As seen in the image above, ponding water on flat roofs can cause serious damage to your property. When water accumulates and stagnates for more than 48 hours on a roof, it is called water ponding. The drainage system may not be adequate to support the roof structure, or other problems with the roof design and building infrastructure can cause large puddles on the surface. The liquid cannot evaporate from the roof because of the volume.

Standing water for 12 to 36 hours on a roof after a storm is normal. However, according to the National Roofing Contractors Association, any standing water that has been on a roof for more than two days should be checked by a commercial roofing contractor.

Gravity forces cause water to accumulate on flat roofs, as the only way for it to go is down. Over time, ponding water can pose a serious risk to a flat roof system and needs to be addressed to ensure the structural integrity of a building.

Quality of roofing materials vs. workmanship

According to Martin J. Fradua of the University of Massachusetts, most roof membranes are not waterproof; they are only water-resistant. It is important to know this when considering the potential damage caused by water accumulation. Although most membranes on flat roofs can keep water out, they only last so long, particularly if heavy volumes of water are accumulating.

Even the best roofing materials cannot prevent ponding water. We recommend that you choose a roofer with experience who will do the job right the first time. Although membrane, flashing, and other roof material quality are important, you can’t just buy the best material and expect not to have water ponding problems.

You will save money by choosing the best roofer for your city. This will prevent you from having to pay for unnecessary repairs and maintenance.

This post was written by Ted Williams! Ted is the owner of, one of the best roofing companies in Saint Petersburg, FL! Ted is a Master Elite Weather Stopper GAF Roofing Contractor, a double award winner of Best Steep-Slope Contractor from GAF and achiever of Master Elite Consumer Protection Excellence from GAF. He has been serving the Pinellas County area since 1978.  Old Time Roofing has a tradition of quality workmanship, servicing residential and commercial properties.