Under what condition might scaffolding not require sills?

The correct condition under which scaffolding might not require sills is when it is erected on concrete surfaces. This is primarily because concrete provides a stable, solid foundation that can support the weight of the scaffolding and the loads it bears.

Sills are generally used to distribute the weight of a scaffold over a larger area and provide additional stability, particularly on softer or uneven ground where the risk of sinking or tipping is greater. In contrast, a concrete surface typically does not present the same risks, making the use of sills unnecessary. Other conditions, such as soft or uneven surfaces, often necessitate additional support to ensure safety and stability, whereas a well-placed scaffolding on concrete can maintain its integrity without them.