A disadvantage of metal roofs to firefighters is that they may be built over an existing roof.

• A. Lightweight
• B. Non combustible
• C. Fireproof
• D. May be built over existing roof

Answer: (D)

The main idea is how roof construction affects firefighting tactics. If a metal roof is installed over an existing roof, you end up with multiple layers of roofing. This creates hidden spaces where fire can spread without being seen, makes ventilation more difficult because you have to cut through extra material, and increases the risk of structural problems or collapse under firefighting operations. The material’s properties—being noncombustible, fire resistant, or lightweight—don’t by themselves create this layered-risk issue; those qualities are beneficial or neutral. The practice of layering a metal roof over an existing roof directly adds complexity and danger for firefighters, which is why this option represents the disadvantage.