The portion of the flashing attached to a vertical surface to prevent water from migrating behind the base flashing is called?

• A. Base flashing
• B. Caulk
• C. Cap flashing
• D. Certificate of Compliance

Answer: (C)

Cap flashing is the portion that sits on the vertical surface and covers the top edge of the base flashing, forming a cap that prevents water from migrating behind the base flashing. It overlaps and seals the joint so water is directed down the wall rather than seeping behind the flashing. In a roof-wall intersection, this piece is essential because the base flashing alone can’t stop water from migrating behind it if the top edge isn’t protected. Base flashing lies along the roof plane, while cap flashing covers the edge on the vertical side. Sealant (caulk) is a different material, and a certificate of compliance isn’t a flashing component.