Rust on alloy-coated pre-finished steel roofing

Cause

Paint failure and subsequent erosion of or scratching damage to the zinc/aluminium or aluminium/zinc alloy coating, exposing the steel

Repair

  • lightly sand the corroded areas to remove rust, but do not use a wire brush. Prime with a zinc-rich primer and a metal primer; apply at least two coats of acrylic paint
  • reroof when it is not economic to repair the existing roof. 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

Roofing material is in contact with or has run-off from cedar or redwood, or timber treated with a copper-based preservative treatment 

Repair

  • lightly sand the corroded areas to remove rust, but do not use a wire brush. Prime with a zinc-rich primer and a metal primer; apply at least two coats of acrylic paint
  • reroof when it is not economic to repair the existing roof. 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

The roofing has run-off from translucent (PVC) sheeting 

Repair

  • lightly sand the corroded areas to remove rust, but do not use a wire brush. Prime with a zinc-rich primer and a metal primer; apply at least two coats of acrylic paint
  • reroof when it is not economic to repair the existing roof. 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

The roofing is near the end of its serviceable life 

Repair

  • reroof when it is not economic to repair the existing roof. 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