Metal roofing, particularly wide, flat panels like those found in standing seam systems, is susceptible to an aesthetic wave or buckle known as "oil canning" due to minor inconsistencies during the manufacturing, installation, or thermal stress. While oil canning is generally not a structural flaw, it can be an aesthetic concern. A knowledgeable contractor will discuss this phenomenon... https://kkroofspecialist.com.sg/metal-roofing-contractor-singapore/