Where is Z flashing primarily installed?

Z flashing is primarily installed at horizontal seams between panel siding to help direct water away from these joints and prevent water infiltration into the wall structure. By placing the Z flashing at this location, it creates a channel that allows any water that gets behind the siding to drain out effectively, thus minimizing the risk of moisture damage, mold growth, and rot in the wall assembly.

The design of Z flashing, with a "Z" shape, enables it to extend above and below the seam, allowing for effective shedding of water while creating a barrier against moisture intrusion. This is crucial for maintaining the integrity of the building’s exterior components and ensuring long-lasting protection.

In contrast, the other choices represent areas where Z flashing is not primarily utilized or where other types of flashing may be more appropriate. For instance, while Z flashing can be involved in roofing applications, it is not typically used at the edges of roofs, over windows, or specifically at valleys where specialized flashings are designed for those purposes.