• In this video, This Old House general contractor Tom Silva shows how to fabricate custom-fit aluminum window flashing.

    1. Cut a piece of 8-inch-wide aluminum flashing to length using aviation snips; you could also slice through it with a sharp utility knife.
    2. Measure for the leading edge of the flashing to determine how far it'll hang down in front of the window trim.
    3. Use a metal brake or homemade bending brake to bend the leading edge of the flashing passed 90 degrees.
    4. Make a gauge block from scrap wood to represent the thickness of the window casing and trim.
    5. Slide the flashing into the brake, using the gauge block to position it at the proper depth.
    6. Bend the flashing to create the wide flange that extends up the wall.
    7. If using a homemade bending jig, set the 2x4 tapping block on top of the bent flashing and strike hit it with a hammer before removing it from the jig.
    • 10 to 20 minutes for an average-size window
    • $2 to $4 for an average-size window
    • Difficulty: Easy
      no particular skill required, especially if using a metal brake
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      Video Directory

      Selected Topic/Section

      Tools List

      • metal brake for z-flashing
        Metal brake or homemade bending jig, used to bend aluminum flashing into Z-flashing
      • framing square
        Framing square, used to mark straight lines onto the flashing
      • utility knife
        Utility knife, for scoring lines onto flashing
      • hammer
        Hammer, used to strike tapping block
      • hand clamps
        Clamps, used to hold together homemade bending jig
      • Aviation Snips
        Aviation snips, used to cut aluminum flashing to length

      Shopping List

      1. 8-inch-wide aluminum flashing, used to make Z-flashing

      2. Two beveled 2x8, used to bend flashing with homemade jig3. 2x4 tapping block, used with homemade bending jig

      4. Wood gauge block, used to represent the thickness of the window casing and trim