What is the minimum required width for the bottom layer of valley lining material in open valleys?

The minimum required width for the bottom layer of valley lining material in open valleys is 18 inches. This specification is critical in roofing design and construction, as it ensures proper water drainage and prevents leaks in the valley area, which is one of the most vulnerable points on the roof.

The 18-inch width provides enough coverage to effectively channel water off the roof and into the gutters, reducing the risk of water pooling and potential damage. This width is also in compliance with industry standards to ensure durability and performance in various weather conditions. Adhering to this requirement is essential for maintaining the integrity of the roofing system and ensuring that it functions properly over time.

In contrast, options suggesting wider materials may not align with the minimum specifications set forth in roofing guidelines, which are designed for effectiveness and efficiency while balancing material use.