All it takes is a little moisture and those feather-light leaves biodegrade into a soggy, heavy mass that clogs drains, blocks scuppers and invites mold, fungi and mildew. If not promptly removed, leaves and debris can lead to backed-up water, which increases the live load on the roof deck. Standing water, just 1-inch deep, adds five pounds per-square-foot of live load on the roof assembly. Over time, standing water can leach the pliable properties out of some single-ply membranes, reducing flexibility and the life of the roof.
In the winter, ponding becomes critical when pooling water freezes and expands, forcing its way into tiny cracks or under flashings. Additional ice weight can cause structural damage and expensive repairs, or – in extreme cases – even roof collapse.