What additional load does ponding water add to a roof for every inch of depth?

Ponding water on a roof can create significant additional weight that must be supported by the roofing structure. Each inch of ponding water contributes a load of approximately 5 pounds per square foot. This figure is critical for structural engineers and roofing professionals to consider when assessing the integrity of a roofing system, especially in regions where heavy rain can occur, leading to the accumulation of water.

Understanding the implications of this weight is essential for ensuring that the roof can handle not just its structural load but also any environmental loads it might encounter, such as snow or standing water. The impact of ponding water can vary based on several factors, including the type of roofing material and the overall design of the building, which is why knowing the specific weight it adds is of paramount importance.