Every year in the United States commercial buildings are extensively damaged or destroyed by the affects of rooftop ponding water. While this is an issue commercial buildings need to watch out for, home owners with flat roofs also need to be aware of the possible affects of ponding water.
Roofing professionals always encourage business owners to inspect their flat roofs following rain to see if they might be at risk of a roof collapse because of poor drainage issues.
Ponding water is defined as the water which remains on a roof 48 hours or more. Ponding water weighs approximately 5 lbs. per inch, per each square foot of roof surface. A ponding 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!
In order to avoid ponding water, the flat roof would need to have some sort of pitch, slope or roof drains. Ponding water seriously increases the load on the roof assembly, and as water accumulates, deck deflections (sags) can increase, resulting in more ponding water. When this happens, the structural integrity of the decking can be compromised.
Most roof warranties are voided in areas that pond water for more than 48 hours. Additionally, ponding areas rot roofing membranes, attract dirt and algae, and quickly destroy 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. Commercial buildings with massive square footage are at increased risk.
Have your roof inspected frequently, especially after a good rain to avoid future problems or at worst premature roof replacement.
Let a roofing specialist from Pyramid Roofing evaluate your roof.