Ponding is defined as what?

• A. Standing water that remains longer than intended
• B. Rapid runoff
• C. Water infiltration into walls
• D. Evaporation of water

Answer: (A)

Ponding means water that sits on a roof surface and does not drain away as intended, remaining as standing water longer than expected. This description captures the condition you’re assessing when you see water puddling on a flat or low-slope roof after rainfall. It’s not rapid runoff, which would be water quickly moving off the surface, nor is it water that intrudes into walls (infiltration) or water simply evaporating. The reason this choice is best is that it directly describes a persistent, collect-and-remain situation on the roof rather than transient drainage behavior or leakage elsewhere.

Ponding is a concern because the standing water adds extra dead load to the roof, can promote membrane deterioration, and may lead to leaks or freeze-thaw damage if conditions are right. In practice, drainage problems are often identified when water remains for a significant period, commonly around 48 hours after a rain event, signaling that the roof’s slope or drainage systems aren’t functioning as designed.