Step flashing consists of individual, L-shaped metal pieces installed at the intersection between a sloped roof and an adjacent vertical wall, with each piece overlapping the shingle course below it and being overlapped in turn by the shingle course above, creating a continuous, layered water-shedding path along the entire wall-to-roof junction.
This layered, piece-by-piece installation method is essential precisely because a single continuous piece of flashing couldn’t accommodate the roof’s slope while also properly integrating with each individual shingle course as water flows down the roof toward the wall.
Each step flashing piece typically corresponds to one shingle course, meaning a longer wall-to-roof intersection requires proportionally more individual flashing pieces, each carefully integrated with the surrounding shingles.
What Does Step Flashing Involve?
- Individual L-shaped metal pieces, one per shingle course
- Overlap with the shingle course below and above each piece
- Integration with siding or wall covering above the flashing
- Careful sequencing during installation, alternating with shingle courses
Why Is Step Flashing Important?
Because this junction combines a sloped, water-shedding roof surface with a vertical wall, step flashing’s stepped, layered design is specifically engineered to handle water flowing down the roof slope and directing it away from the wall rather than allowing it to work behind the siding or beneath the shingles at this transition. Improperly installed step flashing, whether using continuous flashing instead of individual pieces or failing to properly integrate with the wall covering above, is a common and often serious source of leaks at this location.
This detail is frequently compromised during siding replacement projects if the new siding installer doesn’t properly reinstall or integrate with the existing step flashing, which is why coordinating roofing and siding work, or at minimum ensuring the siding contractor understands proper step flashing integration, matters for long-term performance.
Step Flashing vs. Counterflashing
Step flashing addresses the sloped roof-to-wall junction along a shingled roof. Counterflashing works alongside base flashing at masonry or other rigid vertical surfaces, like chimneys, covering the top edge of base flashing to complete a watertight seal at that different type of intersection.