Will a cracked windscreen fail the NCT?

Updated 3 November 2026 · 4 min read

Windscreen damage is one of the easier NCT problems to avoid, because you can see it long before the test. Whether a chip or crack fails depends mostly on where it is and whether it affects your view of the road, not simply on whether the glass is damaged.

The National Car Test checks that a car meets minimum roadworthiness standards, and a clear view of the road is one of the most basic of those. The test covers the windscreen itself, the wipers and washers, and anything that obstructs the driver's view. Here is how each area is approached, and what you can do in the weeks before your appointment.

How windscreen damage is judged

Ireland's vehicle testing follows the EU roadworthiness framework (Directive 2014/45/EU), which treats damage to the windscreen according to where it is and how much it affects the driver's view. In practice, testers look at:

• The area in front of the driver. Damage in the part of the screen the driver looks through when driving, the zone swept by the driver's wiper and especially the central band in line with the steering wheel, is treated most strictly. Even a fairly small chip here can be a problem if it distorts the view.
• The rest of the swept area. Larger damage may be tolerated away from the driver's central view, but long cracks running across the swept area are likely to be treated as a defect.
• Cracks that weaken the screen. A crack running from edge to edge, or one that makes the screen insecure, is a serious defect regardless of exactly where it sits.

For comparison, the UK MOT publishes specific figures: damage over 10mm in a 290mm-wide zone centred on the steering wheel, or over 40mm elsewhere in the swept area, is a failure there. Those numbers are not the NCT's own rules, but they give a sense of how small damage needs to be to pass in the most sensitive part of the screen.

Will a chip fail the NCT?

A small chip outside the driver's direct line of sight will often not fail on its own. A chip right in front of the driver is a risk. The simplest answer is that a repaired chip is much less likely to cause a problem than an open one, and a repair is usually quick and often covered by insurance. Read our guide to repairable windscreen cracks to see whether yours is suitable.

Will a cracked windscreen fail?

A long crack in the swept area, or one in the driver's view, is likely to fail. Cracks also tend to grow, so a crack that is borderline when you book may be well past it by the test date. If the screen is cracked, plan for a replacement before the test, and allow time for any camera calibration the car needs afterwards.

Wipers and washers

Wipers and washers are a common, avoidable reason for failure. The NCT's own pre-test advice lists wipers that are missing, do not clear the screen effectively or leave too small an area clear. Before the test:

• Check the blades for splits, hardened rubber and smearing. Replace them if they judder or leave streaks.
• Make sure both wipers park correctly and work on every speed setting, including intermittent.
• Fill the washer bottle and check that the jets hit the screen rather than the roof or bonnet. A pin can clear a blocked jet.
• If the car has a rear wiper and washer, check those too.

Stickers, mounts and other obstructions

Anything that blocks the driver's view can be an issue. Large stickers, phone mounts or sat-nav holders in the swept area, and dangling objects from the mirror, are best removed before the test. The discs you are required to display should be in the normal position, away from the driver's main field of view.

Tinted windows

The NCT measures how much light passes through the windscreen and front side windows. Aftermarket tint film on the front glass is a frequent problem. If your car has added tint, check the current permitted levels on the RSA website before the test.

What happens if your car fails on the windscreen

You get a report listing the defects. Once the screen has been repaired or replaced, the car goes back for a re-test. Whether that re-test is a visual check or a full test, and the time allowed, is set out on your fail report and on ncts.ie. Keep the invoice for the repair work in case you are asked about it.

A quick pre-NCT windscreen check

1. Clean the screen inside and out so you can see every mark. Our guide to cleaning the inside of a windscreen helps here.
2. Sit in the driver's seat and look for chips and cracks in front of you and in the wiped area.
3. Get small chips repaired early. Plan a replacement for cracks.
4. Test the wipers and washers on every setting.
5. Remove anything stuck to or hanging in front of the screen that you do not need.