Are Metal Roofs Indestructible?

Simply stated, no. Metal roofs are definitely known for their durability and longevity. They have unique characteristics, however, that can still cause leaks and widespread damage. Unlike a traditional flat BUR or modified roof, metal roofs are NOT designed to be waterproof. They are designed for proper water flow, meaning there should never be any ponding or standing water on the roof for an extended period of time.

Why Do Metal Roofs Leak? 

Here are a few of the most common culprits of metal roof leaks:

  • Surface rust. Just because a metal roof is rusted, doesn’t mean it’s leaking. Left unattended, however, that rust can peel the coating and cause 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. Holes or crimping/creasing of the metal panels, most commonly caused by foot traffic, can lead to ponding water and ultimately rust and roof leaks.
  • Movement. A metal roof is designed for movement. This allows for proper waterflow off of the roof. If a repair product that doesn’t allow for proper elongation (or flexibility) is used, the panels will continue to move but the patch will not. This will cause more issues than the original roof leak.
  • Incompatible materials. In addition to elongation properties, specific materials should be used for metal roofs to avoid corrosion and rust. Dissimilar metals cause a negative reaction when situated together.
  • Punctures. Holes, creases and crimping are generally caused by foot traffic and/or by HVAC equipment installation. If heavy HVAC equipment is dragged across a metal roof, you risk a trail of damaging tears and punctures.
  • Fastener issues. There are two types of metal panel attachments – clips and fasteners with rubber washers.  Clips fasten to the purlin and the fasteners, which generally have a sealant underneath, are concealed once the metal laps on the panels are seamed or crimped together. Fasteners with rubber washers are self-drilled often every 2 square feet. Over time, these fasteners can back out and leave holes or gaps between the metal and the rubber washer where they were once installed, which opens the roof to water intrusion.
  • Open laps. If not properly installed, seams along the metal panels can lift and open the area for water . . . and ultimately structural damage.
  • Missing parts. Over time, wind, debris or even deterioration can cause pieces and parts of a metal roof to fall off. Damaged foam closures, vent flashings and boots, edge metal, gutters and downspouts can all lead to water intrusion and leaks.

Check out how this facility resolved metal roof leaks – and saved considerable costs – without a roof replacement!

Building with metal roof