What Causes Window Glass To Develop Stress Cracks And How Do You Fix Them?

If your window glass is cracking for no apparent reason, it's most likely due to stress cracks. While most window cracks are due to impacts and have an obvious cause, stress cracks will develop on their own. They're typically caused by differences in temperature across the windowpane, and you're most likely to see them form during the fall or early spring. To learn more about why stress cracks form in window glass and what you can do to fix them, read on.

What Causes Stress Cracks?

Stress cracks are most commonly caused by large changes in temperature, which is why they're most likely to occur when nighttime temperatures are cold and daytime temperatures are hot. When the sun rises, the portion of the window glass that's exposed to sunlight will rapidly warm up during the day. However, the portion of glass that's hidden in the window frame will remain cool because it's shielded from the sun.

Glass expands as it heats up, and the expanding glass that's heated by sunlight places a significant amount of tension on the cool portion hidden by the window frame. This tension will cause the window glass to crack. Rarely, stress cracks can be caused by a settling foundation. If one side of the window frame begins to sag due to the house's foundation shifting, then it can place tension on the window glass and cause stress cracks to form.

Can You Prevent Stress Cracks?

Stress cracks are very difficult to prevent since they're mostly caused by changes in the weather outside. You can reduce the risk of stress cracks appearing in your window glass by switching to a thicker windowpane. Thicker glass has more thermal mass, which means that it will heat up slower during the daytime. This reduces the risk of stress cracks occurring.

Additionally, you can also switch to using tempered glass in your windows. Tempered glass is stronger than the annealed glass that's commonly used in windows, so stress cracks are less likely to form.

What Should You Do to Fix a Stress Crack?

One inexpensive way to fix a stress crack is to fill it in with epoxy. Hardware stores carry glass repair kits that provide you with all the tools you need in order to fill small cracks in your window glass. Filling the crack with epoxy slows down its spread and makes the cracked window glass less likely to break entirely.

Unfortunately, using epoxy isn't a solution. The epoxy filler is highly visible, so it will negatively affect the appearance of your window glass. In addition, it won't fully restore the strength of the glass—it's still more likely to shatter or develop additional stress cracks compared to a windowpane that's completely undamaged.

The best solution is to call a window glass repair service and have them replace the cracked windowpane. Removing the cracked windowpane and replacing it with a new one is a quick and inexpensive process. If you are able to remove the window sash with the cracked pane, you can even take it to the window glass repair service yourself instead of having them come to your home, which gives you even greater savings. Replacing the cracked window glass will restore the strength of your window, making it less likely to break during severe weather or due to impacts.

Look for a company like Nor Sac Glass Company near you that provides window glass repair services.