Galvanised steel profiled metal roofing – red rust
Listed under: metal, steel, Roof, cladding, durability, corrosion, rust, roof cladding, profiled metal
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.