What Is an Edge Crack in a Windshield?

Why the edge is the weak point

The edge of a windshield is where the glass meets the urethane bond and the frame. That border is the weakest part of the laminate, so an impact near it — or a stress crack starting at it — tends to run inward quickly, often within hours.

Edge cracks often begin from a stone chip near the border or from no visible impact at all, as a stress crack. Either way, once a crack is at or near the edge, the surrounding glass cannot support a resin repair the way a floater can, because the border cannot restrain the fracture.

Because the edge is involved, most of these cracks call for a replacement. The full picture of why edge cracks start where they do is in our edge crack guide.

When an edge crack means replacement

The crack starts within about two inches of the border

The edge is involved, and repair is unlikely to hold.

The crack reaches the edge after growing from the middle

It has reached the weak point and will keep spreading.

No impact point is visible at the start

It is likely a stress crack, which begins at the edge and runs inward.

What to do about an edge crack

• Note how far the crack has run from the edge.
• Park in the shade and shield the glass from temperature swings.
• Keep off potholed roads and shut doors softly.
• Book a replacement promptly, since repair rarely holds.
• Skip the car wash until the glass is replaced.

More questions about edge cracks