A Car Owner's Guide To Windshield Stress Cracks

Posted on: 24 March 2022

Not all windshield cracks begin with a rock strike or similar impact. Stress cracks are another type of crack that can affect your car's front windshield. 


Unlike chips and impact cracks, a stress crack doesn't have any type of obvious strike point. Instead of spider webbing out from a central point, such as when the windshield is struck by a rock, the crack follows a roughly straight or curved light with few sharp angles or branches. Stress cracks often, but not always, begin near the edge of the windshield.

One way to verify that a crack is a stress crack is to place the nib of a ballpoint pen in the crack and lightly trace its course. If the pen doesn't dip down, then that means there was no impact to cause the crack to begin so it must be a stress crack. 


The most likely cause of a stress crack is temperature fluctuations. These cracks often form in winter due to poor ice removal habits. Using hot water to melt an icy windshield, for example, can shock the cold glass and lead to a crack. Similar can occur if you use full heat defrost on an ice-cold window. Less common but possible is for a crack to form in summer if you blast the air conditioner when the windshield has been exposed to hot, direct sunlight.

Weight on the windshield can also lead to stress cracks. This is frequently seen after major winter storms drop a lot of heavy ice and snow on top of a vehicle. If the excess weight isn't removed, the stress of it can lead to window cracks forming.

Repair Options

Two things determine whether a stress crack can be repaired -- size and location. Generally, a crack must be less than 3 to 6 inches long and no longer actively growing in order to respond well to a repair.

Stress cracks that begin right at the edge of the windshield aren't good candidates for repair as the crack may have penetrated beneath the windshield's edge seal. A crack also can't be repaired if it is right in the driver's line of sight, as even a repaired crack compromised visibility somewhat. If the crack is too long or in the wrong location, then a windshield replacement is necessary.

Contact a windshield repair and replacement service if you suspect a stress crack is forming on your car's windshield.