Which of the following describes a ventilation-related drawback of single-ply roof systems?

• A. Easy to vertically ventilate.
• B. Difficult to vertically ventilate.
• C. Has no impact on ventilation.
• D. Improves smoke extraction.

Answer: (B)

Vertical ventilation relies on quickly creating openings in the roof to release heat and smoke. On a single-ply roof, the surface is a smooth, continuous membrane over insulation and decking, with few natural voids or guiding features to help locate and safe-cut a vent. Any hole must go through the membrane and multiple underlying layers, which can be slow, awkward, and tricky to control. The membrane is slippery, can tear or shift when cut, and there’s a risk of compromising the roof or pushing fire into hidden pockets if the vent isn’t placed and managed carefully. All of this makes establishing an effective vertical vent on a single-ply roof more difficult, which is the main drawback.