Metal roofing materials expand and contract due to variations in temperature. As a result, panels will have a level of oil canning to some degree; this will be more visible at certain times of the day, when light and shadow fall off the panel surface.
Oil canning is part of the aesthetic of all metal roofing materials and we reference this in our documentation.
For more information and an example of this, here is some information from VMZinc on Transversal Junctions / Expansion.
The temperature to bear in mind in Sydney, is from 0°C (mid-winter) to +90°C in the sun (height of summer) on the metal's surface. During installation, if we assume an ambient temperature of 25°C, we must also factor in an additional 65°C (expansion) 25°C less (contraction).
For a 10 metre long panel:
A. anticipate an 0.022 mm x 10 x 65 = 14.30 mm increase in length,
B. anticipate 0.022 mm x 10 x 25 = 5.5 mm contraction
VMZinc also has the following information on its website for VMZinc Maintenance, storage recommendations, ventilation, and more. This is also in our documentation.
Please inform us before your project commences if you would like to discuss this further.