What hazard is associated with deck components when a single-ply roof membrane is present?

• A. Decking remains unaffected.
• B. Decking resists fire.
• C. The membrane seals all heat.
• D. Decking can burn under the membrane.

Answer: (D)

Heat and fire can be trapped under a single-ply roof membrane, allowing the wood decking beneath to ignite even while the membrane on top still looks intact. The membrane is a thin covering and doesn’t stop heat transfer or prevent burn-through to the decking; embers or sustained heat can start the decking burning without immediate visible signs above. This hidden fire can spread and compromise the structure before it’s noticed, which is why decking burning under the membrane is the hazard. The other ideas aren’t right because wood decking is combustible and the membrane doesn’t perfectly seal heat or prevent ignition.