Footings shall be stepped when the ground surface slopes more than what ratio?

• A. more than one unit vertical to ten units horizontal
• B. more than two units vertical to ten units horizontal
• C. more than one unit vertical to five units horizontal
• D. more than three units vertical to ten units horizontal

Answer: (A)

When determining the appropriate stepping of footings, the critical factor is how steep the ground surface slope is in relation to horizontal distance. The standard practice is to step footings when the slope exceeds a vertical to horizontal ratio of more than one unit vertical to ten units horizontal. This guideline is grounded in ensuring the stability and integrity of the foundation in sloped conditions.

A slope of greater than one vertical to ten horizontal indicates a mild incline where there could be potential issues with soil erosion or instability if the footing does not adequately address the slope. Stepped footings effectively distribute the load of the structure across a larger area, accommodating the natural topography and providing additional support against lateral soil pressures.

This stepping method reduces the risk of foundation movement or failure by allowing for proper drainage and effectively managing the weight distribution of the building across the uneven ground surface. Thus, recognizing the importance of this particular ratio is crucial for maintaining the safety and stability of structures built on sloped terrain.