What is the required back-onto-roof extension factor relative to the outboard distance for most scaffold setups?

What is the required back-onto-roof extension factor relative to the outboard distance for most scaffold setups?

• A. 1.0 times
• B. 1.5 times
• C. 2.0 times
• D. 0.5 times

Answer: (B)

When a scaffold projects out from a wall onto a roof, the section that extends back onto the roof serves as a counterbalance to the outward reach. To provide safe stability against tipping and sliding, that back-onto-roof portion is typically set at 1.5 times the outboard distance. In other words, the part going back onto the roof should be about half again as long as the part extending outward. For example, if the scaffold sticks out 4 feet from the edge, the back extension should be about 6 feet. This extra reach increases the base area behind the edge, helps keep the center of gravity within the support, and improves resistance to wind and loads. Using a 1.0x extension would offer less counterbalance, while a 0.5x is too short; a 2.0x extension would be more than what’s typically required for most setups.

When a scaffold projects out from a wall onto a roof, the section that extends back onto the roof serves as a counterbalance to the outward reach. To provide safe stability against tipping and sliding, that back-onto-roof portion is typically set at 1.5 times the outboard distance. In other words, the part going back onto the roof should be about half again as long as the part extending outward. For example, if the scaffold sticks out 4 feet from the edge, the back extension should be about 6 feet. This extra reach increases the base area behind the edge, helps keep the center of gravity within the support, and improves resistance to wind and loads. Using a 1.0x extension would offer less counterbalance, while a 0.5x is too short; a 2.0x extension would be more than what’s typically required for most setups.