What is a critical function of counter flashing?

Counter flashing serves a crucial role in protecting a building from water intrusion. Its primary function is to act as a waterproof barrier where the roof meets vertical surfaces, such as walls or chimneys. By being installed atop the base flashing, counter flashing directs water away from the intersection of the roof and wall, preventing moisture from seeping in and causing potential damage to the structure.

This function is particularly vital in maintaining the integrity of the roof and ensuring a durable building envelope. Properly installed counter flashing significantly reduces the risk of leaks, which can lead to more serious issues like mold growth, structural decay, and increased repair costs over time. Therefore, its ability to waterproof the interface between the wall and roof makes it an essential element in roofing construction and repair.