What is the minimum width for a clay and concrete roof tile valley flashing underlayment when the slope is 3 units vertical in 12 units horizontal or more?

The minimum width for a clay and concrete roof tile valley flashing underlayment when the slope is 3 units vertical in 12 units horizontal (which translates to a 25% slope) or more is 24 inches. This requirement is established to ensure proper water management and to prevent moisture intrusion in roof areas that are subjected to runoff.

Valleys on a roof are critical points where water flows converge, and thus, the underlayment must be sufficient in width to adequately cover the area and provide a reliable barrier against water infiltration. A minimum width of 24 inches allows for adequate overlap and coverage, even in adverse weather conditions, ensuring that the flashing is effective in directing water off the roof and into the gutter system.

This standard promotes durability and helps reduce potential leaks beneath the roof coverings, making it essential for long-term performance. The requirement reflects industry best practices and is often detailed in building codes and roofing manufacturer guidelines to enhance the reliability of the roofing system in various climates.