Coatings are often used on metal roofs for additonal waterproofing and protection. However, as evident in the photos above, coatings can fail. Coatings can peel and crack due to impoper application, ponding water, or elemental exposure. Metal panels naturally expand and contract in response to temperature changes. Over time, this relative movement causes separation at seams and fasteners to occur. This can cause coatings to crack. If a coating is applied as a corrective measure to seams or fasteners, the relative movement will continue and cause cracking.