What is Ponding Water on a Commercial Flat Roof?

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This picture illiterates ponding water on a commercial flat roof.

This picture illiterates ponding water on a commercial flat roof.

The National Roofing Contractors Association (NRCA) defines ponding water or standing water as water remaining on a flat roof (or low sloped roof) 48hrs after a rainstorm in July (taking into account evaporation).

The effect of ponding water on a roof system greatly depending on the roof type.

TPO/PVC roof systems properly install are not affected by ponding water. Most TPO/PVC manufacturer do not exclude ponding water from their warranties.

EPDM roof systems are susceptible to deterioration of seams and flashing which remain under ponding water conditions.

EPDM seam which completely failed under ponding water conditions.

Modified and asphalt BUR roofs do not perform well in ponding water conditions. Most manufacturers with exclude ponding from their warranties.

No matter the roofing system, it is good to eliminate ponding water on your roof whenever possible. There are two major reasons for eliminating ponding water from your roof:

  1. Weight load – significant ponding water weighs a lot, which can be detrimental to your roof structure and the building’s occupants’ safety.
  2. When there is a deficiency in your roof in a ponding water area, the roof will continue to leak even after the rain stops. This will cause more damage to your roof, your building, and the contents of your facility. Possibly slowing down and or halting your production for a more extended period of time.

What can be done about ponding water?

When your budget allows, consider having additional drains or scuppers installed. When re-roofing a section of the roof, consider a tapered insulation system designed to slope water to the drains or scuppers. Drain sumps and cricket can also be helpful.

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One thing you can do to prevent roof leaks?

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Make sure your roof drains are free-flowing.

Clean all roof debris that could clog your drains.

Water will always travel the path of least resistance.

If the drains are clogged, water will find another way into the building (a slice, a hole, or even a bad seam or flashing).

The quicker water drains from your roof, the less time it has to find an imperfection to leak thru.

Your drains, along with any roof debris, should be cleaned a minimum of twice a year.

This can be done on its own or as part of a preventative maintenance program.

If you would like to learn more about a preventative maintenance program and how it can benefit you and your building, contact us.

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Should you remove snow from your flat roof? Or should you hire a professional?

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There are several things you should consider:

1)    Safety and fall protection should be your number one concern any time you access your roof. Most flat roofs become incredibly slippery when there is water, frost, or snow present. Injuries and possible death can result from slips and falls. Follow all OSHA regulations when accessing your roof.

2)     Do you really need to remove the snow?  how much snow load can your roof safely handle? Your building’s snow load capacity all depends on how much snow and how heavy it is. It also depends on the condition of your existing structure. You should consult a certified structural engineer.

3)    Is your roof leaking when snow and Ice are present? Modern roof systems with the exception of low sloped metal roofs are designed to be water-tight when covered with snow and Ice. If you are having leaks, one of two things are occurring,  The first snow is built up over the height of the flashings and is getting in a unit, window, or a crack in the wall, etc (in this case some removal of snow may be in order). The second reason is a deficiency in your roof system, that needs to be addressed by a professional roofing contractor.

4)    Will you damage your roof while removing snow? Punctures and tears are very common when removing ice and snow. Do you have the capacity to fix holes and tears before they leak? Will you even realize you damaged your roof? Most holes and tears are tiny. Most roofing manufacturer’s warranties do not cover punctures or tears caused by snow removal or other work on the roof.

Consider hiring a professional roofing contractor who specializes in flat roofs to remove your snow.

It is true; a professional roofing contractor will be more expensive upfront to hire, however:

A professional roofing contractor will have the correct insurance coverage.

A professional roofing contractor will have a proper fall protection plan and equipment.

A professional roofing contractor will have the experience and equipment to remove the snow while minimizing damage to the roof safely.

A professional roofing contractor will have the material and know-how to find and repair any damage during the snow removal process.

Hiring a professional roofing contractor to remove your snow safely will save you the cost of roof repairs and headaches in the long run.  


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