Can you drive with a chipped windscreen, will it fail the MOT, and what should you look for on the glass of a used car before you buy?

Quick answer: A small chip outside the driver's line of sight is not usually an MOT fail. Damage bigger than 10mm in the area directly in front of the driver, or bigger than 40mm anywhere else the wipers sweep, can be. The law says the glass must not obscure your view while you drive. Small chips can often be repaired with resin, but frost, hot water and potholes can turn a chip into a crack. On a used car, look closely at the screen, check the MOT history, and ask about the camera if the windscreen has been replaced.

Frosty mornings are on the way, and that is when chips tend to spread. A chip you can live with in October can become a crack across the screen by Christmas.

At anycolourcar.com we sell quality used vehicles from The Old Garage on Genn Lane in Worsbrough, and our own technicians prep every car and van at our Stairfoot service centre. This guide is what we would want any buyer around Barnsley, Sheffield, Wakefield and Rotherham to know, whoever they buy from.

Looking for your next car or van? Start on car search or call sales on 01226 574410.

Is it illegal to drive with a chipped or cracked windscreen?

It can be. Regulation 30 of the Road Vehicles (Construction and Use) Regulations 1986 says all glass on a vehicle must be kept in a condition that does not obscure the driver's vision while it is being driven on a road.

Rule 229 of the Highway Code adds that before you set off you MUST be able to see, so you must clear all snow and ice from all your windows.

The RAC says driving with a cracked windscreen may be an offence if the damage blocks your view of the road or makes the car unsafe. GOV.UK says you can be fined, banned from driving and get 3 penalty points for driving a vehicle in a dangerous condition, and that a car can be unsafe even with a current MOT.

So a tiny chip low down on the passenger side is a very different thing from a crack running across your view.

Will a chipped windscreen fail the MOT?

It depends on the size of the damage and where it is. The MOT inspection manual tells testers to sit in the driver's seat and look for:

damage in zone A more than 10mm across
damage in the rest of the windscreen's swept area (the part the wipers clear) more than 40mm across
damage to the windows on either side of the driver's seat

Zone A is a band 290mm wide, centred on the steering wheel, inside the swept area. In other words, the part of the screen you look through most.

The manual says a failure for damage is only justified if it significantly affects the driver's view of the road. Damage that does not affect the view can be recorded as a minor defect, which does not fail the test. The AA adds that damage outside the swept area will not fail the MOT, but you may still be advised to get it fixed.

Two more points are worth knowing. A repair that is invisible or barely detectable, finished flush with the glass, does not count as damage. And the government guidance on windscreen obscuration says a crack that passes through the swept area and reaches the edge of the screen at two points makes the windscreen insecure.

Can a windscreen chip be repaired?

Often, yes, if you act quickly. The AA says that in zone A only damage up to 10mm wide can be repaired, and elsewhere on the windscreen a chip up to 40mm wide can be repaired.

A repair means cleaning and drying the chip, then filling it with a clear resin. The RAC explains that this seals the chip and stops moisture and dirt getting in. The AA is honest that the damage will not completely disappear, but the chip will be less visible and have a smooth surface.

Do not wait. The AA says dirt or moisture in a chip makes a good repair harder, and a small chip can grow until it cannot be repaired. The RAC says a cracked windscreen is often a chip that was left and grew, and a full crack will usually mean a new windscreen.

Why do chips turn into cracks in winter?

The AA says cracks can form through the combined effects of heat, frost, dirt and vibration. Cold weather brings a few extra risks:

Hot water on a frozen screen. The AA's defrosting guide explains that glass expands quickly when warm water touches it and contracts as it cools in the cold air. That flexing can crack the glass even with lukewarm water, especially if there is already a chip.
Using the wipers as a scraper. The RAC says this strains the wiper motor and can tear or blunt the blades.
Potholes. The AA says the shock of hitting a pothole can make an existing crack worse.
Ice and grit. The AA lists stones and grit as the most common cause of chips and cracks, along with hail and chunks of ice coming off other vehicles.

Until a chip is fixed, the AA suggests warming the screen gradually in cold weather and not slamming the doors, as the sudden pressure change can make a chip crack. The RAC adds that keeping a sensible distance from the vehicle in front and driving carefully on poor roads and roadworks helps avoid chips in the first place.

What about the camera behind the windscreen?

Many newer cars have a camera or sensor mounted on the windscreen, often around the rear-view mirror. It can work features such as lane-keeping assistance, automatic emergency braking, rain-sensing wipers and automatic dipping headlights. Our guide to car safety features and acronyms explains what these systems do.

The Institute of the Motor Industry points out that even a windscreen replacement may involve these sensors. If they are not calibrated afterwards, the result can range from wipers that no longer detect rain to safety systems that do not work as they should.

Thatcham Research's code of practice for windscreen replacement says customers should be told not to rely on these systems after a windscreen change until they have been calibrated, and that the customer should be given a copy of the calibration certificate.

The RAC also notes that the windscreen is an essential part of the car's structure, and that an incorrectly fitted windscreen could interfere with the passenger airbag. So a replacement screen is worth asking about.

What to check on the windscreen of a used car

Look at the glass in daylight if you can, from the outside and from the driver's seat. Work through these on the viewing or the test drive:

Sit where the tester sits. From the driver's seat, look through the area the wipers sweep. Any chip or crack in front of the steering wheel deserves a closer look.
Look along the edges. Check around the edge of the screen for cracks, and for any crack running from one edge towards another.
Count the chips. Look for small stone chips across the whole screen, not just in front of you. Ask whether any have been repaired.
Check the wipers. Run the wipers and washers. They should clear the screen without smearing. Fine scratches or arcs in the glass can make glare from the sun and headlights worse, as the RAC points out.
Look for the safety glass marking. The MOT manual says safety glass can be identified by markings such as an E mark with the number 43R, or a small e mark followed by a number inside a square. It is usually in a lower corner of the screen.
Check the MOT history. The GOV.UK MOT history checker shows what failed at each test and any minor problems. Our guide to what an MOT advisory means explains how to read them. A windscreen advisory last year is worth asking about now.
Ask about a replacement screen. If the windscreen has been changed and the car has a camera on the glass, ask whether it was calibrated and whether there is a certificate.

If you find a chip or crack, ask the seller what they are doing about it before you pay, and get any promise to fix it in writing. Our used vehicle test drive checklist covers the rest of the bodywork and glass.

What we do before a vehicle leaves us

Every car and van at anycolourcar.com is prepared by our own technicians at our Stairfoot service centre in Barnsley.

Every vehicle we sell comes with a brand-new 12-month MOT, booked and paid for by us at a local DVSA-approved testing station, plus 6 months' warranty and 12 months' AA breakdown cover on every retail sale. That means the windscreen has been checked against the MOT glass rules above before you collect it.

If you spot a mark on the glass of a car you are viewing with us, point it out and ask. We will tell you what it is and what is being done about it.

We do not pay sales commission, so you get straight answers and no pressure. Part exchange is welcome. If you cannot get here in daylight, we can send a walk-around video.

A small chip is cheap to deal with early and a pain to ignore. Look at the glass, check the history and ask the question before you buy.

FAQ

Can you drive with a chipped windscreen?

Yes, as long as the damage does not obscure your view of the road. The law says the glass must not obscure the driver's vision, so a chip in your line of sight or a crack across the screen is a different matter. Get it looked at quickly before it spreads.

Will a chip on the passenger side fail the MOT?

Not usually. Outside zone A, damage in the swept area only becomes a fail when it is more than 40mm across and significantly affects the driver's view. Damage outside the swept area does not fail the MOT, but you may be advised to get it fixed.

Does car insurance cover a chipped windscreen?

It may. The AA says windscreen damage may be included in a comprehensive policy but not in a third party, fire and theft policy, and you will usually pay an excess. Check with your insurer before booking a repair.

Should I use hot water to defrost my windscreen?

No. The AA says hot or even lukewarm water can make the glass flex and crack, especially if it already has a chip. Use the heater, a scraper and de-icer instead.

Will a repaired chip disappear?

Not completely. The AA says a resin repair leaves the chip less visible with a smooth surface. For the MOT, a repair that is invisible or barely detectable and finished flush with the glass does not count as damage.

In short

A chip in the glass is easy to ignore until frost or a pothole turns it into a crack. The MOT looks hardest at the 290mm band in front of the steering wheel, where damage over 10mm can fail, and at the rest of the swept area, where the limit is 40mm. Small chips can often be repaired if you act quickly. On a used car, look closely at the screen, check the MOT history and ask about any replacement windscreen and camera calibration.

For the rest of the viewing, use our used car buying checklist for Barnsley and our guide to buying a used car in winter.

Ready to look? Browse car search or call sales on 01226 574410.

Hero image: photo of a cracked car windscreen by Famartin, CC BY-SA 4.0, cropped and placed beside our own graphic.

anycolourcar.com · The Old Garage, Genn Lane, Worsbrough, Barnsley S70 6TF · Sales 01226 574410

Chipped or cracked windscreen? MOT rules and checks on a used car in Barnsley