How ice, snow and rain impact your roof and what you can do about it
By Janelle Penny –
Plunging temperatures, slippery surfaces and extra precipitation combine to wreak havoc on roofs, from overloading drains to straining roofing materials through expansion and contraction. But a little planning can minimize the impact on your roof and ensure you’re prepared for the worst-case scenario. Protect your roof from winter’s worst with these tips.
Why Winter Can Wreck Roofs
The temperature changes and precipitation winter brings can cause a number of problems on your roof. Changing temperatures can be especially tough on single-ply membranes due to a phenomenon called supercooling, in which the membrane hovers around 5-10 degrees F. colder than the ambient air temperature, explains Tom Gernetzke, Project Manager for Facility Engineering, Inc., and a Past President and Fellow of RCI.
“Supercooling is particularly notable on clear moonlit nights where thermal radiation is emitted into space quickly,” Gernetzke says. “That 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 on many roofing systems can be 130 degrees F. or more, especially if you go from a shadow line to an area that’s in the sun or an area that’s not covered by snow and ice to one that is. That can really strain some membranes.”
Adam Herring, Senior Project Manager at Highland Commercial Roofing, a provider of seamless cool roofs, recommends having a plumber check your drains while the weather is clear to ensure that rain, melting snow and ice can make it through, particularly if your building is in an area that receives considerable precipitation in winter. However, drain conditions can change quickly throughout the season, Gernetzke adds, so keep an eye on them to make sure you don’t end up with ponding water or excess weight on the roof. Drainage issues can surface under any of these conditions and can quickly become an emergency:
Frozen or clogged drains and scuppers: Roofing systems are intended to have good drainage at all times to get water off of the roof as fast as possible, Gernetzke says. Don’t let drains, gutters or scuppers stay frozen for long.
Trapped melt water: Water that becomes trapped under a layer of refreezing ice or snow can add thousands of pounds of extra weight, Gernetzke explains. “Most buildings that comply with building code are safe from having to worry about too much snow and ice stressing the building, but it certainly can happen,” Gernetzke adds. “A few years ago on the East Coast, there was significant structural collapse from the tremendous amounts of snow and ice the area received, which overstressed quite a few structures. A lot of the overload issues were the direct result of a large snow event of 12 to 36 inches of snow, followed by a warmup and then a rain event. What typically happens with those conditions is that the rain will melt some of the snow and compact it, but the drainage components are still frozen and don’t allow all of the water to drain off, so multiple events compound to create a bad situation.”
Ice damming: This occurs when snow builds up on the roof and then partially melts on a warmer day. If temperatures cool rapidly, the melted water that has migrated to the drainage areas freezes, forming a dam that holds back water and creating a ponding water area behind the ice dam, Herring explains. “Even with barriers installed at the edges of the roof, your roof system may not be able to handle the hydrostatic pressure from the water that dams up,” Gernetzke says.
Steep slope roofs are also at risk of ice and snow shear, where packed ice or snow slide down the sloped roof and shear off flashings, seams, joints, penetrations and even retention fencing.
How to Prepare for Winter
Getting your roof ready for winter starts with a comprehensive inspection while the weather is still clear, typically in fall. (See “Roof Inspection Checklist” above for sample inspection procedures.)
“The most common areas of damage are at drainage points and any penetrations,” Herring explains. “The perimeter at the walls is important, and inspect any high-traffic areas as well. Some building owners perform these in-house, but if you plan to hire someone else to do the inspection, take into consideration that there could be long lead times as you get closer to winter and plan accordingly.”
Look for damage caused by bird species, especially around HVAC equipment or anywhere else water could collect, as they tend to gather around water, Herring notes. During the inspection, remove any debris, leaves, branches or refuse that could catch a ride on some heavy rainfall and end up in the drain.
“Contact your roofing representative to make sure how you intend to clean the roof is safe for that roofing system,” adds Herring. “You may not be able to power-wash in some circumstances, for example. Typically, a soft-bristled broom or leaf blowing is probably OK, but you want to make sure you don’t damage the roofing system when you’re trying to clean it.”
This inspection is part of a two-pronged approach to roof care. Every FM whose duties include roof maintenance should have both a proactive and reactive plan, Herring recommends: “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.”
Signs Your Roof Is Developing a Problem
Periodically check in on your roof to see how it’s handling the winter. Some issues can be spotted from the ground, Herring notes. For instance, icicles at the gutter are a signal that it’s full of ice and you likely have an ice dam on your hands. Also check for buildup if you had a relatively warm day followed by a cold one, as the conditions will be favorable for damming.
“This can only be accomplished if you make sure all of your access points to the roof are maintained. You wouldn’t want a penthouse door with a couple of feet of snow blocking it from opening or a huge pile of snow covering your access ladder,” Herring says.
A building with a steep slope and an attic space should be checked to ensure all insulation is still in place, vent pipes are connected and interior doors leading to attic spaces are sealed.
“Many times we’ve found items like an HVAC tech performing work on a unit in a roof attic who then couldn’t find a way to get to the attic, didn’t know who to talk to, cut a hole in the separation wall between an attic and a finished space, got into the attic and then didn’t tell anyone and left, leaving a 3- by 5-foot hole in the drywall that was pumping hot air into the attic space,” Gernetzke says. “It resulted in pretty significant ice damming until that hole was patched up.”
A frosty day can actually make it easier to find leaks or other roof anomalies, a trick Gernetzke refers to as the “poor man’s infrared.” Try doing your inspections early in the morning while there’s still frost on the roof – the light dusting can help highlight areas where temperature or other properties are different.
“You can also see areas where you might have leaks if you find water on a roof assembly,” Gernetzke adds. “If you see water on a roof assembly that also has snow on it, that area is warmer than the surrounding areas and will melt frost and snow faster. Keep in mind that a light dusting of frost, ice or snow on the roof can be very slippery, so if you do have to walk on the roof while you’re doing this, please be very careful.”
The simple act of snow removal itself can also lead to damage, Gernetzke adds, so unless you’re looking at ice damming, serious overload or another potential emergency, it may be best to leave the snow and ice on the roof and just keep an eye on it for issues that could develop later.
“If you’re confident that the roof will hold the snow you have, I usually recommend not removing it unless you have a reason to believe you need to,” Gernetzke says. “Snow removal operations can wreak havoc on a roofing system, particularly low-slope roofs, where if you do puncture a membrane you can let in hundreds, if not thousands, of gallons of water into the roof. It’s extra difficult to repair those once the damage has been done.”
How to Handle Emergencies
If your roof does develop a problem that can’t wait until spring, don’t panic – there are a few stopgap measures you can try while you’re waiting for a contractor to arrive. Many mid-winter emergency repairs are solely focused on stopping leaks and keeping water out of the building, Gernetzke notes. For example, if you have an ice dam building up on a steep-slope roof, Gernetzke recommends a couple of inexpensive tricks to melt channels in the ice for the water to drain through – installing temporary heat cabling or filling a tube sock with ice melt.
“If you just put ice melt on the roof by itself, it runs off of the roof when the water starts to run,” Gernetzke notes. “Another trick is to chop channels through the ice, but you’ve got to be really careful doing this. Use plastic tools or equipment – that can be hard, especially if you’re chopping through 12 to 16 inches of ice dam, but you could do some damage otherwise. It’s also important when you’re removing dams or snow and ice from any roof that you know what’s below so that you don’t crush someone, damage cars or impact the landscaping. Please have a professional do this and make sure you have the proper insurance to cover this work – it’s very dangerous and it’s easy to damage things below the roof.”
If a leak develops, cat litter that contains bentonite clay can soak up a considerable amount of water and keep it from getting into a puncture, Gernetzke notes. Herring recommends keeping some tarps on hand for both the exterior and interior – the latter has a funnel and hose attached to redirect water into an indoor drain or container to prevent damage in critical areas.
“Every roofing contractor will have lead time to respond to repairs, and sometimes there’s nothing you can do but weather the storm until someone can stop by,” Herring adds. “Have a plan, materials and training in place to deal with an emergency leak in-house.”
Plan for Next Year
After winter passes, conduct another inspection to find tears, rips, splits and other damage and fix these issues as needed. Record your findings and keep them in a roofing file alongside warranty documents, invoices, repair and maintenance records and other roof documentation. The file should also include an up-to-date list of emergency contacts, Herring adds.
“Know who to call in case of an emergency and get all the training you can on proper roof maintenance and emergency repairs,” Herring says. “Don’t be afraid to admit that you need some training on roofing. Reach out – there are a lot of people out there who are willing to help.”
Janelle Penny firstname.lastname@example.org is senior editor of BUILDINGS.