How are closed valleys defined in roofing?

Closed valleys in roofing are characterized by roof coverings that extend over the valley without interruption. This design means that the shingles or roofing material from both adjoining slopes overlap within the valley area, creating a seamless appearance that blends the two planes of the roof. This method is commonly used as it provides a neat aesthetic and allows for proper drainage of water into the valley, reducing the risk of leaks.

The overlapping of materials also plays a critical role in managing water flow, as it helps shed water effectively down into the gutter system, preventing pooling in the valley. Closed valleys are typically preferred for architectural and aesthetic reasons, especially on residential structures where a clean line of sight and design is desired.

The other options refer to different aspects of roofing or valley designs that do not describe closed valleys specifically. While flashings may be part of an open valley system, they are not typically visible in a closed valley system. Additionally, while some materials may not require additional flashing in certain designs, the design and functionality of closed valleys focus more on the overlapping technique to achieve the desired waterproofing and aesthetic quality.