The 10″ thick concrete cap on this rubble trench foundation represents a significant reduction in the amount of cement used as compared to current conventional building standards.
The gravel in a rubble trench foundation allows any water in the ground under the building to flow to the bottom of the trench and away from the building through the drainage trench, preventing moisture problems or frost heave.
Concerned about the amount of embodied energy in concrete? An excellent way minimize concrete in the foundation for a building is to use a rubble trench.