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What is the minimum thickness of crushed stone required above the footing for foundation drains?

  1. A. 4 inches

  2. B. 6 inches

  3. C. 9 inches

  4. D. 12 inches

The correct answer is: B. 6 inches

The minimum thickness of crushed stone required above the footing for foundation drains is established to promote proper drainage and ensure stability of the foundation. A minimum thickness of 6 inches of crushed stone is recommended because it provides sufficient space for water to flow and be effectively channeled away from the foundation without causing any obstruction or pressure buildup. The use of crushed stone in this context is pivotal as it helps maintain a certain level of porosity, allowing for the free passage of water while also facilitating proper grading around the foundation. Adequate thickness ensures that the crushed stone layer can accommodate the dynamic forces at play, such as hydrostatic pressure from groundwater, which is critical in preventing settling or shifting of the foundation. Having less than this recommended thickness could potentially result in inadequate drainage and may compromise the integrity of the structure over time.