Expert advice: What to do with a chipped windscreen

You might have noticed many of our roads are in a pretty shocking state. And a degrading road surface doesn’t just mean potholes, it also results in debris on the road surface. These small stones can be thrown up and hit the screen of following vehicles. On a 30mph road, that small stone will probably have an impact speed with the glass at the equivalent of 40-50 mph. It’s hardly surprising then that there’s a decent chance it’ll take a chunk out of whatever it hits.

If debris hits the windscreen and damages it, there are plenty of reasons to get it fixed. After all, if a windscreen is chipped in certain areas it’s an instant MOT failure. Here’s what I think you should do, why, when and how.

Why fix it quickly?

You’ve probably noticed that your insurance policy covers windscreen damage. And that there are two levels: repair and replacement. It might also not have escaped your attention that the excess you pay for repairs is a lot less than that for replacements. The good news is: the sooner it's fixed, the more likely you will need a repair rather than a replacement.

There are also safety implications with a damaged screen. Windscreens on today’s cars are a structural part. Assuming a repair is done properly, your screen will be as good as new.

When chips can be repaired

Unless a chip is in the wrong place (I’ll explain about this below) the sooner a specialist gets to it, the more likely they will be able to repair it. This is because when chips are less than 40mm in diameter, they can be repaired. Bigger than that and the screen needs replacing. If you leave them, as they get dirt and moisture in them, the vibration and changes in temperature will turn the weakest point into a crack. And once that happens, you’re usually on a slippery slope: the crack will spread through the glass like an invading army and you’ll need a new screen.

When chips can’t be repaired

For the purposes of the MOT, the windscreen is split into two sections, the A zone and B zone. The A zone is the central portion of the area swept by the windscreen wiper right in front of the driver. If you have a chip in this it can only be fixed if it’s 10mm in diameter (about the size of a 5p piece) or smaller. Bigger than that and you need a replacement screen.

How to fix it

Broadly speaking, there are three ways to go about rectifying a chipped windscreen. The easiest is to contact your insurer. You’ll pay an excess (the amount you pay for a claim before the insurer’s cover kicks in) that’s usually about £50. However, depending on your insurer and policy it might be nothing. The cover provider will then arrange for their windscreen partner to fix it. This can be done at a location of your choice and usually takes about half an hour.

The DIY repair

The most difficult way is to repair the chipped windscreen yourself. You can buy windscreen repair kits online and from motor retailers. These comprise the resin along with the tools you need to inject it into the chip plus instructions on curing (hardening) the resin. The kits cost about £10 and some people swear by them. But if online reviews are anything to go by, others end up swearing at them…

The third way, which is pretty much the half-way house, is to find an independent company specialising in windscreens. These offer a professional service that takes about half an hour. The difference between that and the insurance route is you go to them. But they cost around £25 so might prove cheaper than the excess you’ll pay your insurer.

Nick Reid is head of automotive technology for Green Flag and is a fellow of the Institute of the Motor Industry