To prevent moisture intrusion behind sidewall flashing, what type of flashing must be installed at brick and stone walls?

The installation of counter-flashing is crucial for preventing moisture intrusion behind sidewall flashing at brick and stone walls. Counter-flashing involves placing a flexible, weather-resistant material over the top edge of the sidewall flashing. This creates a barrier that directs water away from the wall and prevents it from seeping behind the flashing.

In masonry applications, such as brick and stone, it is essential to ensure that water that runs down the wall cannot penetrate behind the flashing, which could lead to water damage, mold growth, or structural issues. Counter-flashing effectively seals the junction where the sidewall flashing meets the taller vertical surface of the masonry, thus minimizing the risk of water intrusion.

Other types of flashing, while valuable in their own contexts, do not serve the specific function required at brick and stone walls as effectively as counter-flashing. For example, step-flashing is primarily used in shingle roofing systems where the roof meets a wall. Base-flashing is designed to protect horizontal surfaces, and diverter flashing works to redirect water at roof valleys or chimneys. While all these types of flashing have their specific applications, counter-flashing is uniquely suited to address moisture intrusion issues at the termination point of wall flashings against vertical surfaces in masonry construction.