What is the main purpose of valley flashing in roofing?

Valley flashing plays a crucial role in roofing systems, primarily serving to provide weather protection at the junctions where two sloped roofing planes meet, forming a valley. Rainwater and melting snow typically flow into these valleys, making them susceptible to leaks and moisture intrusion if not properly protected. The flashing acts as a barrier, directing water away from the roof structure and into the gutters, thereby preventing potential water damage to the roofing materials and the underlying structure.

While insulation, drainage, and structural support are important aspects of roofing and construction, they are not the primary functions of valley flashing. Insulation is meant to regulate temperature, drainage pertains to the overall management of water flow across the roof, and structural support relates to the integrity of the roof framing. In the context of valley flashing, the essential function is its ability to respond to weather conditions by safeguarding the roof from water infiltration.