What does foundation drainage primarily remove from the foundation's perimeter?

Foundation drainage is crucial for maintaining the integrity of a building's foundation. Its primary function is to manage and control water accumulation around the foundation's perimeter. By removing free water, which is liquid water that can gather due to rainfall, groundwater, or surface runoff, foundation drainage systems help to prevent hydrostatic pressure from building up against the foundation walls. This pressure can lead to serious issues such as water infiltration, soil erosion, and structural damage.

When drainage is properly implemented, it ensures that water does not pool around the foundation, thus protecting it from damp conditions that could lead to mold growth, wood rot, and other moisture-related problems. Managing free water effectively is essential for long-term durability and stability of the building.

In contrast, options like excess soil, water vapor, and air pockets do not directly pertain to the primary concern of water management at the foundation level. Excess soil can be a concern during excavation or grading but is not related to the function of drainage systems, while water vapor and air pockets are more about moisture dynamics and aeration rather than direct water management.