Fixing a Broken Window Pane

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Mar 24, 2011 | Kevin Stevens

lizevans/stock.xchngWindows these days can be pretty high tech. It is not uncommon to see double and even triple paned window filled with Argon and coated with special materials to limit heat gain and loss. The days of a simple sheet of glass set in a wooden frame with glazing points and putty are rapidly fading into history. If you have a broken window pane, the fix can vary from “simple” to “I’d better call in the pros.”

Traditional Single Pane Windows

A few months ago I got to repair a broken window pane for a client. This was an old architectural gem currently being used as an interior window to let light into the guestroom from the main living room area. Easily 50 years old, it was of the traditional single pane, points and putty configuration. Repairing such a window is pretty straightforward and involves these basic steps:

  • The first step, if possible, is to remove the window from its installed location. It's easiest to work on a window that is not installed. Many older style windows can be removed by popping off a few narrow strips of molding or trim that hold the window sash in place.
  • With the sash removed, the next step is to take out the old putty and broken glass. This should be done wearing sturdy leather gloves and safety glasses. Something more than good intentions must separate broken glass and its sharp edges from delicate skin. Chances are the putty is dry and brittle, so a stiff thick putty knife is helpful in removing it.
  • Buried in the putty you will find a number of glazing points, designed to hold the glass in the window frame. These can be simple triangles of metal or the spike type with a “L” shaped shoulder. A set of needle nosed pliers, or a thin screwdriver, can be used to pull these out. 
  • Once the points are removed, the rest of the glass may be lifted out. If this broken window pane is somewhat intact, it can be used as a template for its replacement. Basic squares and rectangle are pretty easy to measure; arcs, curves and circles are more complex, and here a template can save lots of time and energy.
  • Now that the glass is out, you will need to remove the thinner layer of putty that was below the pane. This layer usually comes away at lot easier than the top layer you worked through to get to the points.
  • With the pane and all remains of glazing putty removed, now is the time to correct any minor damage to the window frame. Excessive gouges in the wood, cracks, etc. should be fixed. A bit of glue or wood filler often makes quick work of this. A little touch up paint or varnish can be applied to these bare surfaces to ensure their longevity.
  • To install the new pane, a thin “bedding” bead of glazing compound is applied to the window frame and the glass is set in place.
  • With the glass pressed into place, install new glazing points in order to keep the pane seated in its spot.
  • Set a finishing layer of glazing compound above the points and bevel with your putty knife for a smooth transition from the window frame to the pane. This is often the tricky part, as getting a nice looking surface takes practice. Don’t worry too much -- glazing putty is slow to dry so you can keep working it until you get a smooth finish.
  • Once the putty is in, the window sash can then be re-installed. After a drying period the glazing compound should be sealed or painted to protect it from the elements if so exposed. This drying time will vary based on your climate and temperature and can run into weeks. Keep checking to see when it is ready.

Double Pane “Modern” Windows

The above steps work great for the older single pane style windows. But these are becoming pretty rare in homes. Chances are your windows are more modern, energy efficient and a bit harder to repair. I've fixed some windows set in wood or metal frames that allowed disassembly and reassembly. Here a pane is often set with a gasket in lieu of the older putty. Screws or moldings allow the pane to be removed and reinstalled. If your window falls into this category, replacing the pane is still a viable DIY project. Depending on how the sash or panel is configured, this can sometime be a bit easier than the old putty installs.

Sash Replacements

Many windows today are built from “welded” vinyl and therefore are beyond the reach of most DIY homeowners’ skill sets. In these cases, it is normally required to replace the entire sash or in extreme circumstances the whole window. These windows are often on the lower price scale, and easy replacement is one of the sacrifices made for this cost advantage. 

Some window replacements do not involve a broken window pane, but merely bad or broken seals. In the 20 years I have been in my home, I've replaced a few of the large panels in my sliding doors. To do so, I removed the slider or fixed panel and took it to my local glass company. They quickly prepared a replacement, which I then installed. This “partial” DIY repair saved me the cost of a service call … which in many jobs can be 50% or more of the price. Parts and labor for one of my sliders was less than $150. However, transporting a 30” x 80” window is not a possibility for many homeowners that's when it's best to call in the pros to complete the whole job.

Updated October 4, 2018.

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