Replacing a broken glass pane in a steel-casement window can be a delicate and precise task, but with the right tools and techniques, it’s a project that many homeowners can tackle themselves. The key to success lies in getting the replacement glass sized just right to fit snugly into the window’s frame.
Measuring for the Perfect Fit
The trickiest part of replacing broken glass panes in steel-casement windows is ensuring the replacement glass is the exact size needed to fit the window’s grooves. To get the measurements right, you’ll need to carefully examine the existing frame and take precise measurements of the length and width of the glass pane opening.
When ordering the replacement glass, be sure to request that it be cut 1/8 inch shorter than the exact groove dimensions in both the length and width. This small gap of 1/16 inch on each side between the edges of the pane and the rabbet groove is essential, as it allows the glass to expand and contract with changes in temperature and weather without becoming stuck or cracked.
Gathering the Necessary Tools
In addition to the replacement glass pane, you’ll need a few other tools to complete the job properly:
- Latex glazing putty
- Pliers
- Heat gun
- Flexible putty knife
- 1- or 2-inch stiff steel putty knife
- Flathead screwdriver
It’s also important to wear safety goggles and gloves when working with broken glass to protect your eyes and hands from potential injury.
Removing the Old Glass
The first step in replacing the glass is to carefully remove any remaining shards of the broken pane. Use the pliers to gently pull out all the glass fragments, taking care not to cut yourself.
Next, use the heat gun to warm up the old glazing putty around the edges of the frame. This will soften the putty, making it easier to scrape away with the flexible putty knife. Be patient, as the putty around older windows can be as hard as concrete and may require several applications of heat to fully soften.
Once the putty is removed, use the putty knife or the tip of a screwdriver to pry out the spring clips that are holding the glass in place. These clips will be buried under the old putty, so you’ll need to dig them out carefully. Be sure to save the clips so you can reuse them later.
With the old glass and hardware removed, thoroughly clean and inspect the rabbet groove in the frame to ensure there are no remaining glass shards or bits of putty that could interfere with the new pane.
Installing the Replacement Glass
Now it’s time to prepare the frame for the new glass. Start by applying a 1/16-inch bead of fresh glazing putty along the inside edge of the rabbet groove where the glass will sit. Gently press the replacement pane into the putty, allowing it to spread out and create a moisture-tight seal.
Position the new glass pane, making sure there is a 1/16-inch gap between the edges and the frame on all four sides. Secure the pane in place by pressing the spring clips back into the sash, spacing them evenly around the perimeter.
To finish, form a 1/2-inch-thick rope of putty and press it firmly along all four sides of the glass, overlapping the edges slightly. Use the putty knife held at a 45-degree angle to smooth and shape the putty, removing any excess.
Finally, allow the putty to dry completely, then repaint the repaired area, overlapping the paint slightly onto the glass to help seal the edges.