Which collapse pattern occurs when the floor and or roof assemblies on both sides of a load bearing center wall collapse?

• A. Pancake
• B. Lean-to
• C. A frame
• D. V

Answer: (C)

When a load-bearing center wall fails, the floor and roof on both sides lose their primary support and drop inward toward the center. The remaining structure pulls together, creating a triangular, A-shaped silhouette with an apex at the center where the wall collapsed. This inward collapse on both sides is what defines the A-frame pattern.

This is different from a pancake pattern, where floors or the roof collapse into a stacked, multi-layered pile rather than forming a symmetric inward collapse; or a lean-to pattern, where only one side collapses, producing a slanted, leaning area; and from a V-shaped collapse, where debris forms a V opening due to asymmetric failure of walls.

Recognizing an A-frame collapse helps you anticipate the risk zone around the center and treat that area as highly unstable.