In concrete structures, shoring should start at least how many good floors below the damaged level?

• A. One
• B. Two
• C. Four
• D. Three

Answer: (D)

Stabilizing a damaged concrete structure requires shoring that is anchored on solid, undamaged levels well below the damage so the load can be safely redirected away from the compromised area. Placing shoring starting three good floors below the damaged level provides a safe margin against progressive failure: if the upper portion of the structure settles, shifts, or if adjacent floors crumble, the shoring system still sits on multiple intact levels to carry and transfer the load down to a stable base. This spacing also offers space for crews to work and inspect, while reducing the risk that the bearing surfaces are compromised by debris or movement in the damaged zone. Starting only one or two floors below could risk undermining the shoring if those floors are damaged or weakened, and going four floors below, while protective, can hinder access and speed of operations. Three floors below represents the practical minimum to maintain stability and safety in this scenario.