How to Repair Leaky Metal Roof Flashing

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  • 1-2 hours
  • Intermediate
  • 0-100
What You'll Need
Extension ladder
Roof ladder
Caulking gun/caulk
Roof cement
Roof nails
Tin snips

When it comes to keeping your roof safe from the weather elements, metal roof flashing is the key to success. Flashing is usually a thin piece of aluminum, or sheet metal, that is used on valleys, around chimneys, ventilation pipes, skylights, and along the edges. It helps to wick water away instead of sitting on exposed wooden surfaces. Through normal wear and tear, the metal roof flashing can start to leak. As a part of normal maintenance of your home, you will need to fix this leak. Fortunately, it is very easy to do with basic tools and adhesives.

Step 1 - Inspect Roof for Leaks

If you notice that there is a leak on your roof, or you suspect that there is one, take the time to visually inspect the roof. Use the combination of an extension ladder and a roof ladder to ensure your safety while walking on sloped roofs. Look at the flashing to see if it is corroded, has rust holes, or has edges that are bent up. These are the areas you will need to repair.

Step 2 - Fix Edges on Flashing

On flashing that has some of the edges bent up from branches or wind you can easily fix it without a lot of problems. Clean the surface of the roof under the flashing. Spread some roofing tar under the edge that is sticking up and bend it back down to a flat surface. Use a roofing nail to keep the section down and apply some caulking around the edge to seal against water.

Step 3 - Remove Metal Roof Flashing

For metal roof flashing that is corroded and needs to be replaced you will need to remove it from the shingles. Pry up the edges of the flashing with a small prybar carefully so you do not damage the shingles or underlying sheathing. Remove the roofing nails with the prybar as the flashing is being removed. Scrape away the excess roofing tar and caulking.

Step 4 - Cut Flashing to Fit

Using a pair of tin snips, and heavy gloves, cut the metal roof flashing to fit the area that you are repairing. The measurements do not have to be exact, but you should have enough flashing to overlap onto the shingles by 3 to 4 inches.

Step 5 - Install New Flashing

Once the flashing is cut to size, spread some roofing tar on the surface of the roof. It should be a universal thickness and evenly spread throughout the surface area. Lay the flashing onto the roof tar and press it into it. Secure the flashing with roofing nails along the edge and in the center.

Step 6 - Seal Flashing from Water

To keep the water from seeping underneath the metal roof flashing use some caulking along the edges and to cover the nail holes. You should apply a liberal amount of caulking along the edges and make sure that there are no gaps in the material.

Step 7 - Check after Rain

Once the flashing has been installed, wait for the first rainstorm and check to make sure that it is sealed adequately. If not, apply more caulking to any areas that show signs of seepage.