To what minimum depth should material classified as rock be excavated below subgrade?

The correct depth for excavating material classified as rock below subgrade is set at 6 inches. This specification is crucial because rock can impede proper drainage, support, and grading of the surface that will be laid above. By excavating this minimum depth, it ensures that the foundation is stable and capable of supporting infrastructure such as roads, which might otherwise be negatively affected by the presence of rock.

Excavating below this specified depth reduces the risk of future settlement issues and provides a more uniform, workable substrate for subsequent construction activities, ensuring longevity and stability in the finished project. Understanding these underlying principles assists in the planning and execution of excavation work, ensuring compliance with engineering standards and promoting the integrity of the surface work.