What is the purpose of counter flashing?

Counter flashing serves a crucial role in roofing systems, particularly where the roofing material meets vertical surfaces like masonry walls. Its primary purpose is to prevent water from penetrating behind the flashing and into the building envelope, which could lead to water damage and associated issues like mold growth or structural deterioration.

Counter flashing is typically installed above the base flashing, creating a barrier that diverts water away from wall penetrations or seams in the roofing system. When properly integrated, it ensures that any water that runs down the wall or roofing surface is channeled away from vulnerable areas, thus maintaining the integrity of the roofing system and the structure it protects.

While other options touch on concepts related to building performance, none directly address the specific function of counter flashing, which is fundamentally centered around water protection in roofing applications.