It’s what many car owners dread, that pinging sound as a stone flicks up off the road or bounces off the back of a truck and hits your windscreen.

What starts as a small chip quickly becomes a crack making its way further and further across the windscreen. So when is the right time to worry.

Dewald Ranft, Chairman of the Motor Industry Workshop Association (MIWA), a proud association of the Retail Motor Industry Organisation (RMI), says that when customers take their car in for a service, the car gets a full bumper to bumper check and this is most often the time when the workshop will pick up problematic chips and advise customers accordingly.

So, while windscreens are specifically designed to provide structural support for the vehicle as well as to stand up to the stress of travelling, damage does inevitably occur, particularly when roads are not maintained correctly. Interestingly windscreens are actually made up of two layers of glass with an inner layer of automotive safety film between them. This inner layer, or lamination, serves to hold together the broken outer layers in the event of an accident. That is why windscreens crack when struck by objects, but don’t fall apart and cave in on the driver in most circumstances.

The question is whether the damage calls for a full windscreen replacement or whether just a repair will do. Ranft says it is important to understand that your  windscreen is your protective shield. “A crack or chip compromises the efficiency of a windscreen.  Cracks can be repaired safely but there are certain rules. You shouldn't repair your windscreen if there are more than 3 cracks in totality and this includes past chips; the chip should not be too close to the edge of the windscreen and they shouldn't be in the A zone which is the area in front of the driver side,” he says.

Technology on vehicles is highly advanced and so is the windscreen which can be equipped with advanced driver’s assistance systems which help drivers prevent accidents and the seriousness of accidents. Cars with this technology will require special windscreens which needs to be recalibrated during the replacement process.

In general, however, most chips and cracks can be repaired. “Four factors are used to assess the damage – the size, type, depth, and location of the damage. This assessment needs to be done by a qualified auto glass repair technician who can then decide whether the windscreen is repairable.”

It is important to note that workshops and vehicle glass fitment centres that specialise in windscreen repairs should be able to repair chips of about 2.5cm diameter and cracks about 7cm long. Traditionally, any crack longer than that would not be repaired, and a complete replacement will be required. However, new technologies are making it possible to repair wider chips and longer cracks.”

The type of crack is also important as there are many different types of cracks, some of which can be repaired while others can’t. “In general, chips and cracks that can be covered with a R2 coin can usually be repaired,” says Ranft.

He adds that even good repairs may leave behind some discolouration, mistiness or unevenness so location of the chip or crack is an important consideration. “If the damage is in the driver’s line of sight, a repair could distract the driver. Also, any chip or crack that is at or very near the windscreen’s edge where it meets the metal frame, weakens the windscreen and compromises passenger safety. If the technician can’t see the crack or chip in its entirety, then the repair can’t be done successfully.”

Typically, an average chip or crack will take about 30 to 40 minutes to repair. A windscreen replacement can be done within a few hours. “Depending on how busy the workshop or vehicle glass fitment centre is you may need to book your car in for the day or if it is already in for a service allow for some extra time,” he explains. 

The key is dealing with a chip or crack as quickly as possible. He recommends speaking to your insurer about what is covered and what excess you may need to pay.

“Cracks lengthen before you know it. This is exacerbated by sudden changes in internal and external temperature, such as when a vehicle’s heater is switched on during cold winter periods. Another common mistake driver’s who leave their cars outside in winter make is pouring hot water over the windscreen in the morning to melt any frost. This is sure to lengthen an existing crack.  Dust also settles inside chips which can cause further damage and make repairs difficult, so the lesson is if you don’t act quickly what could have been an inexpensive repair job may turn into an expensive replacement,” he concludes.