How Do Step Flashing Failures Cause Roof Leaks?

Step flashing consists of individual L-shaped metal pieces, usually made of galvanized steel or aluminum. Roofers install one piece for each shingle course where the roof meets a vertical surface like a wall or chimney. It is layered under the shingles and over or into the siding. This overlapping design is meant to direct water down and over the shingles, away from the wall. The correct installation sequence is critical for creating a watertight barrier that lasts for decades. Proper flashing channels rainwater safely off the roof surface.

When flashing fails, water follows the path of least resistance. Instead of flowing over the shingles, it runs behind them. The water then travels behind the siding or brick veneer on the wall. From there, it can seep into the wooden sheathing and framing of your home. This infiltration often happens slowly, leading to damage long before you see a stain on your ceiling. The water can travel several feet horizontally within a wall before it becomes visible, making the leak's source hard to pinpoint. This hidden path is why these leaks are so damaging.

If you suspect a flashing failure, contain interior water damage immediately. Move belongings and place buckets to catch drips. Document the damage with photos for your insurance records, as policies vary and your insurer decides what is covered. Then, contact a qualified roofer to inspect and repair the flashing. For the water damage inside, local water damage pros can properly dry the structure to prevent mold. They use industrial equipment to remove moisture from wood, drywall, and insulation that you cannot effectively dry on your own.