If your commercial property has a flat roof, you’ll need to protect it from water damage. Although called "flat," horizontal rooflines feature a slight incline that helps promote drainage and prevent pooling after heavy rainfall. A rooftop with low spots or drainage issues may experience ponding, or when water accumulates and cannot drain. Learn more about ponding, including solutions for treating it, in the guide below.

Why Ponding is Harmful

Because flat roofs are slightly sloped, ponding water is often an indication of a larger drainage issue that should be addressed. When left unchecked, standing water can weaken the structure of your roof, creating cracks or holes. It can also contribute to water damage such as rot and mold.

When left for extended periods, ponding water can collect dirt, which may cause vegetation such as algae or moss to grow on your rooftop. Pools of water can also magnify UV rays from the sun, deteriorating the surface of your roofing materials. 

How to Spot Ponding and Low Spots

It's natural for a flat roof to collect some water during periods of heavy rain. On a roof with proper drainage, water accumulations will typically drain off within a day or two. If water pools are still deeper than an inch after 48-hours of dry weather, you'll want to look for low spots or obstructions in your drainage.

Low spots occur when the decking beneath the roofing membrane has deflected or sagged below the depth of the roof gutters. Because water always travels to the lowest point, it accumulates in the low spots rather than running off towards the scupper or gutter.

You can identify low spots in dry weather by looking for dried marks indicating past ponding. If there are none, consider spraying your roof down with a garden hose to help identify problem areas.

How to Treat Ponding

There are a variety of ways to resolve rooftop ponding depending on the cause. The most common solution is to unclog gutters, drains, and channels, removing any obstructions that are inhibiting water runoff.

For low spots, consider using liquid patching materials, roof patch putty, sheet fillers, or asphaltic fills to even out the surface of your roof. If the ponding is caused by an inadequate slope, consider hiring a roofing contractor to correct the pitch or install additional drainage to compensate for the lack of incline. 

If you're experiencing ponding on your commercial rooftop, contact the professionals at Quality Enterprise in Waynesboro, VA, for repairs. For over 30 years, their team of experts has provided high-quality roof restorations, repairs, and installations for both commercial and residential customers. Contact them today at (540) 949-0566 to request a quote, or visit their website to learn more about their services.