Step flashing works by creating a layered barrier that directs water flowing down a roof away from adjacent vertical surfaces, like walls or chimneys.
Step flashing refers to a series of bent metal segments that span the joints between the shingles of a roof and adjacent walls. The unique "step-style" placement is the core of its effectiveness. Each short piece of flashing is installed underneath one shingle and over the shingle immediately below it. This creates an overlapping system.
The Mechanics of Step Flashing
Here's a breakdown of how the step flashing system operates:
- Individual Pieces: Instead of one long piece, step flashing uses many short, overlapping bent metal pieces.
- Layering: Each piece of flashing is tucked under a shingle in the course (row) it corresponds to, and then it lays over the shingle course below.
- Positioning: One side of the bent metal piece is flat and lies on the roof deck, covered partially by a shingle. The other side is bent 90 degrees and extends up the vertical wall surface, typically covered by siding or trim.
- Water Channeling: As rainwater flows down the roof slope, it encounters the top surface of a shingle. When it reaches the point where the shingle meets the wall, it flows onto the step flashing piece covering that shingle.
- Diversion: The bent shape of the flashing guides the water downwards and away from the wall structure. Because the flashing is layered over the shingle below, the water flows off the flashing and onto the next shingle down, which in turn directs it onto the next flashing piece, and so on.
- Preventing Migration: The step-style placement prevents water from migrating into the walls as it flows down the roof. The overlaps ensure that water is always directed onto a lower layer, away from the vulnerable joint between the roof and the wall.
Essentially, step flashing creates a shingle-like defense system at the wall junction, using metal pieces to shed water downwards and away from the structure, preventing leaks and water damage.
Key Benefits of Step Flashing
- Effective Water Diversion: Channels water away from wall structures efficiently.
- Prevents Leaks: Protects vulnerable roof-to-wall transitions from water infiltration.
- Durable: Typically made from long-lasting materials like aluminum, copper, or galvanized steel.
- Adaptable: Can be used with various roofing materials, including asphalt shingles, wood shakes, and tiles.
Step flashing is a crucial component in roof construction wherever a roof meets a vertical surface, providing a vital layer of protection against water damage.
