Guide
What causes windscreen cracks, and how to prevent them
Most windscreen cracks start as a stone chip. In South East Queensland's heat and storms, that chip can turn into a crack quickly. Here's what causes it and how to slow it down.
By the Rapid Response Autoglass team · Updated
The short answer
The main causes are stones thrown up by other vehicles, sudden temperature changes on hot glass, and stress from road vibration or body flex. Keep your distance from trucks and roadworks, avoid blasting cold air onto a hot screen, and repair chips quickly before they spread.
Common causes
- Stone chips from trucks, roadworks and gravel roads — the motorways around Brisbane, Logan and the Gold Coast see plenty.
- Temperature shock — cold air-conditioning or a hose on glass that's been baking in the sun.
- Hail and storms — summer storms in South East Queensland can chip or break glass.
- Stress cracks — vibration, potholes, body flex or a poorly fitted screen.
- Slamming doors — pressure changes can spread an existing chip.
How to protect your windscreen
- Keep a bigger gap behind trucks and on gravel or roadworks.
- Park in shade or under cover where possible.
- Warm or cool the cabin gradually rather than blasting air straight onto the glass.
- Replace worn wiper blades — grit trapped under them scratches the glass.
- Cover a fresh chip with clear tape and get it repaired quickly.
How weather affects a chip
Glass expands as it heats and contracts as it cools. A chip is a weak point, so those changes concentrate stress there. A hot Queensland afternoon followed by full air-conditioning — or a cold morning followed by the demister — is a common moment for a chip to run into a crack.
Topic guide
Everything about chips and cracks
Frequently asked questions
Why did my windscreen crack on its own?
Usually an existing chip — sometimes too small to notice — spread because of heat, cold air or vibration. Occasionally a crack starts from the edge due to stress or a fitting issue.
Can I stop a chip from spreading?
Cover it with clear tape, avoid temperature extremes and have it repaired as soon as possible. Resin repair is the only reliable fix.
Can my chip be repaired, or does the windscreen need replacing?
As a rough guide, a small chip — about the size of a twenty-cent coin or smaller — that isn't on the edge of the glass or directly in the driver's line of sight can often be repaired. Long cracks, edge damage and smashed glass need a replacement. Send a photo and we'll tell you which.
Related pages
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