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Why Do Windshields Crack and What Should I Do if it Happens to Me?

July 14, 2011

Many of us have had the unpleasant experience of innocently driving along when an errant piece of gravel or other mysterious road debris suddenly puts a dent in our vehicle's windshield. And many of us have had the even more unpleasant surprise of the little nick becoming a five-inch jagged crack a mere few hours or days later.

Windshield replacement is one of the top insurance claims in the U.S. Surprisingly, it doesn't take much to damage a windshield. All it takes is a rock impact the size of the dot a pencil tip makes on a piece of paper to cause serious damage. So, why do this happen and what can we do about it?

Untitled design (4)

Types of Cracks

Edge crack
The most common type of crack, the edge crack is the cause of 60 to 80 percent of windshield replacements. Because of how they are manufactured and installed, the outer 2 to 3 inches of a windshield (the "Crack Zone") have stress defects, which cause this area to fracture much more easily than the rest of the windshield. Even tiny cracks can become 8- to 10-inch long cracks.

Stone break
A small chip that occurs when a stone or other hard debris hits the windshield. This can develop into a large crack over time.

Bull's eye/Half moon
Circular ding, with a cone in the outer layer of glass. A half moon crack is similar, but not completely circular.

Chip
Damage by a rock that causes a small piece of glass to break off the windshield.

Floater crack
Less common than an edge crack is the floater crack, which is caused by severe temperature changes (especially cold temperatures) to stone breaks.

Stress crack
A crack that occurs without anything actually hitting the windshield. The most common causes are a large variation in temperature, like if your car has been sitting in the hot sun all day and then you blast the AC.

If you're interested in getting a quote for a windshield repair or replacement, call our friends at Safelite. They offer mobile repairs too. 877-303-3376 

Does outside temperature matter?

In a word, yes. Without going too much into an explanation of the thermal coefficient of expansion, suffice it to say that a wide range of temperatures has a very direct effect on a chipped windshield. The metal in the frame of your car or truck can expand and contract at a different rate than the windshield glass. This places stress on the windshield frame, which cracks the glass further.

Should I be worried about a crack in the windshield?

Absolutely. Windshields are critical safety devices that help prevent injury and death. They not only prevent ejection during a crash, but also serve as the backboard for airbags by controlling 20 percent of the "crash pulse," which tells the airbag when to deploy during an accident. Windshields also support the roof of the vehicle, which is essential during rollover accidents.

Can you stop a crack once it starts?

Once a windshield is cracked, the stress placed on the ends of the crack almost guarantees that the crack will continue to spread along the same line, much like faults that produce earthquakes. The only exception to this is a conchoidal (dish-shaped) fracture that has no obvious outward rays. Cracks like this rarely spread. But for chips with little cracks radiating out from the center, expect it to spread out.

How much does it cost to replace a windshield? Should I do it?

According to some experts, no replacement windshield is as good as the original. Not only are many replacements done incorrectly, but the initial windshield has to pass so many government tests, that original factory installation cannot be duplicated in the aftermarket. Your best bet is to prevent replacement if possible. You can achieve this by using crack prevention products.

Many insurance companies will repair cracks for free in place of replacing the entire windshield. For cracks that are smaller than 6 inches, repair is recommended. But there are companies that offer products to repair cracks up to 24 inches long.

Chips in the windshield generally cost around $50 to fix. Cracks can cost anywhere from $100 to $200 to repair. Replacing a windshield costs hundreds of dollars and rises to over $1000 if an OEM windshield is used.

How can you prevent cracks?

If you can, park your car in a garage or other temperature-controlled environment. Leaving your car out in the sun or in the cold tends to make the edges of the glass more brittle.

If you notice a crack or ding in your windshield, have it looked at immediately! The longer you wait, the more damage you are in for.


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About the Author

Natalie Josef is an automotive expert at RepairPal, the leading online source of auto repair resources and estimates. With many ASE Master certified mechanics on staff who have decades of experience, RepairPal knows all the fine points of car repair.

15 User Comments

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By , July 09, 2013
My car rental (2013 ford Explorer)developed an edge crack on the upper left side windshield (driver side)while driving south on I-26. The following day, went to the airport and exchange the Ford Explorer for a Ford Taurus and the same thing happened, an edge crack (on the driver side coming from below left wiper area)after driving about 150 miles south on I-95. My question is: Who pays for repairs? My insurance company says I may have to pay the deductible depending on what the car rental agreement wants to do... I don't want to pay for edge cracks that has to to with poor car windshield designs! Anyway, I filed reports with the departments of National HWY Traffic Administration, Federal Trade Commission, Ford Company, car rental company, My insurance company, and my Bank Card company for any dispute situation. I live in Florida. Thanks.
By , January 02, 2014
I had the same problem with a 2013 Ford Taurus rental. I was stopped in traffic on an elevated one way exit ramp. I heard a "pop" sound and then saw a crack in the windshield. Nothing hit the car as traffic was not moving. I took the car back to the rental agency. The crack came from below the black moulding on the driver side of the vehicle. The guys at the rental agency even told me there was no impact as they ran a pen through the crack. The next day I get a call from the rental agency and they tell me that I am responsible for the windshield. I am going to tell them to jump into a lake as I will not be responsible for windshield defects.
By , February 07, 2014
My windshield on my 2014 ford Taurus also cracked. It was sitting under my carport and I went to get in it and noticed a crack, so I called the dealership and told them. They determined that it was a "stress crack" and replaced my windshield (they didn't replace my brow tint though) Today my windshield was fixed and I went to go get my brow re-tented, after we got it done we were on the way home and here a popping sound (almost like popping bubble gum) I looked and there was another crack, in EXACTLY the same place the first one was in. How is that possible? Needless to say I am not happy about this and I think that it is ridiculous. Ford defiantly got a phone call from this afternoon and they will be doing MORE investigation on it... I am not happy!
By , March 21, 2014
my 2013 ford escape also got a crack on the left side. Park it that night and by morning there was a crack.Took it to ford dealership today,they took pictures then determine it was not under warranty.It has to be the design of the windshield that is making all these windshield crack. Keeping all my paperwork since I have to pay for a new windshield,because I believe ford will have a RECALL SOME DAY SOON,because it is happen to often.
By , April 10, 2014
RECALL necessary! 2014 Fusion... windshield was fine yesterday, got up this morning and crack goes from very bottom(under wipers) to very top. No signs of it being hit with anything. $500 to replace it!
By , February 16, 2015
I have a 2011 Nissan rogue. last week for no reason found out ,there is a crack on the windshield (4"), and it was a straight line. After two days the crack line going to the left for (1"). By the way, I do not park my car in our garage and this caused the problem, because of the cold temperature. We live in Edmond, Oklahoma.
By , March 10, 2015
My 2014 ford edge has a crack in the windshield I see that a lot of fords have this problem
By , March 17, 2015
I noticed a crack in my windshield last month. I am in the greater Boston area and it has been an awful winter (in case you hadn't heard). Anyway, got it replaced and the cost was fully covered by my auto policy. Got in the car today and started driving to work, and noticed a very long crack in the new windshield coming from beneath the passenger wiper and spreading all the way across to my steering wheel! Hoping it is determined to be a stress crack, which is covered under warranty by the glass company. If not, I am really disturbed by this re-ocurrence. Hoping it is due to the frigid weather, and I am thinking of getting one of those padded windshield covers. FYI - I drive a 2010 Subaru Legacy.
By , March 20, 2015
Just got an edge crack on my 2015 Escalade. Started at top, parallel to mirror mount.
By , April 13, 2015
I have a 2014 C MAX Wednesday afternoon when I went out to the car there was a crack in it, it now grew to be almost halfway across the windshield in less then a week. I got to the dealer for an appointment they told me because it was at seventeen thousand miles it was no longer under warranty. I bought a premium insurance package when I bought the car to cover anything that is not under the powertrain warranty but when I called the Ford place about it they told me that windshield is not a safety issue it is not considered to be under their premium care coverage I have no ideal why I spent over $2000 for, when its not going to cover a windshield but it will cover a little piece of plastic to go over the bolts in the back seat. This has made me so mad that I will not buy a Ford again.
By , April 23, 2015
Less then 24 hrs and my window cracks again .. Only went like 2 miles and you could hear like something was vibrating then a pop the a crack coming down the window .. Call safelite asp .. They said will have a manger call me in the morning .. It was only 430 to make appointment to check out the window to see if it was a stress fracture or not . Well the next day came no phone call about 12 o'clock call them back again then today they sent our installer to look at the window and he said it's not a stress fracture . then I talk to the manager he said he will be call me back before the business end of today still sitting here waiting for a call.. The service tech received a phone call while he sitting in his truck and the person ask him what are you doing and he said arguing with this lady she's does not agree on what I said . So then call the number the service tech gave me to advise his boss what he said .. He said something hit it but no one was around us when it happen .. I had a couple of peopl look at said stress fracture . Did the ball point pen and no dip .. Think they just don't want to guarantee their warranty .
By , May 12, 2015
I have a 2012 ford focus with the same problem I went into work at 715 with a normal windshield and by the time I came out side to go home around 430 my windshield had a 3 foot long Crack across the Windshield with no marks from rocks or chips. I've owned my older fords and car and I've never had windshield problems never a chip. But ever since I've bought a new car that it's Cracked the problem is the glass is made thinner and cheaper so they break all the time
By , August 03, 2015
I have had to replace the windshield in my 2014 Ford Fusion TWICE in 4 months! The window replacement tech said they're just making glass lighter (and therefore easier to break) than before. I have never had to replace a windshield in any other car during 30 years of driving.
By , January 18, 2016
I am furious. It is a mild day. I scraped ice, put on the defroster, and drove three miles. Parked. Before I got out of the Forester, I heard a distinct POP in front of me, and looked up to see a crack stretching from under the passenger wiper, up a few inches, across, then down to my side, about the whole width of the glass. I am so mad that everything we buy now is junk. Everything! Where am I going to get a real windshield?
By , January 27, 2016
My Toyota FJ Cruiser got blasted with what I think was coarse sand on the freeway this morning. There are a couple of repairable chips, but the entire thing got pitted and looks like paint overspray landed on it when the sun hits it. The dealership quoted $1200 for OEM glass and my car insurance uses after market glass (or I have to pay the difference). I know several people who have had their FJ windshields replaced with after market glass, but some complain of wavy glass and leaking. Any advice on after market vs. OEM, especially for Toyota?