Galvanised steel profiled metal roofing – red rust

Cause

Erosion or scratching damage of the galvanising, exposing the steel

Repair

  • sand the corroded areas lightly to remove rust but do not use a wire brush. Prime with a zinc-rich primer, then apply at least two coats of acrylic paint
  • replace badly corroded sheets or sheets with holes. Ensure the new roofing is compatible with the existing
  • reroof when it is not economic to repair existing roofing. 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 is in contact with, or has run-off from, cedar or redwood, or timber treated with a copper-based preservative treatment 

Repair

  • sand the corroded areas lightly to remove rust but do not use a wire brush. Prime with a zinc-rich primer, then apply at least two coats of acrylic paint
  • replace badly corroded sheets or sheets with holes. Ensure the new roofing is compatible with the existing
  • reroof when it is not economic to repair existing roofing. 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 has run-off from translucent sheeting (PVC), glass, pre-painted roofing, glazed tiles, unpainted zinc/aluminium alloy-coated mild steel or aluminium 

Repair

  • sand the corroded areas lightly to remove rust but do not use a wire brush. Prime with a zinc-rich primer, then apply at least two coats of acrylic paint
  • replace badly corroded sheets or sheets with holes. Ensure the new roofing is compatible with the existing
  • reroof when it is not economic to repair existing roofing. 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

Damage to the galvanising during fixing, exposing the steel

Repair

  • sand the corroded areas lightly to remove rust but do not use a wire brush. Prime with a zinc-rich primer, then apply at least two coats of acrylic paint
  • replace badly corroded sheets or sheets with holes. Ensure the new roofing is compatible with the existing
  • reroof when it is not economic to repair existing roofing. 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

Corrosion of the steel in a corrosive environment such as near a swimming pool, or in coastal, industrial or geothermal regions 

Repair

  • sand the corroded areas lightly to remove rust but do not use a wire brush. Prime with a zinc-rich primer, then apply at least two coats of acrylic paint
  • replace badly corroded sheets or sheets with holes. Ensure the new roofing is compatible with the existing
  • reroof when it is not economic to repair existing roofing. 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

Inadequately primed end and/or side laps

Repair

  • sand the corroded areas lightly to remove rust but do not use a wire brush. Prime with a zinc-rich primer, then apply at least two coats of acrylic paint
  • replace badly corroded sheets or sheets with holes. Ensure the new roofing is compatible with the existing
  • reroof when it is not economic to repair existing roofing. 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 near the end of its serviceable life 

Repair

  • sand the corroded areas lightly to remove rust but do not use a wire brush. Prime with a zinc-rich primer, then apply at least two coats of acrylic paint
  • replace badly corroded sheets or sheets with holes. Ensure the new roofing is compatible with the existing
  • reroof when it is not economic to repair existing roofing. 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.