Metal roofs have unique characteristics that can cause leaks and widespread damage. The difference between a metal roof and a traditional flat BUR or modified roof is that a metal roof is NOT designed to be waterproof. It is designed for water flow, meaning there should never be any ponding or standing water on the roof for an extended period of time.

So what causes metal roofs to leak? Here are some of the largest culprits.

  • Surface rust. Just because a metal roof is rusted, doesn’t mean it is leaking but left unattended, rust can peel the coating causing holes or scaling. This can lead to major structural damage. Using a rust inhibitor will not remove the rust but it will stop it from spreading.
  • Deflection. This is basically holes or crimping/creasing of the metal panels, most commonly caused by foot traffic. This can lead to ponding water and ultimately rust and roof leaks.
  • Movement. A metal roof should be designed to move, allowing for water to flow off the roof. If a repair product is used that doesn’t allow for the proper elongation (or flexibility), the panels will continue to move but the patch will not, causing more issues than the original roof leak.
  • Incompatible materials. In addition to elongation properties, specific materials should be used for metal roofs so that corrosion and rust do not occur. Dissimilar metals will cause a negative reaction when situated together.
  • Punctures. Holes, creases and crimping are generally caused by foot traffic and/or by HVAC equipment installation. Think about it – if the HVAC installer dragged the unit across a roof, there will be a trail of tears and punctures wherever that unit hit the roof.
  • Fastener issues. There are two types of attachments of the metal panel – clips and fasteners with rubber washers.  Clips fasten to the purlin and the fasteners are concealed once the metal laps on the panels are seamed or crimped together and generally have a sealant underneath. Fasteners with rubber washers are self-drilled sometimes every 2 square feet. Over time, these fasteners back out and leave holes or gaps between the metal and the rubber washer where they were once installed, opening the roof to water intrusion.
  • Open laps. If not properly installed, the seams along the metal panels can lift and open the area for water . . . and ultimately structural damage.
  • Missing parts. Over time, pieces and parts of the roof can fall off caused by wind, debris or even deterioration. Foam closures, vent flashings and boots, edge metal, gutters and downspouts can all lead to water intrusion and leaks.

With 100+ years of commercial roof experience, we’ve seen it all. If you have metal roof leaks at your facility, contact us today!

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