Without proper design, installation, and maintenance, a roof can suffer from ponding water, which can create a variety of adverse effects for the building.
According to the Asphalt Roofing Manufacturers Association (ARMA), ponding water is defined as the water that remains on a roof 48 hours or longer. The ARMA recommends that roof designs provide adequate slope (a minimum of one quarter-inch per foot) to guarantee the roof drains properly throughout the building’s life.
Typical issues that arise from ponding water on roofs include…
Accrual of dirt, debris and other impurities, which can mar the roof’s membrane.
Distortion of the roof deck’s construction, as ponding water can significantly swell the load. As water gathers, deck deflections can intensify, producing more ponding water that may adversely influence the structural integrity of the deck.
The emergence of algae and vegetation. If water is in place for extended intervals, algae and vegetation will probably result,