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Why Do Windshields Crack?

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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? You may feel as though your windshield cracked out of nowhere. 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 Front Windshield Cracks

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, 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, 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, offers instant price quotes from shops in your area.

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Phillip Thompson

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16 Responses

  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.

    1. Hi Wilma,

      Yes, it is possible that if you do not see a point of impact that the crack could be weather-related.

  2. I find it interesting that you mentioned that wind gusts can cause stress cracks on a windshield. When you said that, I thought that I should find nearby replacement services for my brother before he leaves on a food trip by car. Doing this will help him get it repaired in case it breaks while he drives over highways at night.

  3. One day I parked my car (TATA NANO) outside , on that evening there was a rainfall, on the next morning the cars rear windshield has seen broken. What might be happened?

    1. Hi Sameer,

      Was there any hail or wind also? Wind could have caused a branch to fall on the car or a large ball of hail could have broken the glass. Or it simply could have been a coincidence that it was raining that night. Unfortunately there are many, many possibilities and without more information it is hard to say what caused the breakage.

  4. My windshield cracked and i have no clue why or how. I see a point of impact but nothing has hit it. Ive had it for a week. Its cracked on the driver side at the bottom. Then today again from the point of impact to the passenger side.

  5. Hi,
    My wife, who doesn’t weigh more than 105 lbs, was waiting for in the car while I went to grab something. The seat as reclined and she had her feet up against the windshield, the windshield cracked! This is a 2018 BMW X5, it seems that there must a manufacturing defect and of course the dealership is denying this. Does this seem normal? Doesn’t seem fair to dish out the $1,000. A windshield should be able to withstand such minimal pressure.

    1. Hi Chris,
      There are many factors that play a role in this. It could be that the windshield already had minor damage that wasn’t readily observable to the naked eye and the pressure cause the damage to spread. Temperature changes also play a part. It does seem a bit out of the ordinary, but difficult to say whether it is “defective”. There are not currently any open windshield recalls for the 2018 BMW X5, but you can file a complaint with the National Highway Traffic Safety Administration if you feel it is warranted.

  6. if you pull on the mirror and twist it really hard the wrong direction of the design, will that crack the windshield?

    1. Hi Greg, it is highly unlikely but if there were other stresses coming into play, such as an existing chip or crack, or temperature changes it might be possible.

  7. Hello sir, is it necessary to leave a little bit of glass doors open to avoid breakage of windshield ( to avoid temperature fluctuations inside the car) when kept outside for about a week or is there no relation to keeping gaps or closing it to the hilt in the glass of the doors? Pl explain as my windshield got cracked without any point of impact. Thank you.

    1. Hi Jimmy,
      Under normal circumstances, no, it is not necessary to vent a vehicle that is parked for a week. Many factors play into windshield breakage and sometimes it is unclear exactly what causes breakage. For example, there may have been pre-existing damage too small to see, and temperature fluctuations caused that damage to expand into a larger, more noticeable crack.

  8. Dear Sir/Madam.

    I am very worried about my car rear windshield found broken. I checked my car physically at 7:05PM found okay but when I was checked at 9:30PM, the rear windshield found broken from Centre and after touching the back door the windshield totally falls down in small pieces.
    I am too much worried about this incident.
    Kindly inform me, what is the main reason for this breakage also I asked from my neighbors about this possible any one body hit solid things to collide the windshield but no any positive response received.
    I am too much worried about this incident without any collision how Windshield damages it self?
    Please share your experience.

    1. Hi Arsalan,
      Thanks for the question. There are lots of causes of glass breakage– too many for us to cover in a single post! Rear windshields are typically made of tempered glass. Tempered glass usually “explodes” when it breaks, fracturing into thousands of tiny pieces. Tempered glass might receive slight damage from a rock or something similar that doesn’t cause immediate breakage, but the damage can still cause breakage later on. Some people refer to this as “spontaneous” breakage because it seems to happen without reason. There is always a reason that breakage occurs, but it might not be easily traceable.

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