What is the purpose of the dam used on window flashing?

The purpose of the dam used on window flashing is to hinder water flow behind siding. This is crucial in building design and construction, as water intrusion can lead to significant damage over time. By integrating a dam into window flashing systems, it effectively directs any water that penetrates or accumulates around the window away from the building structure. This helps to prevent moisture-related issues such as mold growth, wood rot, and deterioration of building materials, which can compromise the integrity and longevity of the structure.

The design of the dam functions to create a barrier that stops potential water flow from moving in unwanted directions, particularly behind the siding where it would be difficult to detect and mitigate. This capability is essential for maintaining a dry envelope around the windows and, by extension, the entire building.

Understanding this function not only underscores the importance of proper installation and waterproofing techniques but also highlights why window flashing and the associated components like a dam are critical considerations in building practices.