What is the name of a water impermeable material used to divert collected water away from a wall system?

The correct answer is flashing, which refers to the material designed to direct water away from a wall system, preventing moisture from entering and causing damage. Flashing is typically installed in various areas of a building, especially where there are joints or penetrations that are at risk of water intrusion, such as windows, doors, and rooflines. Its water impermeable properties make it an essential component in effective waterproofing and moisture management strategies in masonry construction.

Flashing is commonly applied over the top of windows and doors and at roof edges to ensure that any water that runs down the wall or roof can be redirected away from these vulnerable areas. This helps to maintain the integrity of the structure and prolong its lifespan, showcasing its critical role in masonry and construction.

Other materials such as tar paper, sealant, and weep holes serve different functions within the construction and masonry process. While they all contribute to managing water, they do not perform the same direct diversion role that flashing does. Tar paper is usually used as a moisture barrier beneath roofing materials, sealants are applied to create airtight seals around joints and openings, and weep holes allow drainage within masonry walls, but they do not actively direct water away from the structure in the same way flashing does.