When it comes to protecting the flat or low slope roof over your place of business from the threats of a northeast winter – plunging temperatures, the expansion and contraction of thawing and freezing, or the stress of snow loads – a little planning, some proactive maintenance and well-timed inspections can minimize the effects of Winter Weather on Commercial Membrane Roofs. The first step in preventing winter weather damage to an EPDM, PVC or TPO membrane roof is to understand the cause.

Why is Winter so Hard on Membrane Roofs

So far during the Winter of 2020, temperatures here in Connecticut have climbed to the low 70s and then plummeted to the low teens, all within the same week. Dramatic changes like this can be especially tough on single-ply membrane roofs. This can be exacerbated by a phenomenon called “Supercooling”, where the membrane roof temperature is colder than the ambient air temperature.

Just one Frozen Roof Drain can make for a costly winter storm season.

Tom Gernetzke, of Building Envelope Consultants Group, LLC, explains: Supercooling is particularly notable on clear moonlit nights where thermal radiation is emitted into space quickly which subjects those membranes to much colder temperatures, and when it warms up in the daylight or part of it is next to a warmer building component, the forces of expansion and contraction can be even greater. The temperature differential can be 130 degrees or more, especially if you go from a shadow line to an area that’s in the sun or an area not covered by snow and ice to one that is.

A related complication is pooled water caused by clogged drainage systems, which can be exacerbated by these dramatic changes in temperature. While it’s always wise to check drains while the weather is good to ensure rain, snow melt and ice can make it through – that doesn’t necessarily mean you are in the clear. Again, Tom Gernetzke offers some perspective: No matter how much you plan, something will eventually go wrong. Have a vendor on file who can respond to emergency repairs and have some materials on hand you can apply in wet conditions. Find out from your roofing rep whether they offer an emergency repair training seminar.

Potential Water Drainage Issues

Beyond the impact of cold or fluctuating temperatures and potential damage from heavy snowfall accumulation, unchecked roof drainage issues are another concern related to Winter Weather on Commercial Membrane Roofs as they can threaten the integrity and watertightness of commercial flat roofs. Three scenarios we’ve seen lead to catastrophic results include:

  1. Clogged or frozen drains and scuppers:  When functioning properly, the drainage systems in good roofing designs shed water as efficiently as possible. When drains, gutters or scuppers become clogged with debris, ice forms and they become frozen – slowing or stopping the drainage rate.
  2. Trapped melt water: Membrane roofs are designed to move water; when snow melt becomes trapped due to snowfall or ice, it can add significant weight the roof was not designed to support.
  3. Ice damming: When snow builds up on the roof and partially melts during warmer dayparts, melt water travels to the drainage system on the roof. As temperatures cool – especially when cooling happens rapidly – the melted water in the drainage areas will freeze and form a dam. Melting and Freezing cycles makes the dam bigger and bigger.

Each of these aforementioned scenarios can create circumstances where water is not being moving off your roof and, more concerning, additional precipitation (snow, sleet or rain) can compound roof weight overload issues.

Indications of a Potential Roof Overload


Understanding the signals of a potential Roof Collapse is Critical.

In all likelihood, your commercial flat roof or low slope roof has been designed to handle the snow, ice and rain that typically accompanies winter weather on commercial membrane roofs here in Southern New England. And while they are bothersome, the minor leaks that crop up during a winter on an older membrane roof are merely an inconvenience if dealt with properly.

However, a roof overload caused by heavy snow accumulation or improper drainage can lead to catastrophic ramifications so it’s crucial to know the signals of a roof overload in case it happens to your building. Every winter, you will read about or see televised reports of a roof caving in due to heavy snow loads. FEMA has put out a guide on how to detect and then deal with some of these issues. If you observe any of the following, you should evacuate the building immediately and then seek professional inspection:

  • Sagging ceiling tiles or boards
  • Ceiling boards falling out of the ceiling grid
  • Sagging sprinkler lines and heads; especially if they hang below suspended ceilings
  • Popping, cracking or creaking noises
  • Sagging roof members, including metal decking or plywood sheathing
  • Doors and windows that suddenly become difficult to open or close
  • Cracked or split wood members
  • Cracks in walls or masonry
  • Severe roof leaks
  • Excessive accumulation of water at non-drainage locations (especially on low-slope roofs)

Preparing and Protecting your Commercial Roof from Winter

Now that you understand some of the issues of Winter Weather on Commercial Membrane Roofs, here are some steps you can take to diminish the likelihood of these problems.

First, have an experienced commercial membrane-roof installer inspect your roofing system prior to the onset of winter. If you haven’t done this and would like our help, please contact us. Note that our next blog post will be about what we look for in a comprehensive inspection.

Ice Dam on an EPDM Roof

If left unchecked, Ice Dams on Flat Roofs can lead to ponding and leaks (or worse).

Next, check your roof periodically during the winter months. Begin with an inspection from the ground; look for damage to gutters or extensive icicles hanging over the sides of gutters or roof edge, which could signal the presence of an ice dam. Make a note to check this especially if you have warm days followed by cold days, which can create damming in the right (or wrong!) circumstances.

After this, head up onto your roof and look for areas of pooling water around drains or gutters. If it’s safe, remove any debris which has built up and is causing a blockage. Check for any split seams especially around protrusions.  A pro-tip – make sure you that roof hatchways are opening freely and unimpeded by rust or corrosion as this could compound the difficulty in opening these under the weight of snow.

Speaking of heavy snow, be careful if you decide to remove it – membrane roofs can be susceptible to puncture and tears in snow removal situations which will create leaks. Removing snow from a commercial building must be done properly and safely for both the crew and the building. We have experience in this regard so contact us if you have questions. However, given the inherent dangers and the fact that most roofs are designed to handle and get rid of snow loads, it might be best to leave typical amounts of snow on your roof.

Dealing with Emergencies

The first thing to do in an emergency is to ascertain whether it’s safe for the building to be inhabited. If the concern is a leak, that’s probably not a cause for panic. But if you observe any of the signs of an overloaded roof (listed above), err on the side of caution and get people out of the building.

If someone on your staff – a facilities or operations manager, for example – is the first line of defense in a winter roof emergency, make sure they are trained in understanding how much weight your roof can handle, how much snow or unremoved snow melt weighs and, most importantly, the signs of a compromised roof (some of which are listed above). This is no time to learn on the job.

Another important consideration in emergency situations is pre-planning and forethought. Part of your pre-winter plan should be to evaluate a few roofing contractors who you might call in the case of a leak or failure so you have an understanding of their abilities. And so your name is familiar to them in the event you need help – if your building is experiencing a heavy snow load, the chances that other buildings in the area are experiencing the same thing are high. So having a roofer remember you might move you up in the cue.

Finally, if you have questions or concerns regarding the upkeep of your membrane roof this winter, contact us. We have 50 years of experience inspecting and protecting Commercial Membrane Roofs from the damage which can be dealt by a Connecticut winter.

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