What Is Flashing and Why Does It Cause Roof Leaks?

Flashing acts like a waterproof collar for the vulnerable spots on your roof. It is usually made of galvanized steel, aluminum, or copper, and it sits over the joints where roofing materials meet vertical surfaces or change direction. Without flashing, rain would run straight into those gaps.

The metal pieces are shaped to shed water away from seams, sending it down the roof slope and into the gutters. Properly installed flashing follows a stepped pattern on walls and overlaps at valleys. When it works as designed, you never notice it. When it fails, water finds the tiniest opening and follows gravity into your attic or ceilings.

Look for rust streaks, dark stains, or gaps where the flashing meets the roof surface. Inside your home, watch for water spots on ceilings near exterior walls, damp attic insulation, or drips that appear during heavy rain. A musty smell in the attic can also point to hidden moisture.

Check flashing after major storms or hail. If you see shingle granules in the gutters, that is a sign of roof wear, but flashing damage may not be visible from the ground. A roof inspection from a qualified professional can spot issues you cannot see safely from a ladder.

If you notice any signs of flashing failure, act quickly. Water can travel far from the original entry point, soaking insulation, drywall, and framing. The longer it sits, the more damage it causes, including mold growth and rot.

Roof work is dangerous, and a repair done wrong can lead to bigger leaks. Local water damage pros can help with cleanup after a leak, and a roofer handles the flashing itself. If water has already reached your ceilings or walls, you need both types of help. Check your policy to see what your insurance covers.

Policies vary, and your insurer decides what is covered.