Ponding water is water that remains on a roof for 48 hours or longer. Ponding water can come from precipitation, leaking cooler lines and pans, AC-condensate lines and pans, and condensation. Water that accumulates on the roof can cause serious damage.
Ponding water can significantly increase the amount of weight on the roof deck. This can lead to deck deflections and additional ponding that could compromise the deck’s structural integrity.
If water is allowed to stand on a roof for a long period of time, it can allow algae and vegetation to grow. This can damage the roof membrane, clog drains, and lead to more ponding.
Ponding water also allows dirt, debris, and other contaminants to accumulate. These can damage the membrane surface.
Ice forms and moves constantly on a roof as temperatures change. This can “scrub” the membrane and cause physical damage.
Over time, ponding water can accelerate erosion and deterioration of the membrane surface and lead to the failure of the roof system. Even small amounts of moisture under the roof membrane can reduce the insulation’s thermal efficiency. Moisture can cause serious damage to the roof deck, insulation, and membrane and the interior of the building.
Proper design, installation, and maintenance can prevent ponding water. Several roofing organizations recommend that a roof have a minimum slope of ¼ inch per foot to allow water to drain freely and avoid ponding.
Check AC units, coolers, and drains for roof debris or patching materials that are blocking exits. Remove any loose mineral granules to prevent them from trapping moisture.
If these measures do not correct the problem, contact a professional roofing contractor. It may be necessary to re-patch the roof, open existing drains, install new drains, or take other steps to eliminate ponding water.