Have a flat roof and noticed that rainwater has started to pool there? This could be a sign of a roofing problem called ponding, which affects many flat roofs – especially in rainy countries like the UK.
Below, we’ll take a look at what ponding water is and why it’s a bad thing for your roof. Plus, the warning signs that a small puddle could be turning into a major headache, and when to arrange preventative roofing repairs or maintenance work.
What Is Roof Ponding?
Roof ponding is pretty much what it sounds like – it’s where a puddle of standing water gathers on a flat roof. It may start small, but can soon start to look like a small pond after a few days of heavy rainfall.
It happens when the roof doesn’t have sufficient drainage, or if there is a clogged drain or gutter preventing the water from draining away.
Another common cause of roof ponding is compressed insulation. If the roof has ever been walked or stood upon (such as to clean upstairs windows, for example), this extra weight can cause a dip where the insulation materials underneath get squashed. And this dip can be the start of your roof ponding problem.
Isn’t It Normal for Flat Roofs To Have Puddles?
You might think that some puddling or ponding is perfectly normal on a flat roof. The surface is flat after all, with no angled slope to let rainwater drain away like on a pitched roof.
But the truth is that no flat roof should actually be perfectly, completely flat. If designed and installed properly, there should be the slightest slope to allow the roof to drain water away during wet weather. From ground level, you might not be able to see this gently rising pitch, but it should be there.
Of course, if the roof hasn’t been installed properly and it is actually perfectly flat, there’s always the risk of ponding occurring.
Despite this, it isn’t uncommon for flat roofs to have some standing water remaining following heavy rain. But this should drain away over time. According to the National Roofing Contractors Association (NRCA), it counts as ponding if the water doesn’t drain within 24 to 48 hours.
The Dangers of Roof Ponding
Any amount of standing water on a flat roof can cause problems, even if it eventually drains away. This is due to the excess weight of it, which can cause stress to roof trusses, joints and even the building’s structure. Constant exposure to water can also erode roof materials and potentially cause leaks.
You might also spot other signs of ponding-related problems, such as the growth of moss and algae. Like with other types of roof, you don’t want too much of this growing on your flat roof. It holds a lot of moisture, which can cause even more weight and pressure on the roof surface.
Roofing Repairs To Fix Ponding Water Problems
If you have standing water on your flat roof and it’s not draining away, you may need to call in a roofer. It’s best not to leave it until the puddle turns into a pond.
Call in a roofing professional to take a look, as they may be able to carry out a simple fix like unblocking a drain or gutter. This shouldn’t cost too much, and it can instantly fix many roof ponding problems.
Your roofer can also tell you if larger preventative measures or repairs are needed, to help you prevent expensive emergency work later on.