See one of the reasons why a metal roof leaks using tar or caulk.
Using tar or caulking to seal seams on metal roofs where two metal panels overlap is a temporary fix. The movement from the contraction and expansion of the metal will cause the tar, which hardens over time, to crack.
The added thickness of the tar or caulking on the seam, will cause water pooling and find its way into the crack. Water condensates almost every day on a metal roof and pools behind these build up tar areas and get into the cracks. This continuous water exposure causes the metal roof joint to rust and corrode.
In the video, you will see where the tar has cracked and in some areas, rust spots are showing. When rust is showing up, then there is a good chance that the metal under the tar or sealant has corroded away.
If this issue is not taken care of, it will become an expensive repair later on.
Metal roofs can last a long time provided some maintenance is performed over the years. In some cases where the fasteners are exposed, the neoprene washers corrode and must be replaced. This means removing the old screws and neoprene washers to be replaced with new ones.