Why Do Windshields Crack?

Ever had your windshield break for no apparent reason?

Well, glass doesn’t really break “for no reason.” There could be several causes for your windshield cracking, breaking or shattering. Let’s take a look at some of the more common ones.

There are, of course, several obvious reasons for a chip or crack in your glass – flying grave or other road debris dropped from the vehicle in front of you on the highway. In those cases, the common sense rule of not following too closely, staying alert and avoiding rides behind open-top trucks can prevent many of these glass mishaps.

But what about the not-so-obvious causes? If you notice your windshield has been chipped, cracked or otherwise broken, consider these possible causes. But more important than the cause is the correction. Take steps to have the glass repaired or replaced as soon as possible.

Possible Causes of Broken Windshields

Poor Installation

Factory-installed windshields usually meet a high standard of safety and construction, but sometimes a windshield isn’t installed as precisely as it should. If the glass is installed improperly, the windshield could be loose – causing vibration – or stressed, which can cause cracks.

Temperature Changes

Severe temperature swings can cause glass to expand and shrink rapidly, especially when you use a defroster or even a car heater. Also, the glass typically heats faster around the edges, so the expansion and contraction is happening at different rates, which can lead to cracks.


Like temperatures, sunlight can cause the same problems. The sun’s heat on metal and other materials around the glass can cause the glass edges to expand faster than the middle of the glass and cause cracks. One way to avoid this is to keep your car in a garage or in the shade, if possible.

Pressure Changes

We’re not talking barometric pressure, but sudden pressure changes from shifting from low to high spends (or vice versa), wind gusts, or even heavy objects resting on the glass, can cause stress cracks.


We’ve all seen the weather reports of hail storms, with hailstones described as “golf ball-sized” or “baseball-sized.” Hail is nothing more than a ball of ice traveling at high speed when it hits your windshield – and has the same effect striking your glass.

Glass Imperfections

In a few very, very limited cases, the glass installed in your vehicle may have been defective. You may not be able to make this determination, but an auto glass shop may be able to. Quality glass shops are also aware of recall notices for defects involving glass or related items. In fact, Glass.com often notifies its affiliate shops of any such recalls.

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How Serious is a Cracked Windshield?


The Good and the Bad

So the bad news is that you have an unsightly crack in your windshield. The even worse news is that you need to take time out of your day to do something about it. The good news? Having the damage fixed by a trained technician can be a quick and painless process, and for some, it’s already covered by insurance. Plus, Glass.com makes it easy by providing instant price quotes from shops in your area and you can book conveniently online in a matter of minutes.

So how do you know if the damage needs to be fixed? The short answer is it almost always needs to be fixed.

Assessing the Damage

Damage comes in all shapes and sizes, and every crack should be examined by a trained technician. There are two important factors that will determine if you need a repair or if you need a replacement: the size of the crack and its location. Upon examining these two things, a reputable technician will advise you on the next step to take.

But one thing’s for sure, a damaged windshield is usually more serious than it appears and will more than likely require a repair, if not a replacement.

The Underlying Danger

Your crack may be small now and easy to ignore, but don’t put off having it fixed. One of the most common problems with cracks, if they are put to the side, is that they have the tendency to grow. And temperature is one of the main culprits for this. Fluctuating temperatures can cause the glass to expand and contract which can worsen the problem.

A crack in your windshield already has likely weakened its structural integrity, which can leave you and your passengers vulnerable in the event of an accident, so why wait for the problem to worsen?

Don’t Hesitate

A damaged windshield can be a serious problem and can put you at risk to injury or harm. So don’t wait to have a technician repair or replace your windshield. If you’re not sure where to find a reputable technician, Glass.com offers instant price quotes from shops in your area.

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2 responses to “Why Do Windshields Crack?”

  1. Hi I just want to ask about my windscreen,this morning I went to work my screen was fine,I park under cover parking Got to my car at 5 pm.And their was a crack in my windscreen it is on the drivers side and runs up from the bottom about 15cm long.Their was no chip their,could the weather coused it.

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