What must supported scaffold poles, legs, frames, and uprights bear on?

The requirement for scaffold poles, legs, frames, and uprights to bear on firm foundations is critical for ensuring the stability and safety of the scaffold structure. A firm foundation provides a solid and level surface that can adequately support the weight of the scaffold along with any loads it may carry, such as workers, materials, and equipment. This minimizes the risk of tipping, shifting, or collapsing under stress.

Firm foundations, such as concrete, asphalt, or well-compacted soil, allow for even weight distribution and reduce the chances of settlement or uneven load, which could lead to structural failure. Using unstable surfaces or soft ground would diminish the integrity of the scaffold, possibly leading to accidents and injuries on the worksite. Elevated platforms, while they can hold scaffolding, do not ensure the necessary support unless they are themselves stable and secure. Thus, the emphasis on firm foundations is essential for maintaining workplace safety standards and compliance with safety regulations.