3 Causes Of Windshield Stress Cracks

A windshield crack may occur when the glass is struck by an object. Often, the flaw begins as a chip but spreads if the chip is not filled promptly with resin glue. Another type of flaw is known as a stress crack. These can develop for a few reasons. Technicians providing auto glass services can replace windshields through mobile services or at their repair shop.

Impact and Stress Cracks

Impact cracks start wherever the glass was hit. In contrast, stress cracks usually begin at an edge. They also tend to quickly extend across the surface, making repair work impossible.


Manufacturer and Installation Issues

The windshield may have been inherently defective all along. One possibility is a disruption of the annealing process, which is how manufacturers strengthen the glass. In this case, the crack develops from an edge where there are weak spots. Unfortunately, service technicians generally cannot confirm this was the cause. That means the windshield or automobile manufacturer cannot be held responsible. 

Another possibility is improper installation. There could be weaker adhesive pressure on one side. This typically only occurs when someone replaces a windshield as a do-it-yourself project. Auto glass technicians have completed training and have the skills to do the work without error.

Extreme Temperatures

Stress cracks can result from abrupt temperature changes. This is not one of the more frequently seen causes because temperature changes usually are gradual. Temperature-related cracks can occur if the air conditioning has been turned on high after the vehicle has been parked in very hot sunshine. Cold air blasting through the top vents on the dashboard can crack the hot glass.

Blowing air from the defroster onto an ice-covered windshield is unlikely to cause problems because the air warms up slowly. But if somebody tries to melt the ice with something like a hairdryer, that could even break the glass.


Cracks from pressure are categorized as stress-related because nothing actually struck the glass. However, something heavy enough to break the windshield was there. For example, it may be that a person decided to sit against the windshield. A vehicle roof is strong enough to hold a fully grown person or two, but windshields are not designed to support that much weight.

Driving with a cracked windshield is unsafe. The flaws tend to spread and begin interfering with visibility. When stress or impact cracks occur, auto glass technicians can replace the windshield with mobile service or at the repair shop. Contact an auto glass service for more information.