Damage & Failure
What is Ponding?
Roofing Glossary · Damage & Failure
Definition
The accumulation of standing water on a flat or low-slope roof surface that remains for more than 48 hours after rain. Ponding is caused by inadequate roof slope, structural deflection, or blocked drains. It accelerates membrane degradation, adds structural load, and is a leading indicator of impending roof failure. Building codes require a minimum 1/4 inch per foot of slope on flat roofs to prevent ponding.
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