What Is Flashing and Why Does It Cause Most Roof Leaks?

Flashing is the metal barrier that seals the vulnerable spots on your roof where water could sneak in. You'll find it at valleys, where two slopes meet, around chimneys, skylights, vents, and along the edges where the roof meets a wall. Its job is to direct rainwater away from these joints and keep it flowing down the shingles.

Most flashing is made of galvanized steel, aluminum, or copper. Over time, it can corrode, loosen, or develop tiny gaps. When that happens, water finds its way underneath and starts leaking into your attic or ceiling. That's why flashing problems are a leading cause of roof leaks, even when the rest of the roof looks fine.

Look for water stains on ceilings or walls, especially near exterior walls or chimneys. A musty smell in the attic or visible daylight around roof penetrations are also red flags. You might notice peeling paint or damp spots on interior walls, which often trace back to flashing issues.

Outside, inspect the flashing for rust, bent edges, or missing sealant. If you see shingles that are lifted or cracked near the flashing, that's another clue. Catching these signs early means less water damage and a simpler repair.

• Water stains on ceilings or walls
• Musty odor in the attic
• Visible gaps or rust on flashing
• Lifted or damaged shingles near flashing
• Peeling paint or damp drywall
• Dripping sounds during rain

Regular maintenance is your sensible defense. Have a roofer inspect your flashing at least once a year and after any major storm. Keep gutters clean so water flows freely, and trim overhanging branches that could damage the roof.

When you replace your roof, make sure the flashing is replaced too. Old flashing under new shingles is a recipe for future leaks. If you notice any issues, address them promptly to avoid bigger problems down the road.