How to Flash an Outside Corner

Step flashing is made of tin and is designed to be a water barrier on corners and crevices of structures. The most common corners that need flashing are found on roofs. The flashing should be installed with the seams on the underside of the next flashing piece to ensure that water runs over the flashing and not under it. If improperly installed with the seams exposed, water can wick into non-water resistant materials and into the structure's interior.

Roofing caulk
Galvanized roofing nails
Hammer
Tin snips
Step flashing (pre-bent to 90 degrees)

Instructions

- 1
  Hold a piece of step flashing section at the base or beginning of the corner.
- 2
  Hammer a galvanized roofing nail into the top corner on each side of the flashing. Hammer a nail into the bottom corners.
- 3
  Squeeze a line of caulk two inches below the top edge of the flashing, horizontally, across the entire piece. This will seal the seam between this piece that the next higher piece, ensuring water does not penetrate the flashing seam.
- 4
  Press the next section of step flashing above the first, with the bottom edge ½ inch below the caulk line. Hammer a nail into each top corner, followed by two nails 2½ inches above the bottom, near the edge of the flashing. Repeat this process up the corner.
- 5
  Snip away any step flashing that doesn't contact the corner.

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