Where must flashing at exterior window and door openings extend?

Flashing at exterior window and door openings is a critical element of building envelope design, particularly for preventing water intrusion. The correct practice requires that the flashing extend to the surface of the exterior wall finish. This positioning is essential because it ensures that any water that might enter the opening can be properly directed out and away from the structure, rather than being trapped and potentially causing damage to the framing or interior finishes.

By extending the flashing to the surface of the exterior wall finish, it provides a continuous barrier that channels water away and prevents it from seeping into the walls. This detail is necessary for maintaining the integrity of the building envelope and protecting it from moisture-related issues. The improper placement of flashing, such as extending it to the building foundation or the top of window frames, does not adequately address the need to direct water effectively away from the structure, thus increasing the risk of potential leaks and damages to the building structure.