What Causes Windshields to Crack?

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If your windshield cracked for no reason, you’ll know just how alarming it can really be. You might have a thousand questions running through your mind and thinking that you’ll never get in your car again. It’s easy for us to say but don’t worry- simply read through this article! Below, we’ll discuss the reasons why your windshield cracked, what to do about it and how to stop it from happening, again.

Why Do Windshields Crack?

There’s a wide variety of issues that can cause your windshield to crack- but they all boil down to two main problems, that can turn into a larger spiderweb of real issues. Those two things are the weather and direct damage to your car windshield. To get a better idea of how these can create cracks in your windscreen, read on.

Cracked windshield

The Environment

The environment is the number one contributing factor that leads to your car developing a windshield stress crack. Of which, you’ll need to pay particular attention during the following:

  • Hail

Large hailstones can be a hazard on the road for many reasons. Not only do they cause slips on the road, later compacting to create large icy areas, they can also cause your car to hydroplane (where you have your brakes applied but the car continues to move forward due to the lack of friction on the road) by getting stuck in your tire crevices. Finally, they are also responsible for hitting your car’s windshield at force, causing minute- or sometimes large areas of- damage to the glass.

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This may remain hidden for some time so, naturally, it can be hard to attribute the damage to this, initially. If you’ve had any hail in your area recently, it’s likely that this is the cause.

  • Cold

During the colder months, the temperature can drop rapidly in certain climates. If you’re closer to the equator, this is less likely to happen to you, but it does still happen. Most car windscreens are tempered to accommodate for temperature changes- within reason.

If there’s a sudden change in temperature in your area, the glass of your windscreen may naturally try to contract, causing distortion and therefore cracks your windshield.

  • Heat

Similar to the above, except this can happen over longer periods, too. In this case, the glass will most likely have expanded beyond it’s normal reach, creating a distortion in the windscreen and- inevitably- causing the glass of your car to crack. The windshield is particularly prone to this, as it’s such a large surface area, with less chance for the heat to disperse.

Sometimes, even something as simple as direct sunlight can cause your car to heat up- so, just because it doesn’t seem very hot to you, it doesn’t mean that it won’t be too hot for your car’s windscreen.

  • Pressure changes

As opposed to barometric pressures, this refers to sudden changes in pressure from environmental forces such as strong winds, changes from high to low spends (or vice versa) and even something resting on the windscreen glass. These can all create a crack in the glass, if they’re strong enough.

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Simply put, these are all examples of a windshield stress crack, meaning that the change in the environment has been too much for your car’s windscreen, as they haven’t been able to adapt under the pressure of the changing environment. Therefore, the best way to avoid these damages, is to place your car in a protected or shaded area, ideally a garage- although building a port over your driveway can also help to eliminate some of these risks.

broken windshield

Direct Windshield Damage

Naturally, damage to your windshield can be more obvious than environmental factors, however these can happen so suddenly that they’re very easy to miss.

  • Debris on the road

As much as we’d all love for the roads in our towns and cities to be smooth and fresh, we also know that potholes and damage to the road cause debris to become scattered around. This debris can become a hazard, especially at high speeds and in busy areas, as it’s likely that dirt, stones and broken up tarmac can flick up alongside wheels, hitting your windshield and causing cracks.

  • Structural damage

Unlikely as it may be, sometimes what seems like a windscreen breaking for no reason is actually the result of structural damage that developed during production. The most common area you’ll usually discover these issues is around the outer perimeter of the windshield, where the glass can become more thin- or simply through the adhesive used having an incorrect make-up, or similar, which breaks down the glass, or becomes defective over time.

These defects can be documented by the manufacturers, so if your windshield has cracked recently and you’re not sure why, it might be worth calling up the company involved and seeing if there have been any recalls. In fact, a great place to check is Glass.com, which keeps details on any defective products- and is independent of any production companies, so you can be sure the result is genuine.

  • Direct impact
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This might not be the most unheard-of reason, and it certainly shouldn’t come as a surprise if it happens, but a direct impact is one of the most common reasons for a broken windshield. If you have had a side-on collision, the pressure will cause your windscreen to crack as the pillars crumple. Meanwhile, if the collision is head on, the impact itself will likely shatter your windshield.

This can be frustrating, but unlikely to happen, as long as you follow appropriate road safety, as well as the highway code. Always keep a safe distance from other drivers and continually check for hazards along the road. The good news here, of course, is that the reason is clear and your insurance will take you through the best methods to resolve your issue.


  1. Is It Safe to Drive a Vehicle With a Cracked Windshield? – YourMechanic
  2. How to Replace a Windshield – HowStuffWorks

Originally posted 2023-10-21 05:37:35.

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