What is the function of the base flashing in a flashing system?

The function of base flashing in a flashing system is crucial for protecting the structure from water intrusion, particularly around areas where the roof meets vertical surfaces. Base flashing is specifically designed to direct water away from the building and is typically installed at the base of a roof or wall to create a seal that prevents water from seeping into the structure. This function is essential in maintaining the integrity of the roofing system by ensuring that water flows off the roof and away from vulnerable joints.

In contrast, extending beyond shingles addresses how water drainage is managed at the edges of roof installations, as it creates an overhang to ensure runoff does not backtrack under the shingles. Preventing debris accumulation is more about structural maintenance rather than the direct function of the base flashing itself. Sealing thermal expansion pertains to materials moving during temperature fluctuations, which does not specifically define the role of base flashing. Thus, the primary role of base flashing in a flashing system is effectively to ensure a water-tight barrier at critical junctions, demonstrating its significance in roofing practices.