Bottom corner of copper flat roof panel that went un-soldered. Notice the vertical seam. Only the right side of the joint has solder. Same with the left horizontal seam. This shows that the soldering iron was kept to that side of the seam and that little heat was applied to the left, or actual folded seam area, and little solder was able to flow into the joint.

Broken soldered flat roof seams like this are usually caused by poor joint preparation or soldering too fast and not allowing the solder to flow into the seam.

Bringing four panels together is poor practice. This whole roof was done that way instead of staggering the copper roof panel joints. The buildup of sheet metal layers caused undue stress on a joint that is mechanically unsound.

Holes in the soldered seam such as these are caused when the roofer stops the heat on a seam prematurely. The solder has not sweated thoroughly through the seam and the residual flux and impurities have bubbled out of the seam unnoticed.