Glossary
Ponding water
Water that remains on a roof surface more than 48 hours after rainfall ends — a leading accelerant of membrane aging and a common warranty exclusion.
Plain-English definition
If water is still sitting on your roof two days after it stopped raining, that’s ponding water. Roofs are designed to shed water; where it collects instead, the membrane ages faster, debris accumulates, and structural load increases.
Why it matters to you
NRCA defines ponding as water remaining 48 hours or longer after rainfall under conditions conducive to drying, and manufacturer warranties commonly require positive drainage or exclude damage from standing water (ARMA — Ponding Water Basics). A primary NRCA citation still needs to be obtained before this term can publish — an earlier draft linked a third-party mirror of an NRCA document, which does not meet CRI’s sourcing standard and has been removed. Remediation typically means drainage correction: added drains, scuppers, or tapered insulation.
Technical detail
Placeholder: drainage-design causes (deck deflection, blocked drains, inadequate slope), measurement conventions, and code references.