Repairing a Hole in a Metal Roof System

Man building a roof

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When properly installed, a metal roof system's life expectancy is second to none. But like all roof systems, they require regular maintenance and repair. Repairing a roof can be a hit or miss proposition. Done properly, repairs can outlive the roof system itself. Done improperly, those same repairs can continue to break and fail, leaving the homeowner or building owner with a continual leak condition. A recurring leak condition can be a source of aggravation, but it also can lead to interior building damage and potential mold growth. It is always best to fix the problem right the first time to ensure your solution provides a watertight roof system for a long time.

Repairs to the surface of a metal roof system can be particularly difficult. Metal roofing repairs are prone to premature failure because the patched area may have a different rate of expansion and contraction than the existing metal roofing panels. This difference in expansion and contraction between the two products places stress on the repair and leads to cracking, splitting and ultimately failure of the patch.

The following is a recommended process for repairing a hole in a metal roof system.

Tools and Materials You Will Need

  • Metal snips
  • Cordless drill
  • Wire brush
  • Caulk gun
  • Paintbrush
  • Pencil
  • Sheet metal--ensure that the type of sheet metal matches the type of metal used in the roof.
  • Urethane sealant--matched as closely as the color of the metal panel being repaired.
  • Pan-head sheet metal screws
  • Paint-- color-matched to the metal panel being repaired.
  • Simple Green or another cleaner--choose a cleaner does not leave a residue.

Step One: Clean the Repair Area

A hole in a metal roof system can be caused by any number of sources. The hole may be from deterioration and rust, or it may be from something falling onto the roof surface, such as a large branch. No matter what the cause of the hole, the area around the hole is most likely dirty and will require cleaning.

Clean the surface of the metal panel using Simple Green or another cleaner. Clean the surface of the roof panels until any dirt, film or algae growth is completely removed. Any residue will compromise the integrity of the roof repair. After cleaning the surface of the metal panel, use a wire brush to scuff the surface where the repair will be made. Scuffing the surface will help the sealant bond to the metal. Use the wire brush only in the area to be patched; wire brushing beyond that may remove the protective coating from the metal panel surface, causing deterioration of the panels.

Step Two: Measure the Repair Area and Cut a Patch

Cut the sheet metal to a size that matches the area to be patched. The sheet metal patch should overlap onto the metal panel at least two inches past the leading edge of the damaged area. After the sheet metal patch has been cut and fit to size, round the corners of the patch to prevent any sharp corners from becoming a catch for snow or ice.

Once the patch has been measured, place it over the hole being repaired. Take your pencil and outline the patch. Remove the patch and ensure that there it will overlap by at least two inches in all directions past the leading edges of the hole.

Step Three: Install the Repair Patch

Apply the sealant to the surface of the metal panel being repaired, staying just inside the marked pencil line. Apply the sealant liberally in the area, so that there are no gaps or voids at the leading edge of the patch.

Take the patch and press it into place. The sealant should squeeze out from the leading edge of the patch along all sides. If there are areas where the sealant is not oozing from the edge, these are areas where moisture can penetrate under the patch causing a deterioration of the patch. Apply a little more sealant here to eliminate gaps. 

Step Four: Secure the Patch

Once the patch has been pressed in place, attach the patch to the surface of the metal roof panel, using pan-head sheet metal screws. Space the screws every three to four inches around the perimeter of the patch. The screws should be applied within one inch of the leading edge of the patch so that they apply uniform pressure to the leading edge of the patch and to the sealant beneath the patch.

As necessary after the patch has been attached, retool the sealant that is bleeding from the edge of the patch. This will ensure that the sealant properly seals the leading edge of the patch and prevents moisture from penetrating.

Step Five: Paint the Patch to Match Roof

If desired, the surface of the patch can be painted to match the color of the metal roof panels. To do this, lightly wire brush the surface of the metal patch and the metal panel just past the leading edge of the patch. Apply the paint to the surface of the patch and onto the surface of the underlying panel. It may be necessary to wait for the sealant to cure before it will accept paint. Also, confirm that the paint is compatible with the sealant you used.

Final Note

Safety is a major concern when completing any roof repair project. A hole in a roof system may indicate that there are other concerns about the overall structure, including decking deterioration. Be sure to conduct a proper under-deck safety review and roof analysis before attempting to complete this or any roof repair. If there are concerns about completing your roof repair safely, contact a professional roofing contractor, who can complete the repair for you in a safe and professional manner.