In roofing terminology, what does an "open valley" mean?

The term "open valley" refers specifically to a roofing design where the valley area is left exposed rather than covered with shingles. In an open valley, the materials used on adjacent slopes are directed into the valley, which is typically lined with a waterproof barrier, allowing water runoff to flow freely without obstruction. This design can enhance water drainage and is often made with metal flashing to provide durability against weather elements.

This differentiation is crucial for understanding roofing systems, as it impacts both the functionality and aesthetics of the roof. Open valleys not only help prevent water accumulation but also create a clean visual line on the roof, distinguishing them from other valley constructions where shingles might overlap and cover the line, leading to potential water retention and wear over time.