Repair, Retrofit, and Maintenance of Metal Panel Roof Systems
This domain tests inspection routines, correct repair methods, and the structural checks that come with retrofitting a metal roof over an existing roof.
Inspection
Twice a year and after storms: check sealant, fasteners, seams, corrosion, debris in valleys and gutters, and foot-traffic damage. Log and photograph findings. Look for backed-out fasteners and replace them with a larger diameter or a new hole with sealant, not in the old hole.
Repairs
- Sealant: remove the failed material, clean, and apply a compatible butyl or urethane. Never put silicone over butyl.
- Panels: cut out the damaged panel, install a new one, re-seam, and use a slip sheet.
- Punctures: rivet with a neoprene washer plus sealant, or a reinforced patch.
Retrofit
Metal-over-metal uses sub-framing or purlins above the old roof, thermal blocks, a slip sheet, and new panels. Verify the structure can carry the added dead load and recheck uplift at the new roof height. Do not trap moisture between old and new roofs; vent the cavity or use a vapor-permeable assembly.
Worked example
A 15-year-old standing seam roof leaks at a pipe boot. The boot is cracked, not the panel. Cut the old flange free, clean the flat pan, set a new boot in butyl tape, and fasten with stainless screws in the pan. Replacing the panel would be wasted work.
Traps
Sealing the ceiling stain instead of finding the source; reusing old fastener holes; and adding a second metal roof without a structural check.