We are often asked to articulate a position on ponding water and whether we warrant ponding water. Our answer is multifaceted as the concerns are much more than just possible membrane degradation. After all, the simple purpose of a roof is to shed water off and away from the building.
Ponding water in itself will have no adverse effect on the FiberTite Single Ply Roof membrane, but careful consideration must always be given to the possible increase of structural live loads associated with excessive "standing water".
Commercial Roofing Warranties do not cover structural damage, collapse of the insulation, possible protrusion of the fasteners due to added live loads, condensation or deterioration of the insulation as a result of cyclical wetting and drying associated with excessive condensation that occurs due to the cooling effect the ponding water has on the membrane during times of increased vapor drive within the roof system.
Additionally, most roof system manufacturers specifically exclude ponding or standing water from their warranties. In some instances this can even include the presence of small bird baths. These warranty exclusions are due to possible degradation of the membrane due to algae, magnified UV, or accelerated heat aging due to discoloration of the roof surface in areas of ponding water.
Sloping a roof to drain is practical but sometimes even the best tapered systems can leave small areas of standing water that do not immediately drain. So what is the definition of ponding water? Our opinion runs parallel to the NRCA position on ponding as accumulative water that doses not disappear within 48-hrs of conditions conducive to drying.