A small chip can be sealed before it spreads into a crack that weakens the whole windscreen
A windscreen chip is a small break in the glass, usually the size of a coin or smaller, caused by a stone or debris hitting the surface while you drive. The damage starts at the impact point and can spread into a long crack within days or weeks, especially if you hit a pothole, brake hard, or experience temperature swings. Repairing a chip while it is still small costs far less than replacing the entire windscreen and keeps the glass structurally sound.
The repair process involves injecting a clear resin into the chip, which hardens and bonds the glass back together. This works best on chips that have not yet cracked outward, and it restores enough strength that the windscreen will not fail in a collision or from pressure changes. Once a chip becomes a crack longer than about 30 centimetres, or spreads toward the edge of the windscreen, repair is no longer possible and replacement becomes necessary.
Key Takeaways
- Windscreen chips should be repaired within a few days of the damage, before temperature changes or road vibration cause the chip to spread into a crack.
- Resin injection repair costs significantly less than full windscreen replacement and can be done at a glass repair shop or sometimes at your home.
- The repair works by filling the chip with hardened resin that bonds the glass and restores structural integrity, though the glass will never be completely invisible at that spot.
- Chips in the driver's direct line of sight may need replacement rather than repair depending on your local road safety rules and insurance policy.
- After repair, the windscreen needs time to cure before you drive, and you should avoid car washes and heavy rain for at least 24 hours.
How windscreen chip repair actually works
The repair technician first cleans the chip thoroughly to remove any dirt, moisture, or loose glass fragments. They then explore a special adhesive around the damaged area and inject a two-part resin (usually an epoxy or polyurethane compound) directly into the chip using a syringe or pressure applicator. The resin flows into all the tiny fractures within and around the chip, filling the voids where air pockets would otherwise weaken the repair.
Once the resin is injected, it is left to cure. Curing time varies by product—some resins harden in 24 hours, others in 48 hours or longer. During this time, a chemical reaction causes the resin to solidify and bond to the glass on all sides. The technician then removes excess resin from the surface, polishes the area, and checks that the repair is solid. The result is a chip that is structurally sound but may still show a slight discoloration or haze at the repair site, depending on the angle of light and the quality of the resin used.
When repair is possible and when replacement is necessary
Repair is possible if the chip is smaller than about 2.5 centimetres across, has not yet cracked outward from the impact point, and is not touching the edge of the windscreen. If the chip has already begun to spread into a crack, or if the crack is longer than 30 centimetres, the structural integrity of the windscreen is already compromised and repair will not hold. In those cases, the entire windscreen must be replaced.
Location matters as well. If the chip is directly in your line of sight as the driver—roughly in the central third of the windscreen at eye level—your local road safety authority may require replacement rather than repair. Different regions have different rules about what damage is acceptable in the driver's vision area. Check your local road safety rules or ask your insurance provider whether a chip in that location can be repaired or must be replaced.
Temperature and time also affect whether repair is still an option. A chip that sits unrepaired for weeks is more likely to have spread into a crack by the time you seek repair. Cold weather and rapid temperature changes (such as using hot water to defrost a windscreen) accelerate crack growth. The sooner you have a chip repaired after the damage occurs, the more likely the repair will succeed.
Where to have a windscreen chip repaired
Most glass repair shops offer windscreen chip repair as a standard service. You can find them by searching for "windscreen repair" or "glass repair" in your area, or by asking your car insurance provider for a recommended repairer. Many insurers have partnerships with specific shops and may cover the repair cost in full or in part, depending on your policy. Some policies include windscreen cover as standard; others require you to add it as an optional extra.
Some mobile repair services will come to your home or workplace to repair the chip, which saves you a trip to a shop. Mobile repairers carry the same equipment and resins as fixed shops and can perform the repair in your driveway. This option is convenient if you have a busy schedule, though it may cost slightly more than a shop-based repair.
Before booking, call ahead and describe the chip—its size, location, and whether it has started to crack. The repairer can tell you whether the damage is repairable and give you a cost estimate. Most repairs take between 30 minutes and two hours, depending on the chip size and the resin type used.
What to expect during and after the repair
On the day of repair, the technician will inspect the chip under magnification to assess the damage and decide whether repair is feasible. If they proceed, they will clean the area, inject the resin, and allow it to cure. You will be asked to leave the car parked and undisturbed during curing—do not drive it when ready after repair, even if the surface looks dry. The resin needs the full curing time to reach full strength.
After repair, avoid car washes, heavy rain, and high-pressure water spray for at least 24 hours. These can introduce moisture into the repair before it has fully hardened. Do not explore adhesive-backed stickers or suction-cup mounts to the windscreen near the repair site for at least a week. If you need to use your windscreen wipers, do so gently and avoid pressing them hard against the repaired area.
The repaired chip will not be completely invisible—you may still see a slight mark or haze at the repair site, especially in bright sunlight or at certain angles. This is normal and does not indicate a failed repair. The glass is structurally sound even if it is not cosmetically perfect. If the repair fails and the chip spreads into a crack within the warranty period (usually 30 days to one year, depending on the shop), most repairers will replace the windscreen at no cost or at a reduced price.
Cost and insurance coverage for chip repair
Windscreen chip repair typically costs between £50 and £150, depending on the chip size, your location, and whether the repairer is mobile or shop-based. This is significantly less than windscreen replacement, which usually costs £200 to £500 or more depending on your vehicle make and model. Some insurance policies cover chip repair in full; others require you to pay a small excess (often £0 to £50) before the insurer covers the rest.
Check your insurance policy documents or contact your insurer to find out whether windscreen damage is covered and what your excess is. If you do not have windscreen cover, paying for repair out of pocket is still far cheaper than paying for replacement later. Some insurers will not cover a replacement if you ignored a repairable chip and allowed it to spread into a crack, so addressing the damage early protects both your safety and your wallet.
Why ignoring a chip leads to bigger problems
A chip left unrepaired will almost certainly spread into a crack within days or weeks. Each time you drive over a bump, brake suddenly, or experience a temperature change, the glass flexes slightly. This flexing puts stress on the edges of the chip, causing the damage to propagate outward in a spiderweb pattern. Once a crack has formed, it weakens the entire windscreen structure and can compromise your safety in a collision.
A cracked windscreen also fails the MOT test in the UK if the damage is in the driver's line of sight or is longer than 30 centimetres anywhere on the glass. This means you cannot legally drive the vehicle until the windscreen is replaced. Repairing a chip before it cracks keeps you road-legal and avoids the inconvenience and cost of an emergency replacement.
Frequently Asked Questions
Can I repair a chip myself with a DIY kit?
DIY windscreen repair kits are available online and in auto shops, but they rarely produce results as good as professional repair. The kits lack the pressure applicators and precision equipment that professionals use, making it difficult to inject resin deep into the chip. If you want to try a DIY kit, use it only as a temporary measure while you arrange professional repair. Professional repair is worth the cost.
How long does a windscreen chip repair last?
A properly done repair can last the lifetime of the windscreen if the resin has fully cured and no moisture has entered the repair. However, the repaired area is slightly weaker than undamaged glass and may fail if the windscreen is struck again in the same spot. Most repairs come with a warranty of 30 days to one year; if the repair fails within that period, the repairer will usually replace the windscreen at no cost.
Will my insurance cover the repair if a stone hit my windscreen?
Most comprehensive insurance policies cover windscreen damage, including chips and cracks, though you may have to pay an excess. Some policies cover windscreen damage with no excess at all. Check your policy documents or call your insurer to confirm your cover and excess amount before booking a repair.
Can a chip be repaired if it is at the edge of the windscreen?
Chips at the very edge of the windscreen are difficult to repair because the resin cannot bond properly to the edge of the glass. If the chip is within about 5 centimetres of the edge, most repairers will recommend replacement instead. Chips in the middle or upper areas of the windscreen are much easier to repair successfully.
What should I do if the chip spreads into a crack after repair?
If the repair fails and a crack develops within the warranty period, contact the repair shop when ready. Most shops will replace the windscreen at no cost or at a reduced price if the repair was done correctly and the failure was not caused by further impact or neglect. Keep your repair receipt and any warranty documentation the shop provided.