When exposed to fire, lightweight construction has catastrophic failure in how many minutes?

When exposed to fire, lightweight construction has catastrophic failure in how many minutes?

• A. 8-12 minutes
• B. 15-20 minutes
• C. 25-30 minutes
• D. 5-7 minutes

Answer: (D)

Lightweight construction fails quickly in fire because there isn’t much mass to absorb heat, and the thin members and connections lose strength rapidly once exposed to flames. The heat causes glue bonds to weaken and metal fasteners or steel components to fail, so the load-bearing capacity collapses in a short, dramatic time frame. In typical fire exposure, catastrophic failure can occur within about five to seven minutes. That’s why these assemblies are known for early collapse and why crews treat areas with lightweight trusses as high risk early in a fire. Longer times wouldn’t match how quickly these structures reach critical temperatures and lose strength.

Lightweight construction fails quickly in fire because there isn’t much mass to absorb heat, and the thin members and connections lose strength rapidly once exposed to flames. The heat causes glue bonds to weaken and metal fasteners or steel components to fail, so the load-bearing capacity collapses in a short, dramatic time frame. In typical fire exposure, catastrophic failure can occur within about five to seven minutes. That’s why these assemblies are known for early collapse and why crews treat areas with lightweight trusses as high risk early in a fire. Longer times wouldn’t match how quickly these structures reach critical temperatures and lose strength.