Which factor is associated with early collapse during a fire?

• A. Lightweight Construction
• B. Steel Frame Construction
• C. Concrete Masonry
• D. Timber Frame

Answer: (A)

Lightweight construction is associated with early collapse because its structural members have little mass and rely on thin, engineered components and simple connections. When exposed to fire, these elements heat up quickly, lose strength and stiffness fast, and can fail or buckle abruptly, causing floors or roofs to give way sooner than heavier, more massed construction. Concrete masonry and heavy timber (timber frame) resist fire more effectively due to their greater mass and protective char layers, so they don’t typically collapse as quickly. Steel frames can be vulnerable if unprotected, but the standout factor for rapid collapse is the lightweight nature of the members and connections.