Despite the advantages of having a flat roof, there is one major downside. Pooling water is a common problem with flat roofing because it does not drain water as effectively as sloped roofing. Not being able to drain water means there is a risk for pooling. This refers to water that stands in a puddle on the roof for more than 48 hours at a time.

How To Stop Water Accumulating On Flat Roof

Pooling water might not be an immediate threat, but if it is allowed to persist over time, the danger grows. This accumulated water can begin to wear on the roofing membrane, reducing the membrane’s lifespan. This can lead to things like leaks which can cause serious problems for the rest of the building. Thankfully, there are a few tactics that you can employ to resolve those pooling water issues. Most importantly, these should be done right away.

1. Flush Existing Drains

Drains can eventually become clogged with debris which can actually lead to standing water on your roof. To prevent that buildup of debris, try removing sticks, leaves, and any other rooftop debris from the drainage system of your building. Debris on its own is harmless, but when it accumulates it can lead to a variety of issues for your roof drainage system. Regularly cleaning your drains or hiring a professional roofing service to come to do this once or twice per year is the best way to keep your drainage system clean and reduce the risk of pooling water.

2. Replace The Membrane

The membrane of your roof is the protective layer that keeps your roof safe from things like moisture. When that moisture builds up in the structure of your building, it can cause serious structural damage. Pooling water is one of the most common reasons for a damaged membrane. Many membranes are designed to withstand pooling water so if you find that you need to replace the membrane, you are better off investing in one of these more effective, modern versions. Regular preventative maintenance should also be done to ensure that the membrane stands the test of time and this should involve having a roofing contractor perform an inspection once or twice a year.

3. Fix Low Spots

Despite their name, flat roofing is not entirely flat. There are subtle slopes in the surface of the roof that come as a result of the installation process, weak spots in the roof, or a particular focus of debris or precipitation. These slopes are meant to facilitate drainage to help reduce pooling water on your roof. A common problem with these slopes can be low spots, where pooling can occur quite easily. When that happens, the drains can clog with debris leading to a buildup of water that can cause damage to the membrane and leaks. A professional roofing contractor will be able to fill in those low areas or you can have more drain lines added to the building. Most professional roofing contractors can install extra drain lines or even widen the existing drains in order to direct that excess water away from the rooftop.

4. Re-pitch The Rooftop

The pitch that was not properly designed or installed can be another contributing factor for pooling water. All roofs need some form of slope and without the right amount of sloping, the water won’t be able to drain and will more often than not lead to additional pooling. The process of re-pitching the roof can be costly, but it might also be the only solution if you find that you are consistently having pooling issues.

5. Install Roof Crickets

You might find that the water seems to mostly collect in specific areas, specifically near chimneys or around large vents. The best way to handle water pooling in these areas is to install roof crickets in those areas. Crickets are rigid structures designed to divert water around roofing obstructions like chimneys, that have a naturally difficult time draining water on their own.

6. Compress Insulation

Another problem that can lead to pooling water is compressed insulation. Compressed insulation is generally caused by heavy roofing equipment and repeated treading over the roof area that can lead to indentations in your roof. These dents are perfect for collecting water, so you need to ensure that the proper precautions are taken with the insulation and during any inspection processes.


Keeping your commercial roof working optimally is one of the most important aspects of owning that building. Preventative maintenance can keep your roof working efficiently. Pooling water is a common problem for flat roofing but you can prevent it from becoming a serious issue. Use these tips and call us if you have any concerns about getting rid of pooling water.

For any questions or to schedule a roof inspection, contact us today!