putty knife to keep the putty line straight. After the glazing putty has cured, lightly sand the putty and then apply paint to complete the window glass putty repair.

If you need more help on choosing the right window replacement for your home, contact one of our pre-screened window installation contractors. They can help you select the replacement windows that are right for your home and budget, and perform the installation.

For more information on Installing Replacement Windows and Interior Window Trim

  • See the Installing a New Window Ebook from  The Installing a New Window Ebook provides easy to understand, step-by-step instructions, on how to remove an old window and install a new one. Pictures are included for every key step in the process.
  • See the Installing Interior Window Trim Ebook from  The Installing Interior Window Trim Ebook provides easy to understand, step-by-step instructions, on how to install interior window trim around a window. Pictures are included for every key step in the process.

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