Driver Knowledge Tests

How to know if your car’s windshield is beyond repair

The windshield is the most important protection on your car for preventing bad weather, stones, insects and the occasional large mammal or bird hitting the occupants. A compromised windshield can shatter with a minor impact, showering passengers with pieces of sharp-edged glass.

Many people ignore or disregard small chips and cracks in their windshields, thinking it’s safe to leave them like that, but you can never anticipate when your windshield will finally give in and leave you exposed to all those hazards. It’s often possible to easily repair your windshield, but it’s not always the most effective option.


Chips are minor damage caused by flying debris on the road, and they are easily repaired most of the time. If you have a significant chip in your field of vision, your vehicle may not be deemed to be roadworthy. Large chips can hide hazards on the road, making it more difficult for you to make decisions while driving.

A windshield is made of a layer of glass, then a plastic interlayer, and another layer of glass. If the chip penetrated the first layer and damaged the plastic interlayer, then you may need to replace your windshield. Superficial chips can be filled with an epoxy. There are companies that come out to you and complete it while you wait.


Chips may be hard to spot, while cracks are much easier to spot and harder to repair. Cracks are an obvious line in your windshield and can be as small as a few millimetres, or as big as the whole width of your windshield.

As the vehicle flexes, a small crack can develop into a much larger crack across the windscreen, and even multiple radial cracks. The integrity of your windshield is compromised if you have any cracks in it especially if they are longer than around 100mm. Simple repairs will usually work on small cracks (unless they extend under the edge of the windscreen border), but it is not possible to repair large cracks; the windscreen must be replaced.

Failed repairs

Have you tried to repair your windshield, but the problem still persists? If so, then it’s time for a new windshield. There are two reasons why the windscreen repair didn’t work.

The first reason is that the windscreen is beyond repair as the damage has already compromised the structure of the glass.

The second reason is the repair wasn’t done right. mobile windshield repair advises everyone to check their windshield’s integrity at a professional repair shop to get it right the first time around. It’s important that the repair is carried out to the manufacturer’s specifications as you don’t want the glass to shatter while driving, putting you and other passengers in danger, so if the repair didn’t work,  don’t try to repair it again, and replace it altogether.

Causes of a failed repair are failure to clean the joint, failure to fill the whole crack and failure to let the epoxy cure properly.

Incorrect installation

Sometimes we go for the more affordable option while changing our windshields, but that doesn’t guarantee the best installation. A mistake in the installation can cause uneven pressure on the windshield and leave it vulnerable to crack at the slightest impact or torsion while driving. This problem can’t be repaired, as the integrity of the windshield is already compromised, so the safest option is to replace it and ensure the installation is done properly..

Temperature and weather effects

Our cars suffer through harsh weather. Our weather has a large range – from below freezing to +40C and this causes a lot of expansion and contraction in the glass. If a windscreen is frosty and you use hot water to melt the frost, this can cause rapid expansion which can crack a windscreen that’s already compromised (it usually won’t damage a good quality windscreen with no cracks).

We tend to turn on the heaters during winter, which makes the windshield exposed to cold temperatures on the outside and warm temperatures from the inside. This can gradually degrade the windshield. In winter the windshields are exposed to heavy snow, hail, and salt, which damages the windshields especially if they have cracks and chips.

Frosty windscreens can be cleared easily with hot water, but it’s better to use cold water to avoid cracking the windscreen.

A hole in the windscreen 

This would sound so obvious, but people stick gaffer tape or duct tape on a broken windshield. No one would be able to repair a windshield like this, it should be immediately replaced. A windshield with a missing part will lose more parts quickly, and if one rock hits your windshield, it may cause the windshield to blow up in your face.

This one’s definitely unrepairable.

How to prevent cracks and chips in your windscreen

  1. Check your windscreen when you wash your vehicle – sometimes chips can happen from stones that fly up and you don’t notice them while you’re driving. Truck drivers should check their screen as part of their pre-start inspection.
  2. Attend to any cracks and chips as soon as you can to stop them spreading. 
  3. Slow down when there are road repairs and loose chip on the road’s surface, or where signage indicates stones could be thrown up
  4. If you’re a truck driver, you can purchase a mesh barrier to help stop stones impacting the screen. 
  5. In winter, you can protect the windscreen by parking your car in a garage.
This truck windscreen was shattered by a stone that hit just above the windscreen wiper. A stone guard would have prevented this from happening.

Considerations for your windscreen

Check if your insurance has free replacement glass coverage – some do – and bear in mind that many modern vehicles have a lot of technology either in the windscreen or attached to it, such as cameras, rain sensors and light sensors which make the windscreen more expensive to replace. This is another reason why it’s important to get onto your windscreen replacement quickly.

Darren is an expert on driving and transport, and is a member of the Institute of Advanced Motorists

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