How To Install Metal Window Flashing

Installing metal window flashing is a key preventative measure to keep your house and windows water tight. Installed over the felt and house wrap on the top, bottom and sides of the window, it redirects water away from the window and window framing, preventing moisture buildup, rot and damage to the surrounding materials and insulation. Metal window flashing is thin and flexible and comes in two forms: sheets or tiles made of galvanized steel, zinc, aluminum or copper and metal flashing tape that has an adhesive already applied to its back for easy installation.

Things You'll Need

• Metal window flashing tiles or sheets
• Tin snips, metal hand saw or box cutter
• Measuring tape
• Silicone caulking and caulking gun
• Heavy gloves for cutting and working with sharp metal
• Aluminum nails
• Hammer

Instructions

1. Install a single piece of metal flashing along the underside of the window opening and extending it out past each corner by at least 7 inches on either side of the window. Secure the flashing with a few nails along the top and upper corners of the flashing only. If your particular window installation specifications calls for caulking, lay a bead along the top, bottom and sides now of the window now.

2. Place the window in the opening and check it for plumb and level. Hammer in a few nails along the top nailing flange only to keep the window in place during the top and side flashing installation.

3. Install a piece of metal flashing wider than the window by at least 7 inches, placing it behind the window flange on each corner but allowing it to lay over the window flange all along the window in a weaving under-over-under pattern. Place a few nails along the top of the flashing to hold it secure.

4. Nail in the side window flanges to permanently set the window, taking care not to place any nails where the side window flange and the bottom edge of the metal window flashing overlap.

5. Measure the installed window and identify the side flashing length requirements adding 7 inches on each end. Make a notch into the top end of the flashing to accommodate the thickness and depth of the top flashing piece. Slide the side metal flashing on top of the window flange abutting the side window frame and tucking under the top flashing piece and over the bottom flashing piece. Secure with a few aluminum nails along each side without nailing into the top and bottom flashing panels where the the sides, top and bottom flashing pieces overlap.

Resources

• Metal flashing tutorial