At what depth should foundation/footing drains be installed?

The correct choice indicates that foundation or footing drains should be installed at or below the area to be protected. This is critical because the primary purpose of foundation drains is to prevent water from accumulating near the foundation of a building, which can lead to structural issues such as cracks, shifting, or even flooding in the basement or crawl space areas.

When installed at or below the area being protected, the drains can effectively capture and redirect groundwater or surface water away from the foundation. This helps maintain the integrity of the structure and prevents moisture-related problems. By allowing water to flow freely into the drainage system, the risk of water pressure building up against the foundation walls is minimized.

In contrast, other depth options could lead to potential water intrusion problems. For instance, installing drains at the surface level would be ineffective, as it wouldn't allow for the collection of subsurface water. Similarly, depths that are too far above the foundation, such as one foot above or two feet below grade, could result in poor drainage performance, increasing the likelihood of water-related issues.