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.
Washing may be carried out with a hose and a soft bristle brush, using fresh water. In areas where heavy industrial deposits dull the surface, a thorough cleaning can be ensured by using a 10% solution of household detergent and fresh water followed by a thorough rinse with clean water.
Stronger concentrations of cleaners than those recommended can damage coating surfaces, and organic solvents and abrasive cleaners should not be used. When cleaning coated surfaces, tar and similar substances may be removed with mineral turpentine, but the surfaces should then be washed thoroughly with detergent and water.
Always clean coated surfaces from top to bottom, and rinse immediately and thoroughly with fresh, clean water avoiding over-cleaning or scrubbing, which can damage painted surfaces.
The scrubbing of bare AZ coated steel cladding can remove the thin factory applied clear acrylic film and should be avoided for this reason.