Exposed fastener metal on metal roofing refers to the screws or nails that are visible on the surface, often used to hold roofing panels in place. Over time, these fasteners can lead to blistering on the metal panels, which appear as raised bubbles or spots on the roof surface. This happens primarily due to corrosion around the fastener or trapped moisture beneath the coating, which causes the metal to lift or separate from the protective layer. Blistering is often a sign that the seal around the fastener has failed, allowing water or air to penetrate, which can accelerate rust and deterioration. Simple diagnostics include visually inspecting the fasteners for rust, checking for loose or missing screws, and scanning the roof for any raised or blistered areas. You can safely do this from a ladder with caution, avoiding heavy walking on the panels, or use binoculars to inspect from the ground if the roof is steep or high.
If you notice significant rusting or blistering, it’s best to contact a professional roofer experienced with metal roofing to assess and repair the damage safely. Quick DIY fixes like replacing worn fasteners or adding sealant around exposed screws can sometimes work for minor issues but won’t address underlying corrosion or structural concerns. When consulting a contractor, ask, “How do you ensure fastener integrity to prevent future corrosion?” and “What warranty or guarantees come with your repair work, especially regarding blistering issues?” These questions help confirm that they understand the importance of proper fastener treatment and long-term protection. Proper installation and maintenance, including using corrosion-resistant fasteners and good quality sealants, are key to avoiding blistering and extending the life of your metal roof.