Most people who drive have likely had the same or similar experience of driving along on the highway, being startled by the impact of a rock hitting the windshield, and then noticing a large crack left as a result. If and when this happens to you, your first thought (after being relieved your windshield did its job in protecting you, of course) is whether or not such a crack can be repaired. The answer to that question can depend on a number of different factors.
First, however, it helps to understand the design of your windshield and how it is able to stay together even after being struck by road debris. Your windshield is actually three layers of glass: two durable outer layers and an inner safety layer known as lamination. The lamination holds the outer layers together and allows the windshield to crack rather than shatter when impacted.
One of the primary factors influencing whether your windshield needs to be repaired or replaced is the length of the crack. Typically, a crack less than three inches long (or the length of the short side of a dollar bill) can be repaired by injecting the outer layer with a clear, curable resin. However, longer cracks increase the risk of the inner lamination becoming exposed, thus compromising the structural integrity of the windshield. If a crack is longer than three inches, you typically will have to have the windshield replaced.
Crack Location or Depth
There are other factors that can determine whether you need windshield repair or replacement as well. Cracks that occur along the edge of the windshield can weaken the adhesive force of the entire unit. Others that occur in your line of sight will reduce your visibility even after attempts have been made to repair them. A crack on the inside of the windshield will be difficult to repair. In other cases, the location of the crack is not so much of an issue as its depth is. Most cracks only penetrate the hard outer layer. However, cracks whose impact reaches the inner laminate layer or that go completely through the windshield are beyond repair.
Prevention of Further Damage
Don’t put off having it examined – continuing to drive with a crack or chip may allow dirt and other debris to get inside the inner laminate layer and further damage the windshield. Wind pressure infiltrating the crack as you drive can also cause it to spread. Acting quickly could mean the difference between a quick repair job and a windshield replacement.