A roof's wind resistance depends primarily on the continuity of the entire load-transfer system, not on sheet thickness alone. The building owner or user should check whether the design and installation documentation account for the location, height and surroundings of the property, and whether the fixings and edge details match those assumptions. When assessing an existing roof, it is worth looking for signs of earlier alterations, corrosion and loose components. The scope of any inspection is best based on the individual conditions of the building, not on a pattern copied from a neighbouring property.

Before commissioning cleaning or repair, establish whether the corrosion mark comes from the coating, a metal filing or a fixing. An owner can assess critical points from the ground, paying attention to gutters, the chimney, the eaves and places where leaves collect. Also check the condition of the package on delivery and how sheets are stored and cut, because corrosion can begin before installation. The type and parameters of the coatings affect durability, so leave material selection to the designer, and colour alone does not determine how the sheet will behave in a demanding environment.