Will a Cracked Windscreen Fail an MOT?

You spot a chip in your windscreen and tell yourself you’ll deal with it later. A few weeks pass, the weather turns colder, and suddenly that tiny mark has become a crack stretching across the glass.

Sound familiar?

It’s one of the most common issues drivers notice in the weeks leading up to an MOT. The problem is that many motorists aren’t sure whether windscreen damage is simply cosmetic or something that could lead to a failed test.

The answer depends on more than just the size of the crack. MOT testers look at where the damage is located, how much of the driver’s view it affects, and whether it falls within specific areas of the windscreen covered by DVSA regulations.

At TJ Services, we regularly speak with drivers from Fleet, Aldershot, Farnborough, and the surrounding areas who are unsure whether a chip or crack will cause problems at their upcoming MOT. In many cases, what looks minor can be enough to fail. In others, a surprisingly large crack may still pass depending on where it sits.

This guide explains exactly what MOT testers look for, when windscreen damage becomes a failure, and what you can do before test day to avoid any unwelcome surprises.

What MOT Testers Actually Look for on Your Windscreen

When a vehicle goes through its MOT, the tester examines the windscreen against a specific set of criteria. It is not a simple pass or fail based on whether a crack exists. It comes down to location, size, and how the damage affects the driver’s view of the road ahead.

The windscreen is divided into two zones for MOT assessment purposes.

Zone A sits directly in front of the driver, covering a 290mm wide area centred on the steering column within the wiper-swept area. This is the critical zone. Any damage here larger than 10mm results in a Major fault and an automatic MOT failure.

Zone B covers the rest of the wiper-swept area outside of Zone A. Damage larger than 40mm in this zone will also fail the vehicle.

Outside the wiper-swept area entirely, damage is assessed on whether it significantly obstructs the driver’s view. A crack confined well outside the swept zone and away from sight lines may not cause a failure at all, though a tester could still record it as an advisory if it shows signs of spreading.

Zone	Location	Maximum Permitted Damage Size
Zone A	Central 290mm directly in front of driver	10mm
Zone B	Remaining wiper-swept area outside Zone A	40mm
Outside swept area	Edges, corners, periphery	Assessed on obstruction to view

The 10mm Rule: Smaller Than Most Drivers Expect

The 10mm rule is the one that catches most drivers off guard. Ten millimetres is roughly the size of a fingernail. That is smaller than most people picture when they think of a windscreen crack. If you have a chip or crack sitting in Zone A that measures more than that, the vehicle will not pass its MOT.

This rule exists because Zone A is where your eyes naturally rest when driving. Any distortion, glare, or obstruction in that space directly compromises your ability to see hazards, pedestrians, and road markings ahead. Drivers across Farnborough and Fleet regularly deal with stone chips from faster A-road driving, and what looks like a minor blemish can quickly tip into failure territory once it is properly measured.

It is also worth knowing that even a chip smaller than 10mm in Zone A can still fail if the tester judges it causes significant visual distortion. Size is a guide. Clarity is the standard.

Does a Crack Always Mean an MOT Failure?

Not automatically, no. The location of the damage matters more than the mere presence of a crack. A long crack running along the very bottom edge of the windscreen, below the wiper sweep and well away from the driver’s direct line of sight, may not cause a failure at all. A small chip near the top corner by the roof line could pass without issue.

What testers are looking for is whether the damage impairs safe driving. The MOT inspection manual on GOV.UK makes clear that windscreen defects are assessed on the basis of whether the driver’s view is significantly impaired. If it is, the vehicle fails. If it is not, the damage may still be recorded as an advisory.

Drivers coming through from Ash, Tongham, and the surrounding villages often ask whether an advisory means they can still use the car. Yes, an advisory means the vehicle passed but the issue should be monitored and addressed. It is not a legal requirement to fix it immediately, but leaving it is a risk that tends to grow over time.

Common Causes of Windscreen Damage Before an MOT

Understanding how windscreen damage happens helps you catch problems early, before a minor chip becomes an MOT failure. The most frequent causes are worth knowing before you arrive at your test.

1. Stone chips from A-roads and dual carriageways, particularly common on routes through North Camp and Farnham where higher speeds throw up more road debris
2. Thermal stress caused by overnight temperature drops, which forces existing chips to crack outward through the glass
3. Worn or frozen wiper blades dragged across the screen, leaving fine scratches that worsen under repeated use
4. Poor quality chip repairs where the resin was not properly applied, leaving the damage vulnerable to cracking again
5. Structural movement in older vehicles where worn screen seals allow slight flex under braking, turning a stable chip into a spreading crack

Catching a chip early is one of the most straightforward things a driver can do to protect an MOT result. A chip repaired before it spreads typically takes less than an hour to fix. Once it becomes a full crack, replacement is usually the only remaining option.

Chip vs Crack: Why the Distinction Matters for Your MOT

There is a practical difference between a chip and a crack that goes beyond appearance. A chip is an impact point where a small piece of glass has been displaced or broken away. A crack is a line fracture that extends outward from a point of stress, sometimes travelling several centimetres across the screen.

For MOT purposes this distinction is important to understand. A chip in Zone A that measures under 10mm can potentially pass. But a chip that has cracked outward is measured by the total length of the fracture, not just the original impact point. A 6mm chip that has grown a 25mm crack sitting within Zone A will fail, even though the chip itself was originally small enough to pass.

Repairing a chip before your MOT is one of the most practical steps a driver can take. Repair resin fills the damage, stops further spreading, and in most cases restores enough optical clarity to satisfy an MOT tester. A repaired chip does not automatically fail. Testers assess whether the repair itself causes any visual distortion that would impair driving.

What Happens If Your Windscreen Fails the MOT?

If your windscreen causes an MOT failure, the vehicle is issued a Fail certificate. You cannot legally drive the car on public roads in its current condition unless you are travelling directly to a pre-booked repair appointment.

Here is what the process looks like after a windscreen-related MOT failure.

1. You receive a VT30 refusal of MOT certificate detailing the reason for failure
2. You arrange windscreen repair or full replacement depending on the extent of the damage
3. Once repaired, the vehicle is retested, either as a partial retest covering only the failed items or as a full retest if more than ten working days have passed since the original test
4. A new pass certificate is issued once the vehicle meets the required standard

Drivers in Aldershot and Ash Vale who fail on windscreen damage often find that a same-day or next-day repair followed by an immediate retest is the quickest route back to a valid MOT. Booking the repair through the same garage conducting the MOT, where possible, tends to make the process smoother and faster.

Windscreen Damage Fault Categories Explained

MOT faults are now classified into three categories following the updated testing standards introduced in 2018. Understanding these categories helps you know how seriously a tester will view your windscreen damage.

Dangerous faults mean the vehicle poses an immediate risk to road safety. These result in an automatic fail and the vehicle must not be driven until repaired. Severe windscreen damage that completely obstructs the driver’s view could be classified here.

Major faults mean the vehicle has a defect that may affect safety or the environment. These also result in an automatic fail. A crack larger than 10mm in Zone A falls into this category.

Minor faults, previously called advisories, are recorded but do not cause a failure. Small chips outside Zone A or very minor surface marks may fall here depending on the tester’s assessment.

Fault Category	Effect on MOT Result	Typical Windscreen Example
Dangerous	Automatic fail, vehicle must not be driven	Severely shattered or obscured screen
Major	Automatic fail	Crack over 10mm in Zone A
Minor	Recorded, vehicle passes	Small chip outside swept area
Advisory	Recorded, no immediate action required	Spreading chip at screen edge

How to Check Your Windscreen Before the MOT

Giving your windscreen a proper check before your test takes less than ten minutes and could save you a failed test, a rebooking fee, and the cost of an unplanned repair. Here is a straightforward process to follow.

1. Clean the glass thoroughly on both sides so nothing is masked by grime or smearing
2. Sit in the driver’s seat and look straight ahead through the full wiper-swept area at a light source or bright sky
3. Check the central zone directly in front of you very carefully for any chips, cracks, or distortion
4. Use a coin or ruler to get a rough sense of whether any damage is approaching 10mm within that central area
5. Check the broader wiper-swept area beyond that central zone for anything approaching 40mm in length
6. Look along the edges of the screen for any cracks that are working their way inward toward the swept area
7. Check the screen surround and rubber seal for any lifting or gaps that could affect the structural integrity of the fitting

If you spot anything you are unsure about, getting it assessed by a professional before your test is always the right call. A garage in Fleet or Farnborough can usually give a quick visual opinion on whether a chip is likely to be an issue before the official test takes place.

Repair or Replace: Which Does Your Windscreen Need?

This is the practical question most drivers face once damage is confirmed. The answer comes down to the size, depth, and location of the damage rather than personal preference or cost.

Repair is usually suitable when:

The damage is a single chip or short crack under 40mm in total length, it has not spread into Zone A beyond the 10mm limit, the chip has not penetrated through both layers of the laminated glass, and the damage is not directly in the driver’s primary line of sight.

Replacement is usually required when:

The crack exceeds 40mm anywhere in the wiper-swept area, damage sits in Zone A and measures over 10mm, multiple chips have created a network of cracks across the screen, or the structural integrity of the laminated glass has been compromised.

For drivers in Farnham and surrounding areas, getting a professional assessment quickly after any stone strike gives you the best chance of a repair rather than a full replacement. The longer a chip is left, especially through cold nights, the more likely it is to crack outward and become unrepairable.

Does Windscreen Tinting or Stickers Affect the MOT?

Yes, they can. Tinted windscreens and adhesive items placed on the glass are assessed during the MOT under the same principle of whether they impair the driver’s view.

Factory-fitted tinted windscreens that comply with legal light transmission requirements will not cause an issue. Aftermarket tint film applied to the windscreen is a different matter. If it reduces light transmission below the legal minimum or causes significant visual distortion, it will fail.

Stickers, parking permits, air fresheners, and dashcams mounted to the windscreen can also be flagged if they sit within the wiper-swept area and obstruct the driver’s view. A dashcam fitted centrally behind the rear-view mirror in the top portion of the screen generally falls outside Zone A and is unlikely to cause a problem. Anything mounted low and centrally needs to be repositioned before the test.

Drivers coming through from Tongham and Ash for their annual test often overlook this. A quick clear-out of anything stuck to the inside of the screen before the appointment is a simple habit worth building.

What the MOT Does Not Check on Your Windscreen

Knowing the boundaries of what the MOT covers helps set realistic expectations. The MOT is a minimum safety standard check, not a comprehensive condition report on your vehicle.

The MOT does not assess:

The cosmetic appearance of fine surface scratches that do not impair vision, chips or cracks sitting entirely outside the wiper-swept area that do not obstruct the driver’s view, the age or clarity of older glass that has become slightly hazy from years of wiper use but still meets the visibility standard, or minor marks left by a repaired chip that passed the optical clarity test at the time of repair.

None of these will cause a failure on their own. What the test is focused on is the driver’s ability to see the road clearly and safely. If the glass allows that, the test moves on.

Keeping Your Windscreen MOT-Ready Year Round

Looking after your windscreen throughout the year rather than only in the weeks before your MOT is a far more sensible approach. A few consistent habits make a real difference.

1. Deal with any stone chip within the first few days of it appearing, before temperature changes cause it to spread
2. Replace wiper blades at least once a year, or sooner if they begin to smear or judder across the glass
3. Use a proper screen wash solution rather than plain water, which freezes in cold weather and can stress the glass
4. Avoid pouring hot water onto a frozen screen, as the rapid temperature change is one of the most common causes of sudden cracking
5. Park away from direct sun where possible during summer months, as heat builds up inside a parked car and puts stress on already damaged glass
6. Check the rubber seal around the screen periodically, as any lifting allows water ingress which weakens the bond and increases flex

Drivers across Aldershot, Farnborough, and the wider area deal with a range of weather conditions across the year that put windscreens under pressure. Making these checks part of your regular routine means you are far less likely to arrive at your MOT in Fleet with a crack that could have been a cheap repair six months earlier.

How Windscreen Issues Connect to the Wider MOT Picture

A windscreen failure does not happen in isolation. It is part of a broader MOT assessment that covers dozens of components across the vehicle. Arriving at your test with a known windscreen issue is one of the more avoidable failures, because unlike brake wear or suspension deterioration, glass damage is visible and easy to assess in advance.

Understanding common MOT failures helps you build a more complete picture of what testers are looking for across the whole vehicle, not just the windscreen. Lights, tyres, brakes, and emissions are among the most frequently failed categories, and like windscreen damage, most of them give visible warning signs before test day.

If your vehicle is also due a service, it is worth understanding the difference between the two appointments. An MOT and a service serve different purposes, and combining them intelligently saves time and keeps the car in better overall condition throughout the year.

What to Do If You Are Unsure About Your Windscreen

If you are sitting with a crack or chip and genuinely unsure whether it will pass, the most practical step is to get a pre-MOT inspection before committing to the test booking. A quick visual check by a qualified tester takes only a few minutes and gives you a clear answer before any money changes hands.

Garages in the Fleet and North Camp area that offer pre-MOT checks can give you an honest assessment of the windscreen alongside any other items that might be borderline. That conversation costs nothing and could save you a failed test fee plus an unplanned repair.

If you already know the damage is borderline, getting the chip repaired before the test is nearly always the right call. Repair is faster, less disruptive, and in most cases resolves the issue entirely. Arriving at the test with a freshly repaired chip is a far better position than hoping a tester measures it differently on the day.

Conclusion

A cracked windscreen does not automatically mean an MOT failure. But it absolutely can, and the margin between a pass and a fail is tighter than most drivers realise. The 10mm rule in Zone A, the 40mm limit in Zone B, and the broader principle of whether your view is impaired are the three things every driver needs to carry in their head.

The good news is that most windscreen damage, if caught early, is repairable. A chip addressed within a few days is almost always a quick, straightforward fix. A crack left to spread through cold nights and A-road vibration is a different problem entirely.

Check your glass before your test. Get any chips repaired promptly. And if you are unsure, ask a professional before test day rather than on it.

Frequently Asked Questions

Will a small chip in the centre of my windscreen fail an MOT?

It depends on the size and location. Any chip larger than 10mm in Zone A, the central 290mm area directly in front of the driver, will result in a Major fault and an automatic failure. A chip smaller than 10mm may still fail if a tester judges it causes significant visual distortion.

Can I drive my car after a windscreen MOT failure?

You can only drive it to a pre-booked repair appointment. Driving a vehicle with a failed MOT on public roads for any other purpose is illegal and will invalidate your insurance.

Does a repaired chip affect my MOT result?

Not automatically. A repaired chip is assessed on whether the repair causes any visual distortion. A good quality repair that restores optical clarity will typically pass. A poorly filled chip that has cracked again or left visible distortion in Zone A could still fail.

How long does windscreen replacement take before I can book a retest?

Most professional replacements use a fast-cure adhesive that sets within an hour, but the full bond typically requires one to two hours before the vehicle is safe to drive. Your retest can usually be booked the same day or the following morning.

What is the difference between a Major fault and an advisory on the windscreen?

A Major fault means the vehicle has failed and cannot be used on the road until repaired. An advisory means the damage was noted but did not meet the threshold for failure. Advisories should be addressed promptly as they indicate an issue that is likely to worsen.

Does a dashcam on the windscreen affect my MOT?

A dashcam mounted centrally at the top of the screen behind the rear-view mirror is unlikely to cause a problem. Any device mounted low and centrally within the main swept area could be flagged if it obstructs the driver’s view, so repositioning it before the test is advisable.