On a site with expansive soil, roof drainage water should discharge at least how many feet from the foundation walls?

Discharging roof drainage water at least 5 feet from the foundation walls is important to prevent soil erosion and maintain the structural integrity of a building, especially in areas with expansive soils. Expansive soils are prone to significant volume changes with moisture variations, which can lead to ground movement and potential damage to the foundation.

When water is allowed to pool too close to the foundation, it can increase the moisture content in the surrounding soil, exacerbating the swelling and shrinking cycles of expansive soils. By ensuring that water is discharged at least 5 feet away, there is a reduced risk of causing such adverse effects. This distance helps to keep the foundations stable and mitigates the potential for structural damage over time, ensuring the longevity and safety of the building.

While other distances may be considered in different contexts or for various soil types, the 5-foot benchmark is widely accepted for managing drainage effectively in expansive soil areas.