Which construction type is most likely to fail within 5 minutes when exposed to direct heat due to lightweight exterior walls?

Which construction type is most likely to fail within 5 minutes when exposed to direct heat due to lightweight exterior walls?

• A. Type II
• B. Type V
• C. Type I
• D. Type IV

Answer: (B)

The main idea is how fire resistance differs with construction materials, especially when exterior walls are lightweight and combustible. Type V uses wood-frame construction with lightweight exterior walls, so the framing and sheathing are highly susceptible to ignition and rapid flame development. When exposed to direct heat, the wood components can ignite quickly, lose strength fast, and can lead to structural failure in a short time—often within minutes. Other construction types rely on noncombustible or heavier elements and generally offer greater resistance to direct heat: fire-resistive or noncombustible systems resist flame longer, and even ordinary masonry exterior walls slow heat transfer. Heavy timber (Type IV) can char and maintain some strength for a while, providing more fire resistance than lightweight wood, though it’s not immune. So, in a scenario with direct heat and lightweight exterior walls, the configuration that is most prone to rapid failure is the wood-frame, lightweight-walled Type V construction.

The main idea is how fire resistance differs with construction materials, especially when exterior walls are lightweight and combustible. Type V uses wood-frame construction with lightweight exterior walls, so the framing and sheathing are highly susceptible to ignition and rapid flame development. When exposed to direct heat, the wood components can ignite quickly, lose strength fast, and can lead to structural failure in a short time—often within minutes.

Other construction types rely on noncombustible or heavier elements and generally offer greater resistance to direct heat: fire-resistive or noncombustible systems resist flame longer, and even ordinary masonry exterior walls slow heat transfer. Heavy timber (Type IV) can char and maintain some strength for a while, providing more fire resistance than lightweight wood, though it’s not immune.

So, in a scenario with direct heat and lightweight exterior walls, the configuration that is most prone to rapid failure is the wood-frame, lightweight-walled Type V construction.