The chart below compares the physical properties of metals used in roofs. It is important to distinguish the metals and their properties according to intended assembly and usage. With metals, a particular problem is their flexibility due to heat expansion. Copper is 1.4 times more flexible than iron, making it more or less the same as stainless steel, and is 70% as flexible as aluminum. In the height of summer the surface temperature of copper sheets reaches 80℃ making a difference of 90-100℃ with its winter temperatures. The heat expansion based on this temperature difference is 100 x 1.7 = 170mm. For example, a single batten seam of 100m will expand and contract by 170mm. The longest piece of copper plating is fixed at 6m and between 5-6m expansion is taken for this size variance for tiling.
According to Young's modulus, which is the standard for stretching and bending, copper comes in at 60% of lead making it a fairly soft metal. While this makes it easy to work on, it also leads to change in its shape due to expansion and contraction and external force. It is 3/4 as hard as iron and half as hard as stainless steal meaning the surface can be damaged during assembly – care must be taken during any work performed on the metal.
