Profiled metal roofing – corrosion at lapped ends
Corrosion at lapped ends of galvanised steel roofing sheets
Causes
The underside (back surface) of the edges of sheets have not been primed and do not get cleaned
Listed under: finishes, metal, steel, paint, Roof, cladding, framing, durability, corrosion, rust, roof cladding, profiled metal
Cause
The underside (back surface) of the edges of sheets have not been primed and do not get cleaned
Repair
- cut damaged roofing back to the next purlin; install short lengths of roofing, sealed to and lapping under the existing roofing by 150 mm
- reroof when not economic to repair existing – by the time corrosion is visible, damage is usually severe and is likely to require replacement. If the old profiled metal roof has met minimum Building Code durability provisions (it has lasted at least 15 years) a building consent is not required; if not, a consent must be obtained before reroofing.
Cause
Water trapped in end laps
Repair
- cut damaged roofing back to the next purlin; install short lengths of roofing, sealed to and lapping under the existing roofing by 150 mm
- reroof when not economic to repair existing – by the time corrosion is visible, damage is usually severe and is likely to require replacement. If the old profiled metal roof has met minimum Building Code durability provisions (it has lasted at least 15 years) a building consent is not required; if not, a consent must be obtained before reroofing.