What is Ponding Water: Ponding water is defined as the water which remains on a roof 48 hours or more.

Most flat roofs require some sort of pitch or slope to avoid ponding water. But unfortunately, ponding water occurs on most flat roofs. Ponding water can seriously increase the load on a roof assembly. As water accumulates, deck deflections (sags) can increase, resulting in more ponding water which could compromise the structural integrity of the deck.

Ponded water creates hydrostatic pressure that forces water into even the tiniest pinhole imperfections. This is why most roof warranties are voided in areas that pond water for more than 48 hours. Additionally, ponding areas rot roofing membranes, attract dirt/mud and algae, and quickly destroy any reflectivity of reflective coatings.

By far the biggest risk associated with ponding water is weight and the potential for damage to the roof deck or collapse of the decking system.

Ponding water weighs approximately 5 lbs. per inch, per each square foot of roof surface. A ponded area 20'x20' at 1" deep would equal 400 total square feet at 5 lbs per foot or a roof live weight of 2,000 pounds!

That can be an additional ONE TON of live roof load of stress on your building's roof!

Ponding Water Can Become a Serious Health Issue: If water stays on your roof several health issues can arise. Warming water facilitates the growth of algae, mixed with pigeon feces can create harmful fungal material that could effect the air quality in your building.

Have your roof inspected frequently, especially after a good rain to avoid future problems or worst premature roof replacement.