While you may think having a few puddles of water on your flat roof is normal, it can be a sign that you’ve got bigger problems. If not addressed, ponding can lead to vegetation or mold growth, which can damage your roof membrane, or to freezing, which can add additional weight and pressure to your roof system. Ponding is a significant risk to your roof if left unchecked and not addressed promptly.
Although choosing the best roofing material for your flat roof is important, roof design is critical to avoiding ponding. Ensuring proper roof slope and adequate drainage reduces the likelihood of ponding. But even the best-designed roofs suffer from wear and tear. This is why routine maintenance and regular roof inspections are key.
Let’s take a look at the signs of roof ponding, its causes, and how to fix them.
Signs of roof ponding
Ponding occurs when water remains on a flat roof for more than 48 hours after rain or snowfall. The most obvious sign is the presence of puddles on the roof, but there are often more subtle signs that you should be on the lookout for, including:
- Water stains on the roof membrane (look for brown or black stains)
- Moss, algae, vegetation, or mold growth (look for green or black stains)
- Roof leaks, which may be caused by water overflowing over flashings or breaking down roofing materials
Causes of ponding
There are several reasons ponding occurs. While some issues can be easily addressed through routine maintenance, others can be quite complex and expensive to fix. The most common causes of roof ponding are:
- Clogged roof drain lines.
- A roof surface that isn’t tapered enough. Flat roof surfaces should be gently sloped to direct water and snowmelt towards drains.
- Low spots that have developed due to structural damage or compressed insulation.
- Structural damage caused by heavy HVAC equipment when the roof hasn’t been designed properly.
- Excessive foot traffic that has worn down the insulation.
- Not clearing excessive snowpack from the roof.
How to fix ponding
Water ponding on your flat roof can often be addressed through maintenance or easy repairs. Sometimes, however, a full roof replacement may be needed.
Here are some ways to fix the most common causes of roof ponding:
- Clear drain lines, gutters, downspouts, and scuppers to ensure that water and snow melt can drain effectively.
- Perform regular roof maintenance and inspections to stay ahead of potential drainage issues.
- Add new drains at low spots if the current drainage system isn’t handling all the runoff.
- Remove large amounts of accumulated snow from your roof as soon as safely possible.
- If ice is forming in drain lines, install electric heating cable to re-melt it.
- Ensure your flat roof has a minimum slope of 1/4 inch per foot (or about 2%). Tapered insulation can be installed on an existing roof to help achieve this slope.
- Install roof crickets, which are small wedge-shaped structures designed to push water away from low spots.
- Repair structural damage and/or replace sagging or wet insulation.
No matter what the cause of your roof ponding is, it’s important to have it repaired by a professional who understands flat roofs and their drainage systems. With years of experience in Wisconsin, New Roofs Inc. has the expertise to help ensure your flat roof performs as expected for years to come. Contact our service team to get started today.