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POOLING WATER ON FLAT ROOFS

There are numerous benefits to having a flat roof and one major downside.  Pooling water is a common problem with flat roofing as it does not drain water as effectively as pitched roofing which has a natural slope where the water can run off the roof.  Since flat roofs do not drain well they are prone to developing what is known as pooling or pooling water.  This refers to water that stands in a puddle on the roof for more than 48 hours at a time.

How To Stop Water Pooling on Flat Roof?

Pooling water might not be an immediate threat, but if it is allowed to persist over time, the danger grows and this water can begin to wear on the roofing membrane.  This reduces the membrane’s lifespan and 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 and it is very important that you address this issue right away.

WHAT CAN CAUSE PONDING?

• Insufficient drainage – A flat roof can pond if there is insufficient drainage, such as a blocked outlet or downpipe.

• Weight damage to the flat roof – A flat roof is not designed to withstand a large amount of weight.  If a heavy object is left on a flat roof, or if someone was to regularly walk on a flat roof (i.e., to use as a balcony) not designed for this purpose, the roof can begin to concave inward, trapping water and causing the roof to pond.

• A roof fixture – New roof fixtures placed into a flat roof such as a lantern or skylight can create gaps causing water to get trapped on a flat roof.

• Moss and waste – Moss and other waste such as dead leaves can hold water causing the rood to pond.  It is always important to remove waste and any excess moss.

• A change in materials – Originally, when a flat roof was lay, a roofer would use a material called limestone grit which gave a gravel appearance on the top of the flat roof.  As water would pool, the pool would lay invisible as the water would sit inside the gravel and remain undetected.  Since then this material is no longer used and more modern materials such as EPDM rubber and Modified Bitumen are becoming more popular.  These modern coverings tend to be smooth faced meaning pooling water that would previously be hidden by grit becomes much more obvious.

• Structural fatigue and settlement – Over time, roof joists and timber can settle and fatigue.  As this happens, the substrate sinks, creating a concave in the roof covering for water to collect and pool. As time goes on, the pooling and settlement go hand in hand and becomes a never-ending cycle which often results in full roof replacement.

STEPS TO TAKE

1. Flush Existing Drains

Drains can eventually become clogged with debris and in more extreme cases, these serious clogs can actually lead to standing water becoming a mainstay 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.  On its own, that debris seems harmless, but when it accumulates, it can lead to a variety of issues with your roof and the 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 working optimally.

2. Replace The Membrane

The membrane of your roof is the protective layer that keeps your roof safe from things like moisture getting into the building.  When that moisture builds up in the structure of your building, it can cause substantial structural damage.  A damaged membrane can happen for a variety of reasons, but pooling water is the most common one.  There are many membranes out there that are meant to withstand pooling water so if you find that you need to replace the membrane, you can benefit from a more effective, modern version.  You can also perform preventative maintenance to ensure that the membrane stands the test of time and bring in a roofing contractor to perform an inspection once or twice a year.

3. Fix Low Spots

They may be called flat roofs, but these are not entirely flat.  This is because there are subtle slopes in the surface of the roof that can 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.  One problem with these slopes can be low spots, where pooling can occur quite easily.  When that happens, the drains can clog with debris which leads to a buildup of water that can cause damage to the membrane and eventually cause leakage.  A professional roofing contractor will be able to fill in those low areas or you can have more drain lines added to the building.  If the current drainage system has issues with effectively removing water from your flat roof, adding additional drains is one of the most effective ways to take care of this issue, although it does add to your costs.  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

A pitch that was not properly designed or installed can be another problem for flat roofs and pooling water.  All roofs need some form of sloping to them, even if it is just subtle.  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.    If you need to make the investment, know what you are looking for and work with a professional roofing company.

5. Install Roof Crickets

When it comes to pooling on your flat roof, you might find that the water seems to mostly collect in specific areas.  These areas typically are 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.  You can also have serious issues with your roof if this insulation is insufficient.  Compressed insulation is generally caused by heavy roofing equipment that sits upon the insulation during the installation process.  Repeated treading over the roof area can also lead to indentations in your roof that can lead to pooling too. You need to ensure that the proper precautions are taken with the insulation and during any inspection processes.

WHAT IS THE RISK OF PUDDLES ON MY ROOF?

There is no actual risk of puddles on a roof top, these are very normal, however an extreme amount of water causing ponding on a roof top could be a risk.  Extreme ponding will only ever get worse until its too late.  Ongoing ponding will eventually damage the structure of a flat roof, eventually causing it to leak, by which point any repair would be too late, and a complete re-roof is required.

Conclusion

Keeping your roof working optimally is one of the most important aspects of owning that building and that roof is your toughest defense against the elements.  Preventative maintenance can keep your roof working efficiently.  Don’t let pooling water become an issue for your flat roof.