What Is the Windscreen Made Of?
Your car's windscreen is a laminated safety glass sandwich: two layers of glass bonded to a clear PVB (polyvinyl butyral) plastic film. This construction means that when struck, the glass cracks but does not shatter into shards — the plastic layer holds the fragments together.
The windscreen is also a structural component of the vehicle. On modern cars, it contributes to roof crush resistance in a rollover accident and forms part of the mounting surface for airbag deployment (the windscreen must stay in place for the passenger airbag to function correctly).
Types of Windscreen Damage
Chips
A small impact that removes a fragment of glass from the outer surface, typically from a stone thrown up by the vehicle ahead. Chips vary in shape:
- Bullseye — circular, with a dark central void
- Star break — cracks radiating outward from a central impact
- Combination break — mix of bullseye and star break
Cracks
A crack is a linear fracture in the glass that extends beyond the initial impact point. Cracks can originate from a chip left untreated (temperature changes cause chips to crack), from a severe impact, or from stress in the glass due to poor installation.
Cracks grow — especially in NZ's temperature swings (hot summer car interior, cold winter morning air on the glass), and every time you drive over a pothole or rough road.
When Can a Windscreen Be Repaired vs Replaced?
Repair (resin injection) is viable for:
- Chips up to approximately 10–15 mm in diameter
- Cracks up to approximately 30–40 mm long
- Damage that is not in the driver's direct line of vision
- Damage where the inner glass layer is not broken
Replacement is required if:
- The crack extends more than 50–75 mm (any direction)
- The chip or crack is within the driver's direct line of sight — the area swept by the wipers directly in front of the driver
- The damage has penetrated through to the inner glass layer (you can feel it with your fingernail)
- There are multiple chips or cracks, regardless of size
Repair is fast (30–60 minutes) and cheap ($80–$150). The repair fills the chip with resin to prevent cracking and restore strength — it will remain visible as a minor blemish, but stops further deterioration.
NZTA WoF Rules for Windscreens
NZTA's WoF inspection assesses the windscreen for:
- Cracks or damage in the driver's line of vision (the area approximately 300 mm either side of the driver's centreline, within the wiper-swept zone) — even small cracks here are a fail
- Cracks longer than 75 mm anywhere in the windscreen
- Multiple chips or cracks that distort vision even if individually small
- Damage that compromises the structural integrity of the glass
A windscreen with a single small chip well outside the driver's line of sight may pass a WoF inspection, but it is always better to repair promptly — chips become cracks quickly on NZ roads.
Insurance and Windscreen Cover
Many NZ comprehensive car insurance policies include windscreen cover with no excess or a reduced excess. Check your policy before paying out of pocket — a windscreen replacement that costs $400–$800 may be fully covered. Some insurers have preferred glass repair networks.
Repair is almost always free under insurance — there is no financial reason to delay a repair and let a chip turn into a crack.
Recalibrating ADAS After Windscreen Replacement
Modern cars fitted with Advanced Driver Assistance Systems (ADAS) — such as lane departure warning, automatic emergency braking, and adaptive cruise control — may have cameras or sensors mounted to the windscreen. Replacing the windscreen on these vehicles requires ADAS recalibration afterward, using specialist equipment.
Common NZ vehicles requiring recalibration after windscreen replacement: late-model Subaru Outback/Forester (EyeSight cameras), Toyota RAV4, Honda CR-V, Mazda CX-5.
Do not skip recalibration — an uncalibrated camera can cause the lane keeping or emergency braking system to activate incorrectly.
How Much Does a Windscreen Replacement Cost in NZ?
| Vehicle | Estimated NZD Cost |
|---|---|
| Standard passenger car (no ADAS) | $350–$600 |
| SUV/wagon with ADAS cameras | $600–$1,200 (including recalibration) |
| Chip repair | $80–$150 |
Prices vary by glass brand (aftermarket vs OEM), vehicle make, and whether ADAS recalibration is required. Get at least two quotes from specialist auto glass businesses.
When to Act
- Immediately repair a chip — do not wait. A chip left in NZ's varied temperatures (a hot parked car, a cold morning drive) will typically crack within days to weeks
- Book replacement promptly if you already have a crack in your line of vision — driving with compromised forward visibility is dangerous and illegal
- Before your WoF — address any windscreen damage in advance to avoid a fail and re-inspection fee