What is the function of flashing behind openings in stucco construction?

• A. To add decorative trim
• B. To divert water away and prevent infiltration
• C. To improve thermal conductivity
• D. To reduce mass

Answer: (B)

Moisture management in stucco assemblies is being tested. Flashing behind openings is there to divert water that gets behind the stucco away from the wall sheathing and toward the exterior, preventing water infiltration and potential damage. Around windows and doors, the flashing creates a dedicated drainage path so any water that sneaks behind the stucco can flow out rather than soaking into the framing. It also helps break capillary action, reducing wicking of moisture into the wall. By directing water to the exterior and to weep paths, flashing protects the structural backing and keeps the interior dry. Decorative trim, improving thermal conductivity, and reducing mass don’t address this moisture-control role.