How to Repair a Hole in a Metal Roof System

According to the National Association of Home Builders, asphalt shingles last about 20 years, composite shingles about 25 years, and wood shakes about 30 years. Aluminum or steel roofs, on the other hand, can easily last 50 years or more, and zinc roofs have been known to last 80 years or more. Additionally, metal roof sealant typically lasts up to 10 to 20 years. To prevent leaks, check your roof after any damage occurs to determine if holes need repairs or patches need to be resealed.

When a metal roof system is installed properly, its life expectancy is second to none. However, no building material, especially one that faces the constant weather battering of a roof, lives forever. Like all roofing systems, a metal roof requires regular maintenance and repair. Any roofing repair can be a hit-or-miss proposition. Done properly, a metal roof leak repair can last as long as the roof system itself. Done improperly, those same repairs can quickly fail, leaving the homeowner or building owner with a recurrent or constant leak.

Metal roofs commonly leak because of improperly installed screws or damaged portions of the roof that create holes. A recurring leak can be frustrating, but more serious is the interior damage and mold growth it can cause. It is always best to repair a roofing problem quickly and correctly. Thankfully, homeowners can fix a leaking hole in their metal roof themselves by cleaning, patching, and sealing the area.

Cost of Professional

Metal roof repair costs will depend on the extent of the damage and whether you can complete the labor yourself. Some repair prices are based on square footage and cost between $1 and $5 per square foot. These typically include sealing seams that are leaking, replacing or fixing fasteners, re-coating roof panels, or adding new panels. The following are common repairs and the average prices for a professional fix:

Repairing splits, cracks, or gaps:$600
Fixing leaks:$700
Rust and corrosion repair:$1,750
Fixing areas that are buckling or wrinkling: $1,750

Homeowners can repair small cracks, leaks, and rust themselves to save on labor costs. However, larger cracks or buckling and wrinkling often require replacement. In these cases, it’s best to consult a professional to ensure repairs are completed correctly for the long-term durability of your roof. Most leaks can be located in your attic by finding rafters and joists with water damage, but a professional can also help you find the source of your leak if needed.

Unique Considerations

Repairs to a metal roof 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 surrounding metal. This difference in expansion and contraction between the two products places stress on the repair, which can lead to cracking, splitting, and ultimately, failure of the patch.

Safety Considerations

Safety is a major concern when completing any roof-repair project. Most of the tools and materials you’ll need can be found at any home center or hardware store, but you may need to seek some of these items from a roofing store that carries a range of roofing materials and repair products. 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. Do not attempt on-roof repairs if you are not fully comfortable working at heights and on ladders. 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.

Clean the Repair Area

The first step in the repair of any metal roofing material will involve cleaning the surface. A hole in a metal roof system can be caused by any number of sources. Holes 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 it is most likely dirty and will require cleaning. Thoroughly clean the surface of the metal panel using Simple Green or another cleaner, until the surface of the roof panels is completely free of any dirt, film, or algae growth. Any cleaner residue will compromise the integrity of the roof repair so be sure to wipe it away with a wet cloth.

Scuff the Metal

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 later deterioration and rust.

Measure the Repair Area and Cut a Patch

Cut the chosen sheet metal to a size that matches the area to be patched. The sheet metal patch should overlap onto the metal panel at least 2 inches past the edges of the damaged area. After the sheet metal patch has been cut and fit to size, round the corners of the patch with a file or emery cloth to prevent any sharp corners from becoming a catching spot for snow or ice. Once the patch has been measured, place it over the hole being repaired. Take a pencil and outline the patch onto the roofing. Remove the patch and examine the outline to make sure the patch will overlap by at least 2 inches in all directions past the edges of the damaged area.

Install the Repair Patch

Apply a color-matched urethane 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. Press the patch into place over the damaged area. The sealant should squeeze out from the edge of the patch along all sides. If there are areas where the sealant is not oozing, these are areas where moisture may later penetrate under the patch, causing a deterioration. Apply a little more sealant there to eliminate any gaps.

Secure the Patch

Once the patch has been pressed in place, attach it to the surface of the metal roof panel, using pan-head sheet metal screws. Space the screws every 4 inches around the perimeter of the patch. The screws should be applied within 1 inch of the edges of the patch so that they apply uniform pressure to the edges and to the sealant beneath the patch. The screws should be only long enough to secure the patch to the underlying roofing panel. Never screw the patch down through the roofing panels and into the roof decking or rafters.

As necessary after the patch has been attached, retool any sealant that is bleeding from the edge of the patch, using a putty knife. This will ensure that the sealant properly seals the edges of the patch and prevents moisture from penetrating. Let the roofing sealant dry as directed by the product instructions. It may take a day or more to skin over but up to one week to cure fully.

Paint the Patch to Match the 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 edges of the patch. Paint over the surface of the patch and onto the surface of the underlying panel. It may be necessary to wait for the sealant to fully cure before it will accept paint. Also, confirm that the paint is compatible with the sealant you used.

Holes in Raised Roofing Seams

If the hole or damage to the roof is in the raised seam between panels rather than in the flat area of a panel, patch it with an asphalt-impregnated glass-membrane fabric over the damaged portion of the seam itself. On raised-seam roofs, it is important that the individual panels be allowed to move along the seams, so never attach a metal patch that is anchored to both roofing panels over the seam. Instead, repair the damage to the seam with narrow strips of membrane fabric confined to the raised seam section. The patching strip should overlap the damaged area by at least 2 inches. Over the top of the patching strip, apply a coating of urethane sealant, then another patching strip. Done correctly, both roofing panels will still be able to move independently.