Code of Practice v3.0 Online
The NZ Metal Roof and Wall Cladding Code of Practice is a comprehensive design & installation guide, and a recognised related document for Acceptable Solution E2/AS1 of the NZ Building Code.
The NZ Metal Roof and Wall Cladding Code of Practice is a comprehensive design & installation guide, and a recognised related document for Acceptable Solution E2/AS1 of the NZ Building Code.
Friction cutting equipment by definition produces heat, which destroys the metallic and paint coating in the vicinity of the cut. This method of cutting is unacceptable and material cut in this manner is not covered by any warranty. See 4.15C Friction Cut Edge.
Friction blade or carborundum disc cutting is not permissible on metal roof or wall cladding.
All debris should be removed daily from the roof cladding and gutters.
At the end of each day, the work area should be cleaned by either sweeping with a softbristled broom or hosing down to remove all debris from the roof and gutters.
If the swarf staining comes from drilling, it is likely that the effect on pre-coated claddings will be aesthetic only and that the performance of the sheeting will not be greatly affected. This is not the case when hot swarf has embedded itself into the paint surface and is in contact with the metallic coating.
In weathering away by oxidation, the metallic coating will sacrifice itself to the bare steel swarf in the immediate vicinity and the life of the coating will be shortened. This situation occurs with plain AZ, ZA, and galvanised metallic coatings, where claddings are not pre-painted, and any swarf left on the surface will be detrimental to the longevity of the sheeting.
No cure will restore the surface to its original condition, but damage can be reduced by prompt action.
Mild swarf stains can be removed by sparingly applying dishwashing liquid to the immediate area, using a soft cloth. For stubborn swarf that has been left for some time and adhered to the surface, the careful use of a nylon pot cleaner may be necessary. The immediate area should be cleaned without undue pressure, as this could mar the paint surface, and the whole area should be washed down with copious amounts of water to ensure there is no remaining cleaner left on the roof.
The factory applied acrylic coating on AZ coatings can be easily damaged, and should not be scrubbed as it will cause a patchy darkening of the surface that will become evident in the repair areas.
Where extensive areas have been affected by grinding swarf, more drastic action may be required. In severe cases, the areas around the swarf should be scrubbed with a stiff bristle brush until all the swarf particles are removed. Any remaining swarf will bleed through the subsequent coating.
If the affected areas show through to the metallic coating, these should be primed first, and the total area of the visible roof cladding should be over-painted with two coats of acrylic paint. Air-drying paints weather more rapidly than factory applied coatings and quickly display colour changes, so patch painting is not a recommended option. Minor scratching or abrasions should be left alone and not be painted for the same reason.