Lyons Roofing

Hidden Consequences of Ponding on Your Flat Roof

What Happens When Water Collects on Your Roof?

A properly designed roof, even one that appears to be flat, is going to have some amount of slope to it to allow water to drain off of it after it rains. This is helped along by evaporation. If you notice that your roof still has water on it as much as two days after the rain has passed, you may be dealing with what is called “ponding.”

Ponding can occur for numerous reasons, including compacted insulation due to people frequently walking over certain areas, resulting in indentations, or drains that may have been improperly installed or are not functioning in optimal condition. Whatever the cause, ponding tends to be a cumulative problem – small ponds collect water, the weight of which will, over time, create a deeper indent and larger ponds, and so on. If you do not handle these issues, the water will begin breaking down the materials of your roof and cause even more drainage issues. There are also several other problems that are likely to crop up in the meantime. The most important thing to understand is that ponding is almost always present to some degree on a flat or low sloped roof. The AZ Registrar of Contractors have identified how to determine if your ponding requires attention- if the water is gone in 48 hours (2 days) it is a non-issue.


Bugs of all kinds are attracted to standing water. Mosquitoes are frequent visitors to these types of ponds, but there are many more that could decide to call your roof home. Not only are these insects nuisances whether you spend much time on your roof or not, their presence outside could start to cause problems for inhabitants within.


Ponds will attract birds just as surely as they attract bugs. Indeed, as many birds eat those bugs, they might be even more inclined to make themselves at home on your roof. However, birds nesting and squawking on your roof will almost certainly be disruptive, and their droppings tend to have a corrosive effect that will also wear down your roof.

Plant Growth

A roof with excess moisture is a place where many types of algae, weeds, and mold can take hold and thrive. This is not only unattractive but can make the roof materials break down even faster and lead to even more clogs in the roof drains.


Over time, water collected on your roof will begin to cause discoloration. Not only does this make the roof look unattractive and worn-down, it can also deteriorate the effectiveness of any reflectivity that is used to keep the property cool.

Ice Damage

In areas where the climate dips below freezing, those same ponds can turn into damaging ice that cause problems for the roof’s membrane. Because water expands when it freezes, the damage resulting from this particular issue can be a good deal quicker than the others.

When you notice even small ponds cropping up on your roof after the water should have evaporated, it is important to bring it to the attention of your trusted roofing team. Give Lyons Roofing a call at (520) 447-2522 today to get started!