What does counter flashing cover?

Counter flashing is a key component in roofing systems, particularly in the areas around walls, chimneys, and other projections where roofing meets vertical surfaces. Its primary function is to prevent water from seeping into the structure at these critical junctions.

The correct answer, which identifies counter flashing as covering the top edge of base flashing, helps to create a watertight seal between the roofing system and the vertical elements. By overlapping the top edge of base flashing, counter flashing effectively directs water away from the seams and helps to prevent leaks that could compromise the structure's integrity.

In contrast, the other choices focus on areas that are not specifically addressed by counter flashing. While window edges, roofing seams, and edges of walls are important in overall construction and waterproofing, they do not encompass the particular role that counter flashing plays in coordinating with base flashing to ensure proper drainage and moisture management in roofing applications.