What is the maximum permissible span for a 1 ¼ in. x 9 in. or wider wood plank used as a scaffold plank with a 50 lb./ft.² load?

The maximum permissible span for a wood plank used as a scaffold plank is determined based on its width and the load it must support. In this case, for a 1 ¼ inch by 9 inch plank with a specified load of 50 pounds per square foot, the reference guidelines indicate that a span of 4 feet is acceptable.

This standard takes into account various factors, including the material's strength, thickness, and the loading conditions. A wider plank, like the one described, can typically support a greater load over a longer span compared to a narrower plank. The load per square foot is also reasonable for scaffolding applications, reinforcing that a 4-foot span is within safe limits.

Choosing a span greater than 4 feet would compromise safety by increasing the risk of deflection or failure under load. Therefore, the span of 4 feet ensures that the plank maintains structural integrity while providing adequate support for workers and materials on a scaffold.