How to Maintain and Repair a Metal Roof

Published April 12, 2017 by Whirlwind Team

repair metal roof

Can you repair your metal roof? The quick answer is, “Yes. Yes, you can.”

In fact, it may be simpler to repair a metal roof than a wood frame and shingle or asphalt roof. This is a good thing because a leaking roof can cause damage throughout your building if not found and fixed quickly.

Finding and repairing leaks early prevents permanent or extensive damage to wall, woodwork, floors, insulation doors, and windows.

To make things a bit more complicated, water from a roof leak doesn’t always appear near the leak. It may run through the trusses or rafters to another part of the ceiling. It can seep into the side walls or pool in a moisture barrier before spilling over.

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Causes of leaks in steel roofs

Before looking for the cause of a leak, make sure you are not dealing, instead, with heavy condensation. Check pipes from the water heater or the ductwork from the air conditioner for moisture.

Roof leaks are caused by two general problems. 

  1. Poor installation, inlcuding:
    • Omission or misplacement of the required caulking sealants and bar in longitudinal roof seam cavities
    • Failure to install an extra sealant strip at four-way panel laps and eave connections
    • Failure to install tape sealant under screw holes
    • Failure to caulk between extra trim and the underside of roof panels
    • Improperly installed flashing, roof penetrations, or joint sealants
  2. Damage from weather or aging: Separated seams, rusted areas with damaged or weathered coating, sealant failure around a fastener, and ice dams.

Inspecting the roof

There are several places to closely monitor as you perform a routine inspection or are trying to track down the source of a roof leak.

Take a careful look around the end and side laps, penetrations, transitions, J-rails, and seams and sealant. 

Pay special attention to any rusted or worn areas and any existing “rumble buttons,” metal washers paired with neoprene washers. When the neoprene washer weathers it breaks down and is prone to leaking.

Routine maintenance and recoating

You should inspect your steel roof annually. Old coating becomes weathered and scratched over time potentially causing a leaky roof.

When it’s time to recoat your metal roof, clean the roof of all dirt and loose coating. Remove any surface rust and make any needed repairs before painting the new coating.

To remove rust and dirt you can sand, grind, use a wire brush, or use a high pressure washer. 

New coating can improve emissivity and reflectance for improved energy efficiency.

Repairing your metal roof

  • Minor rust removal: Minor rust can be removed by sanding, grinding, or scrubbing the area with a wire brush. Then you can apply an approved primer or rust inhibitor over the entire area and recoat.
  • Replacing corroded or missing fasteners: As you inspect your roof, look for heavily corroded or missing fasteners. All should be replaced with a new butyl rubber washer then covered with caulk with the appropriate sealant. Once the sealant is dry and set, it should be covered with roof coating.
  • Patch holes: If you have one or two holes without wide-spread damage, you can patch the holes with a few materials and a little labor.
    • Clean the surrounding area so it is free of dirt and debris.
    • Scrape off any loose or flaking roof coating with a putty knife.
    • Apply one or two inch strips of butyl tape around the perimeter of the patch area.
    • Cut a patch out of galvanized metal to a size that overlaps the hole by two to three inches on all sides. Alternatively, you can use a layer of metal fiber membrane over the opening using even applications of adhesive underneath and over the top.
    • Pre-drill holes through the patch and roof material and insert screws.
    • Screws must go through the patch, butyl tape, and existing roof material and should tighten snugly against the roof panel. DO NOT screw into rafters or trusses.
    • Place screws every two inches and make sure the patch is flush with the roof. If not, use screws every inch.
    • Seal around the edge of the patch and screws with caulk and allow it to dry. Cover with roof coating.
  • Membrane a seam: If you have a small, narrow hole, you can repair it with a membrane. Clean the area of the repair as before, then coat the area with high-quality, aluminum-based roof coating.

    Make sure to cover both sides of the seam but do not allow the coating to completely solidify. Cover the hole or split with an asphalt-impregnated glass-membrane fabric. Lay it across the seam on top of the roof coating. Make sure it is wider than the seam and overlaps it by at least two inches on all sides.

    Coat the roof again to place a second coat over the membrane.
  • Replace an entire section: Extensive damage to one or more roof panels may require replacing the sections. As you do so, carefully inspect the underlying rafters and area under the roof for any additional damage.

    Check the overlay for structural damage and replace wet insulation. Allow the attic area to completely dry before replacing the section.

    Do not screw the roof to the rafters. A galvanized metal roof is fastened only around the perimeter to allow the panels to expand and contract with the changing temperature. Do not add any rumble buttons.

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Steps for replacing a roof section

  1. Loosen the J-rail by removing the screws on both sides of the roof where you will overlay new material. You do not need to completely remove the J-rail, only loosen it so the old section can be slipped out; the new one slides underneath.
  2. Examine the interior of the roof with a flashlight to locate and repair damaged insulation and remove standing water.
  3. Replace damaged rafters and allow the attic to dry before replacing the overlay. You can use tin snips to cut away the damaged edges if you need to access the attic, otherwise there is no need.
  4. Cut the new sheet making sure it is the same length as the damaged section and at least a foot wider on both sides.
  5. Apply butyl tape along the bottom edges of the new sheet of metal and place it over the damaged section.
  6. Slide the end under the J-rail at both ends and insert screws long enough to go through the J-rail, butyl tape, new roof metal, and the side of the house.
  7. Attach the sides by inserting screws through the new metal section, butyl tape and existing roof materials until the metal is flush.
  8. Seal the edges on all four sides and the seams with metal roof coating.

Metal roofs last for decades; many are warrantied for 30 years or more. However, holes sometimes happen. Sealants wear out and screws disappear. Find the source of the leak quickly and repair it to minimize further damage of your building.

Metal Roofing Guide

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