If valley flashing cannot be seen, it is referred to as what type of valley?

When valley flashing cannot be seen, it is referred to as a closed valley. In a closed valley design, the shingles or roofing material extends into the valley, effectively covering the valley flashing. This creates a seamless look and can provide enhanced aesthetic appeal, as the flashing is concealed from view. The design helps to protect the roofing system by allowing water to flow over the flashing without being exposed, reducing the likelihood of leaks.

In contrast, an open valley design has visible flashing that is typically covered with metal. This type of valley allows for greater drainage capacity and is usually employed in areas where heavy rainfall is common. The other options, such as flat valley and circular valley, do not pertain to the standard terminology used in roofing to describe the visibility of valley flashing. Thus, closed valley is the appropriate term used in this context.