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Originally published in Interiors & Sources

01/24/2014

Protect Your Roof From Storm Damage

Know what to do before, during, and after an extreme weather event

By

 
Remove ice from rooftops quickly to avoid disaster.

Snow and ice must be removed from rooftops in a timely manner. They can clog drains or melt and leak into the assembly. To avoid these failures and even worse disasters like caved in assemblies, have a removal plan that includes where the snow should be dumped. Also ensure that only trained roof technicians are performing snow removal, as they are trained in how not to damage the surface.

Be Wary of Winter Weather

Use this checklist to help your roof endure the cold months.

  • Check exterior walls for leaks, stains, and cracks in brick and missing mortar. Seal these openings to make the building weather-tight.
  • Check the ceiling and interior walls for signs of leaks and staining. Before winter weather gets bad, seal as many roof leaks as possible. When the rooftop is covered with snow and ice, it becomes impossible to find them.
  • Check the roof deck and fascia/coping for any signs of deterioration. Check expansion joints for signs of excessive movement and splits, thin sections of membrane, and deteriorated caulking. Cold weather has a significant effect on loose mortar and composite building materials. They contract and may separate, creating entry points.
  • Check all penetrations on the roof, like pitch pockets, vent pipes, and pipe boots. Check flashings and joints for deterioration and voids.
  • Check and clear all gutters, downspouts, and scuppers. Clean out all drains and make sure they function properly. Check all strainers and clamping rings. Drainage problems in the winter months are a forerunner to future roof failure.
  • Check the field of the roof membrane and redistribute all ballasts across any bare spots. Check for tears and holes in the membrane and repair them promptly.
  • Remove all loose debris from the roof surface. Remove all unattached walk pads so they don't become an icy slip hazard as water freezes around and beneath them.
  • Remember that only trained roof technicians should remove snow from the rooftop. They are trained in how not to damage the roof surface.

Information courtesy of NATIONS ROOF LLC

When your site is susceptible to storms of any sort, don't throw caution to the wind. It's easy to forget your roof is up there – until it's caving in around you.

Whether you're facing wind, winter, or whatever the elements may bring, have a plan in place and make sure your building's roof is prepared for extreme weather. Human optimism makes us believe the worst won't come, and then it takes us by storm.

"We're seeing record temperatures, several inches of rain overnight, damaging winds, regional power failures, and building collapse from accumulated snow or plugged drains," says Richard L. Fricklas, former technical director emeritus of the Roofing Industry Educational Institute. "It's one thing to read about these things in the local newspaper – quite another when they affect your building and its occupants."

Successful handling of severe storms requires preparation, emergency response, and damage assessment. Take these steps to weather the risks of extreme conditions.

Plan for the Worst
Preparation revolves around personnel and procedures, but you should first assess the condition of your assets.

"The secret to successful roof management begins with an evaluation of existing roofs," Fricklas says. "This could be performed by skilled in-house staff or by an outside roof consulting firm."

Your existing maintenance program should already include semi-annual inspections. If it doesn't, be sure to perform walkthroughs prior to severe weather seasons.

"The best way to prepare is to maintain," says Steven L. McBride, president of Professional Roof Consultants (PRC). "Look for obvious signs of defect and make sure things are buttoned up."

Pay close attention to penetrations, flashings, and joints. Also verify that drains and screens are clear and functional. These areas are especially vulnerable during winter weather that poses the threat of moisture infiltration, but they also offer entry points for air in the event of extreme wind. .

The inspection of your roofs may reveal that your in-house maintenance staff is ill-prepared for a roofing emergency, Fricklas notes.

"Meet with key personnel and discuss what to do in the event of an emergency. At what point should snow removal tools be placed on the roof, and where should snow from the roof be dumped?" he adds. "If severe winds are predicted, address the placement of sandbags and where safety equipment is located."

Building personnel must have a comprehensive understanding of the building envelope. Communication between managers, staff, and contractors requires a common language. Fricklas recommends attending the programs offered by the RCI, an association of envelope consultants, architects, and engineers. Visit www.rci-online.org for subjects and schedules.

Before an event can occur, identify what exactly the manufacturer's warranty covers. Because extreme storm losses usually aren't included, make sure they are covered by your insurance provider.

"You can write a high wind warranty into the specification if you pay a premium," McBride explains. "If you're in a high-risk location, that's all the more reason to do so. Not everything is covered."

Respond to Avoid Disaster

What to Know about Wind

Although it's a common expression, roofs don't exactly "blow off." Familiarize yourself with other windstorm misconceptions and phenomena.

  • Factory Mutual (FM) Global, a testing laboratory that certifies materials, offers windstorm classification ratings such as I-60 and I-90. Many falsely believe the numbers refer to wind speed in miles per hour (mph). They actually apply to wind uplift pressures in pounds per square foot (psf).
  • Roof damage caused by wind occurs when air pressure below the roof assembly is greater than air pressure above the roof. As wind blows over the building, the pressure above the surface decreases, while simultaneously internal air pressure increases due to air infiltration. The result is a net upward force on the roofing system, referred to as wind uplift, bringing about the "blowing off" phenomenon.
  • A variety of factors affect how a building performs in high winds, including the building's overall height, the terrain surrounding the structure, and the type of roof deck used, among other criteria. FM Approvals account for all these considerations.

Information courtesy of FM GLOBAL

A windstorm can result in several kinds of damage. Protected membrane systems are vulnerable at the support board attachment to the structural deck, according to the RCI report Wind Uplift Resistance Evaluation of Commercial Roofs With and Without Add-ons.

In a lab setting with a pressure difference of 125 psf, metal plates and fasteners pulled through the support board, causing delamination of the membrane and air intrusion. PV modules and vegetated trays are also susceptible to damage and movement under these conditions, the report notes.

After a winter storm, snow must be removed in a timely manner to prevent it from clogging drains or melting and leaking into the assembly.

"One of our clients has a large canopy between the parking lot and facility. There was a major snowstorm, and everything became encapsulated in snow and ice. When it warmed up, the water had nowhere to go because the drain was encased," McBride explains. "Snow slid off the canopy onto the main ticket lobby roof and caved in part of the deck. It was a major event that impacted a lot of people."

Even extreme cold without precipitation poses threats. Another of PRC's clients didn't inspect the roof after a stretch of severe cold and didn't realize the roof had contracted to the point of cracking.

"When the cold weather went away, it started raining, and water just poured in," McBride explains. "The roof was split wide open like the Grand Canyon."

Reacting quickly becomes especially crucial if you can't personally make it to the site due to the nature of the storm.

"If your second in command points out that several ceiling panels have dropped out of the hung ceiling in the office, is he aware that it is probably due to the roof deck being deflected from ponded water? Does he know where the emergency roof gear is stashed?" Fricklas says. "Protective clothing and lighting should be available for the team to get up on the roof and open blocked drains before it collapses."

A computerized roof file will be handy when you need to know the location and warranty status of different roof systems. Make sure the system has a backup and that it can be accessed remotely.

"It's also wise to have maintenance contracts with local roofing contractors who offer 24/7 emergency roof service," Fricklas adds.

Assess and Repair Damage
After a storm, many facets of the roof system could be affected including its thermal performance, fire resistance, load and equipment carrying capacity, ability to drain and store water, and aesthetics.

But before calling in an expert, ask yourself if the damage observed is consistent with the intensity of the storm. Should the roof have performed better? It's likely that some damage is the result of an ongoing problem like poor drainage or inadequate ventilation. Answering these questions is helpful when dealing with warranties and insurance claims.

"The damage observed may often be present among several other construction, design, and maintenance issues," says David P. Amori, vice president of engineering at consulting firm EFI Global. "This convolution is the basis for discrepancies in the scope of repairs and cost."

An expert forensic evaluation determines if the roof is repairable or requires replacement, adds Amori. It begins with observing the interior upper floor for signs of water infiltration such as discoloration or delamination of finish materials. You may need to test the roof system or components to delineate whether the roof membrane, insulation, or any other parts of the assembly need to be removed.

In both PRC cases mentioned above, the remedies required replacement of only the impacted areas.

"We were able to get in touch with the manufacturer and explain that these defects should be covered by the warranty," McBride says. "We worked together. Manufacturers sometimes tell owners, 'Sorry, not included.' But that may not be acceptable. You have leverage."

Your roof can endure brutal impact from the elements. Don't relegate it out of sight and out of mind. "One of the most forgotten and neglected building systems also happens to be one of the most complicated," Amori says.

Avoiding costly remedies requires due diligence in preparation, response, and assessment. Perhaps most importantly, perform the majority of your due diligence during the calm before the storm.

"Be proactive with your roof and maintenance," McBride warns. "Whether you have been or not usually shows up after an extreme weather event."

 

Chris Curtland is assistant editor of BUILDINGS.

 


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