What vertical tie spacing requires ties to be installed no more than 20 feet apart?

The appropriate vertical tie spacing of no more than 20 feet apart is applicable when the base width of the scaffold is less than 3 feet. This requirement is grounded in safety considerations, ensuring stability and load distribution. When the base width is narrower, the scaffold is inherently less stable, which necessitates closer vertical tie spacing to maintain structural integrity and prevent tipping or swaying.

A base width greater than 3 feet can provide more inherent stability, allowing for ties to be spaced further apart since the structure can better withstand lateral forces. With a base width of exactly 3 feet, the stability is sufficient to allow for a similar spacing of ties as with a wider base, but less than 3 feet heightens the risk. Therefore, the safety regulations stipulate that for scaffolds with a base width less than 3 feet, the ties must be more closely installed, ensuring enhanced support and safety for the workers on the scaffold.