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Why is My Window Glass Cracked?

10/17/2014 11:50:00 AM

So you’ve noticed that one or more of the windows in your home has a long crack running across it, but the cause of the damage isn’t apparent. So what happened and what should you do?      

Understanding Stress Cracks in Windows

Cracks can occur even when a window is not struck. The most common cause of inexplicable cracks in windows is stress. Stress cracks—also referred to as thermal stress cracks—can occur in windows when a thermal gradient causes the glass in your window to expand by different amounts in different parts of the window. Eventually, depending on the range of temperatures and expansion, the glass may become compromised by the stress of expansion and a crack will form.

You may have experienced stress cracks in the kitchen before if you’ve ever exposed a hot dish to cold water. The stress created from the rapid expansion and contraction of the baking dish can cause the dish to crack or break completely.

The same thing can happen to your windows.

If your windows are cracked and need replacement find your local Weather Shield dealer for new, beautiful, and secure windows:


What Causes Stress Cracks to Form?

Stress cracks are most common in windows that are partially exposed to shade—particularly on large windows. If your windows are located beneath overhangs or partially shaded by trees or other structures, your risk of stress cracks increases because this can cause dramatic changes in temperature on the glass between the shaded and unshaded regions.

Sometimes, stress cracks can occur simply because of the weather outside. If you experience extreme temperature changes overnight followed by quick warming in the morning, stress cracks are more likely to occur.

How to Know if You’ve Experienced A Stress Crack

Stress cracks in your windows are relatively easy to identify. They will almost always start perpendicular to the edge of the glass. The crack will generally start at the glass edge and extend 1 – 3 inches from the glass edge—growing larger over time as the glass has become compromised.

Preventing Stress Cracks in Your Windows

Unfortunately, you cannot fully eliminate the risk for stress cracks in your window glass, as they are a natural consequence of glass expanding and contracting during temperature changes. If you are replacing your windows, consider installing a thicker glass and choosing glass features that are ideal for your climate. While this will not provide 100 percent protection from stress cracks, it will decrease the risk of them occurring.

Window Repair

If you have Weather Shield windows and have found a stress crack in your windows, please contact a local Weather Shield dealer in your area or contact us directly for assistance with the replacement of the glass or window.

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