Chronic ponding on a roof is most likely caused by which combination?

Chronic ponding on a roof is most likely caused by which combination?

• A. High wind uplift and flat roofing.
• B. Sharp edges only.
• C. Structural deflection, long spans, insulation compression, or poor tapered layout.
• D. Excessive adhesive usage.

Answer: (C)

Water on a flat roof sticks around when the surface isn’t sloped enough to shed it toward the drainage points. The most likely culprits are factors that directly affect the roof’s drainage geometry: structural deflection that lets the deck sag, long spans that lack intermediate support and sag between framing, insulation compression that flattens or reduces the intended slope, and a poor tapered insulation layout that fails to create the necessary gravity-driven slope toward drains. When any of these conditions exists, water will collect in low spots rather than run off, leading to chronic ponding. Other listed factors don’t tie as tightly to drainage geometry. High wind uplift and flat roofing can impact membrane performance and leakage, but they’re less about creating persistent low spots. Sharp edges don’t establish a drainage slope, and excessive adhesive usage isn’t a primary driver of ponding.

Water on a flat roof sticks around when the surface isn’t sloped enough to shed it toward the drainage points. The most likely culprits are factors that directly affect the roof’s drainage geometry: structural deflection that lets the deck sag, long spans that lack intermediate support and sag between framing, insulation compression that flattens or reduces the intended slope, and a poor tapered insulation layout that fails to create the necessary gravity-driven slope toward drains. When any of these conditions exists, water will collect in low spots rather than run off, leading to chronic ponding.

Other listed factors don’t tie as tightly to drainage geometry. High wind uplift and flat roofing can impact membrane performance and leakage, but they’re less about creating persistent low spots. Sharp edges don’t establish a drainage slope, and excessive adhesive usage isn’t a primary driver of ponding.