Step Flashing
Individual L-shaped metal pieces installed in a staggered pattern where a roof plane meets a vertical wall.
How It's Installed
Step flashing is a series of small, L-shaped metal pieces (typically 5″x7″ or larger) installed one at a time, woven into the shingle courses wherever a roof slope meets a vertical wall — a dormer, a side wall, or a chimney. Each piece overlaps the one below it like fish scales, so water is shed continuously downward onto the shingle surface rather than running behind the wall siding.
A Common Local Leak Source
Step flashing fails less often from the metal itself and more from installation shortcuts — a single continuous strip of bent metal used instead of individual stepped pieces, or step flashing that's face-nailed through the metal instead of properly integrated with each shingle course. Both defeat the overlapping design and let water track sideways into the wall cavity, often showing up as a stain on an interior wall well below where the actual leak originates on the roof.