What Causes a Windscreen to Crack or Chip?
A car windscreen can crack or chip suddenly, and it often starts with something small that you barely notice. Even a tiny mark can spread, and it can also affect your visibility when the sun is low or when headlights hit it at night. That is why many drivers ask Will A Cracked Windscreen Fail An Mot before booking a mot test.
Most chips happen due to impacts from rocks, stones, or gravel that are thrown up by the tyres of other vehicles. You cannot stop this risk completely, but keeping a safe gap from the vehicle ahead can reduce how often it happens. Bad weather can also blow debris into the glass, and a fast change in temperature can stress the glass, so do not use boiling water to defrost a frozen windscreen.
Cracks and chips can also be more likely with poor-quality replacement glass or incorrect installation, especially if a windscreen was replaced and not fitted by a skilled technician. If you have a garage, parking your car inside can protect the windscreen from falling branches and harsh weather. While the car is parked, check the windscreen wipers because worn wiper blades can drag dirt across the glass and make the damage worse, which can matter during an MOT.
Damaged and Cracked Windscreen MOT Failure Criteria (Infographic)
How Serious Is a Windscreen Chip or Crack for MOT Standards?
A chip or crack in the windscreen matters for MOT standards because it can affect what the driver can see. Even small marks can create glare from sunlight and headlights, which makes dangers and obstacles harder to spot in time. That is why the tester will look out for a cracked windscreen MOT.
Is a cracked windscreen an mot failure? It can be, because any damage that blocks clear vision can be treated as a safety issue. The windscreen is not only there to keep out wind and rain, but it also supports safe driving by giving a clear view of the road. If the glass is damaged, the car may not meet the standard expected for safe use.
The windscreen also helps support the structure of the vehicle, so it needs to be in good condition. If a windscreen is fitted badly, it may not sit correctly, and that can affect the working of passenger airbags in a crash.
MOT Windscreen Rules Explained: What Testers Look For
During a MOT, the tester inspects the windscreen crack MOT failure risk factors that affect visibility, such as the glass, wipers, and washers. If these components do not function properly, the vehicle may be considered unsafe to drive.
Wipers must be secure, in good condition, and able to clear the screen well. If the blades are worn, the arms feel loose, or the wipers leave streaks and do not clear the glass properly, you could fail the MOT. Clear visibility of the road matters in every kind of weather, even on a short trip.
Washers are checked too because they work with the wipers to remove dirt and dust from the windscreen. You can fail if the washers don’t spray properly (for example, due to empty fluid or blocked jets). It is advisable to test the washers at home and replace the blades if they do not clear the glass properly.
For more guidance on what you can legally check yourself before an MOT test, see our guide: can an mot be done at home?
When Does a Cracked Windscreen Become an MOT Failure?
A cracked windscreen becomes an MOT failure when the damage is large enough or when it is in the wrong place. In the event of a crack in windscreen MOT, the tester looks at the size of the chip or crack and whether it affects the driver's view of the road while driving. Even a small crack can become a bigger problem if it spreads.
If the damage is in the driver’s direct line of sight, the limit is very strict. A chip or crack that is over 10mm in that viewing area can fail an MOT. This rule exists because anything in that zone can block vision and delay your reaction to dangers.
For the rest of the windscreen, the allowed limit is larger, but it still matters. If a chip or crack is over 40mm in diameter anywhere outside the main viewing area, it is an immediate fail. If you spot damage before the test, it is usually best to repair or replace the windscreen early, so you avoid a failure and keep the car safe to drive.
Can You Drive Legally With a Cracked or Chipped Windscreen?
Driving with a cracked or chipped windscreen is illegal if the damage impairs safe driving. The Highway Code requires drivers to have a clear view of the road ahead, and it also recommends that you check the condition of your glass to ensure that it remains safe and roadworthy. If a crack obscures your view, you may be charged with operating a vehicle in dangerous conditions.
If you’re stopped, you may receive a fine and could receive penalty points, depending on how badly the damage affects visibility. The risk is higher if the damage is in the driver’s line of sight, because it can obscure hazards and make glare worse. This can also make your car fail its MOT, since visibility is a key safety standard.
A damaged windscreen can also cause bigger problems after an accident. If you crash while the windscreen is already cracked, the police may treat it as a more serious offence. For the same reason, it is smart to deal with a crack on windscreen MOT issue early, rather than ignoring it and hoping everything will be alright.
Will a Cracked Windscreen Lead to Penalty Points or Fines?
A cracked windscreen does not usually lead to penalty points or a fine during the MOT itself. What the tester can do is record the damage, or fail the car if the crack is too big or in a risky place. As a quick windscreen crack mot guide, the MOT inspection focuses on visibility and uses clear size and location limits to decide whether the glass is safe.
The tester divides the windscreen into zones, and Zone A sits directly in front of the driver, centred on the steering wheel with its middle above it. If a chip or crack in Zone A measures more than 10mm, it is treated as a visibility risk and can cause a cracked windscreen fail.
The remaining glass is Zone B, where damage above 40mm in diameter anywhere on the screen is an immediate MOT failure. Smaller marks in Zone B may be recorded even when you pass, because they can spread over time, so it is sensible to fix them before they turn into a larger crack.
Can a Windscreen Chip or Crack Spread Before Your MOT?
Yes, a windscreen chip or crack can spread before your MOT, and it usually happens faster than you would expect. A small chip can gradually grow into a longer crack, especially when the glass is stressed by vibration, wind, and daily driving. The damage will not heal on its own, so it is best to treat it as a time-sensitive situation.
Small damage is usually easier and less expensive to repair than a completely cracked windscreen that requires replacement. Many chips can be sealed by a technician with clear epoxy or acrylic resin, which helps to keep dirt and moisture out. Larger cracks are more difficult to repair, often requiring a more complicated repair or a complete replacement.
If your MOT date is close, do not wait, even if the damage is not in your direct view. A crack that is left alone can spread across the glass and lead to a failure. Sorting it early can also help you avoid last-minute stress around an MOT windscreen crack check.
You can also lower the chance of damage getting worse with a few simple habits. In cold weather, do not pour hot or boiling water on a frozen windscreen, because quick temperature changes can crack glass. Replace windscreen wipers about once a year, and check the screen often so you can arrange repairs early if you spot new marks.
Road conditions also play a big part, so drive carefully on rough roads and through roadworks where loose stones can get kicked up. Leave a good gap between your car and the one ahead, because that gives stones less chance to fly up and hit your windscreen. You cannot avoid every chip, but these habits can help stop a small mark from turning into a larger crack before your MOT.
How Much Does It Cost to Repair a Windscreen Chip?
A windscreen chip repair is usually inexpensive, but the cost varies depending on the severity of the damage. Most basic chip repairs cost between £40 and £120, and many insurance policies cover this type of work. It is worth calling your insurer to see what your policy includes.
It also helps to act quickly. A small chip can spread into a crack, and repairs tend to cost more once the damage gets bigger. If the windscreen needs replacing, prices often start at £100 and can reach £400 to £500 on some high-end cars.
Windscreen Chip Repair vs Replacement: What’s the Best Option?
The appropriate choice is determined by the size and shape of the damage. A small chip is often easy to repair, but a large chip or a long crack usually indicates that the windscreen needs to be replaced. It is smart to deal with it early because chips can spread and turn a quick repair into a bigger, more expensive fix.
If the chip is small, you may be able to fill it with resin using a repair kit, or you can take the car to a technician. In most cases, a technician is the safer choice, because a poor repair might not seal the damage properly, and the crack can grow over time.
Replacement becomes more likely when the chip is large or when the crack keeps spreading. A new windscreen costs more, but it may be the only reliable fix once the glass is badly damaged. Sorting it early can also help you avoid problems like an MOT cracked windscreen fail. Check if the damage gets worse before your test.
Can Car Insurance Cover Windscreen Repair or Replacement?
Yes, car insurance can sometimes cover windscreen repair or replacement, but it depends on your policy. Some policies let you claim for a damaged or cracked windscreen, and in certain cases, it may not affect your no-claims bonus.
There can be exceptions, so it is best to contact your insurer as soon as you notice any damage. Enquire about what your policy covers, what you may have to pay, and whether the claim affects your bonus. That way, you know where you stand before you book the repair.
Do Side Windows, Rear Windows, or Wing Mirrors Affect MOT Results?
Yes, side windows and wing mirrors can affect MOT results because the tester checks whether you can see clearly around the vehicle. The windscreen is the main focus, but anything that blocks your view can become a safety issue. This includes damage that creates distortion or heavy scratching, not only large cracks.
Front side windows are important because they help you see what is beside you and behind you, especially at junctions and when changing lanes. If a front window is badly cracked or heavily scratched, it can interfere with your view and may lead to a fail. Even if you do not rely on those windows all the time, it is usually safer to fix obvious damage before the test.
Mirrors are checked in the same way, since they are essential for seeing the road behind you. The tester will check that the interior mirror and the external mirrors give a clear view with no serious distortion. A cracked wing mirror can cause a fail if the crack is bad enough that you cannot see properly, so if you are unsure, replacing it before the MOT can save you trouble.
Pre-MOT Windscreen and Mirror Checklist
Before your MOT, do a quick check of your windscreen, windows and mirrors to ensure that the tester can see clearly in all important directions. Start with the mirrors, since they are essential for seeing what is behind you and beside you. A few minutes at home can save you from problems on test day.
Clean the interior mirror and both side mirrors so they give a sharp, clear view. If a mirror is cracked or badly scratched, replace it, because heavy damage can distort what you see and may cause an MOT fail. Also, make sure the mirrors are secure and correctly positioned.
Next, clean the front side windows, since they help you see traffic and hazards at junctions and when changing lanes. If those windows are heavily scratched or cracked, it is safer to fix them before the test. Rear side windows are less critical for driving view, so small damage there is usually less of a concern, but keeping them clean is still a good habit.
Read our guide on things to check before an mot
Expert Tips to Prevent Future Windscreen Damage
- Avoid gravel roads and busy construction areas when you can, because loose stones are a common cause of chips. If you must drive through them, slow down so debris is less likely to fly up and hit the glass.
- Leave plenty of space behind the vehicle in front, especially on rough roads. A bigger gap reduces the chance of stones being thrown up by their tyres and striking your windscreen.
- Check your windscreen wipers often, and replace them if they are worn or damaged. Rough blades can drag gravel across the glass, exacerbating small chips or scratches over time.
- When possible, park under a shelter, such as a garage or carport. This protects your windscreen from bad weather and lowers the risk of damage from falling branches.
- Do not defrost a frozen windscreen with boiling water. A sudden temperature change can stress the glass and increase the chance of cracks forming.
- It's best to avoid driving in really bad weather if you can help it, especially when there are strong winds or storms. You never know when flying debris or falling branches might come out of nowhere and damage your windscreen.
FAQs
How long is it safe to drive with a cracked windscreen?
If you have a cracked windscreen, it is safest to only drive if you need to get the glass repaired or replaced. A crack can spread quickly, and if it affects your view, it may also be illegal to keep driving. If the crack is in your line of sight or is growing, avoid driving and arrange a repair as soon as you can.
How can a cracked windshield be repaired?
A small chip can sometimes be repaired by injecting a clear resin that seals the damage and helps stop it from spreading. Larger cracks are harder to fix and often mean the whole windscreen needs replacing. It is best to speak to a professional technician or your insurer, because a poor repair may not hold, and the damage can get worse.
How do you prevent a windscreen crack from spreading?
To stop a crack from spreading, get it repaired as soon as you can. Try to avoid sharp temperature changes, like pouring boiling water on a frozen windscreen, and keep a safe distance from other cars to reduce the chance of stones hitting the glass. A crack can still grow even if you are careful, so do not put it off.
Does a cracked windscreen fail MOT?
Is a cracked windscreen an mot fail? Yes, a cracked windscreen can fail an MOT, depending on the size and where it is. If the damage is over 10mm in the driver’s direct line of sight, or over 40mm anywhere else on the windscreen, it will fail. Smaller damage may be noted, because it can spread and become a bigger issue later.
Can a Mot Check show past windscreen damage or advisories?
An online Mot Check can show past MOT results and any advisories that the tester recorded. If windscreen damage was serious enough to note, it may appear, but small chips fixed between tests will not be listed.
Does a car history check include previous windscreen replacements or claims?
A car history check may show some insurance events, such as an accident claim, a write-off category, or theft records. It usually does not list routine windscreen replacements or small glass claims, because these are not always reported to the databases used for checks. If you need certainty, ask the seller for invoices or contact the insurer for claim details.
