How To Repair A Rust Hole In A Steel Roofing Panel

Metal roofs can last for more than half a century, and correctly installed roofs generally need little maintenance. However, some metal roofs may develop small rust spots that need to be addressed before the rusted area gets larger and leaks form. In addition, a large rusted area will also require more extensive, costly repairs. Repairing small rusted areas on a metal roof is not difficult nor is it expensive, and most homeowners can perform the job themselves. Below is a list of materials and tools needed as well as a step-by-step guide to repairing rust spots on your metal roof:

Tools and materials needed

  • Fiberglass-impregnated filler designed for use with car bodies and other objects

  • Mixing board

  • Cut-off tool

  • Angle grinder with 60-grit flap-wheel

  • Aviation snips

  • 60-grit sandpaper sheet

  • Spare section of metal roof panel

  • Exterior enamel designed for use with metal

  • Roofing silicone caulk

  • Warm water and sponge or paper towels

  • Black magic marker

  • Safety glasses or goggles

  • Cotton work gloves

Step-by-step instructions

1. One of the most important steps to take when working on a roof, including your own, is to maintain a heightened level of safety awareness. Roofs can be dangerous places, and if you aren't prepared to work in the environment, there is an excellent chance for you to fall and be injured. That is why you must guard yourself by wearing proper-fitting, rubber-soled shoes to prevent slips and falls from the slippery metal. In addition, other gear is critical to protecting yourself, including eye protection and a pair of sturdy work gloves.

2. Remove area of affected roof panel - Once you have identified a rust spot, examine the surrounding area closely by feeling the paint and identifying bubbles or crumbling, flaking spots. Next, mark a line on the rooftop using permanent marker to demarcate between the rusted steel and the areas of untouched metal. Try to keep the line as straight as possible, and be cautious not to make sharp turns since you will be using a cut-off tool with a straight blade.

Once the line has been drawn on the roof, put on your eye protection and begin to slowly cut the metal panel along the lines. Be careful not to cut too quickly, or you may damage the surrounding metal pan. Carefully grab the piece you just removed and set it aside.

3. Cut and attach a sheet metal patch - After the small piece of rusted sheet metal has been removed, lay it on top of a scrap piece of metal roof and slowly trace around the edges of the piece with the marker. Next, measure across the opening at its widest and narrowest point and add 1 inch to each dimension. For example, on a cut-out piece with an 8-inch by 4-inch piece of steel, measure off a 9-inch by 5-inch section. Once you are satisfied with the appearance, size and shape, cut out the traced piece using a pair of aviation snips.

4. Attach the cut-out piece to the roofing panel - After the replacement piece has been cut out from scrap, you will need to use an angle grinder with 60-grit flap-wheel to remove the surrounding paint and debris. Run the flap-wheel so it just touches the surface of the metal and removes paint and other foreign matter. This will help establish a paint-free surface for the impregnated resin to bond to in a few moments. Wipe away any dusty sanding residue using warm water and a damp sponge or towel.

5. Attach the metal patch - Following the directions provided by the manufacturer, scoop out and mix up a small batch of the fiberglass-impregnated filler on the mixing board. Be sure to work quickly before it begins to harden.

Next, using a spreader or even an old table knife, apply mixed filler to the edge of the hole you cut in the roofing panel. Spread the filler out approximately an inch in all directions, then place some material on the edge of the patch, as well.

After the patch has been prepared, place it directly on top of the hole and line up the edges. Push out any air bubbles and search for any inconsistencies such as gaps between the two pieces of metal. Allow the filler to settle and harden—don't disturb the repair until it has had a chance to cure as directed by the manufacturer.

6. Seal and paint the repair site - The last step in the repair process is to paint the patch and surrounding area in order to disguise the repair site. Allow the paint to dry, then apply a bead of roofing-grade silicone caulk to the edge of the patch.

If you're not able to do this repair on your own, contact a company like Drey Roofing.