It’s no secret that severe weather events are on the rise throughout the United States. According to the National Oceanic and Atmospheric Administration’s (NOAA’s) National Climatic Data Center, approximately 300 “billion-dollar extreme weather events” have plagued the country in the past 25 years. 

What makes a “billion-dollar” event? NOAA calculates the total direct costs of the damage resulting from a storm. This includes physical damage to residential, commercial and government buildings, as well as harm to material assets within buildings, public infrastructure, vehicles and boats, offshore energy platforms and agricultural assets. Finally, the costs of losses from business interruptions, disaster restoration and wildfire suppression costs are also included. 

Most of these events are classified as severe storms and tropical cyclones, including hurricanes. While these types of storms may wreak havoc on any property, the long-term effects of severe weather damage can be especially catastrophic for commercial buildings and the businesses they house.

One opportunity to minimize risk? Your roof. It’s a critical part of the building envelope that is susceptible to major damage from gale-force winds, torrential downpours and severe hail. Among common commercial roof systems, some provide elevated performance characteristics that could enable them to resist storm damage more effectively than others.

In this article, we’ll explore the stakes of severe weather events for commercial facilities, common points of roof failure under extreme weather conditions, and the specific performance characteristics that could enable some roof systems to outperform others when Mother Nature’s worst strikes. Let’s explore:

Severe Weather: What’s at Stake for Commercial Facilities

Extreme weather can have wide-ranging impacts on commercial buildings and industrial facilities. If the roof system is compromised, rainwater can infiltrate the building, leading to leaks and flooding inside the facility. 

When this happens, production may grind to a halt, and downtime can be extremely costly due to lost production, product spoilage or water damage to critical infrastructure. Further, prolonged flooding can lead to mold growth, contamination and indoor air quality issues, as well as potential electrical hazards, all of which can put workers health and safety at risk. In addition, building owners may face higher insurance premiums, repair and replacement costs, and other financial burdens that threaten their bottom line. 

Preventing these consequences starts with understanding how and where severe weather can impact your roof system.

How and Why Roofs May Fail in Severe Conditions

When a major storm strikes, flying debris is one of the greatest threats, as it can tear or puncture the roof membrane. Strong winds can send materials through the air and toward your facility, and materials or debris on your rooftop can become threats. Consequences may include roof failure and significant leaks. 

High winds exert direct pressure as well. Windward perimeters and corners of the roof are typically the first areas to fail under high wind conditions. When wind pulls on the edge details, portions of the membrane that are not properly installed or maintained may start to peel back and pull up, potentially leading to total failure. Elsewhere, any sections of the roof where equipment penetrates the membrane can be susceptible to the same type of damage. Consider your vent systems, exhaust fans, HVAC equipment or any other units connected to interior operations. 

TPO failure. Image courtesy of FiberTite

Other severe weather conditions can threaten your operational security, too. Very Severe Hail, classified as hailstones that exceed 2 inches in diameter, can cause major damage to roof membranes that do not exhibit strong puncture resistance.

To reduce the risks, facilities should proactively evaluate the health and condition of their roof systems. Best practices include: 

• Inspecting the roof prior to storm season
• Removing debris from the rooftop 
• Performing preventive maintenance and inspections 

Such evaluations may uncover issues that elevate your risk under storm conditions, including improper fastener installation or adhesion failure, loose or disconnected metal edges, open seams and other addressable issues.

Tear and Puncture Resistance: Comparing Common Roof Types

Available roof membranes vary in how well they withstand severe weather conditions. Being aware of these differences can help you understand or improve the resilience of your facilities. 

Commercial low-slope roofs often include one of four single-ply membrane types: thermoplastic polyolefin (TPO), polyvinyl chloride (PVC), ethylene propylene diene monomer (EPDM) and ketone ethylene ester (KEE). TPO is the most common membrane used in the United States, specified due to its lower upfront cost. 

However, upfront cost does not make up the total cost of a commercial roof system throughout its service life. Long-term performance under severe weather conditions should be considered. For example, KEE-based membranes meeting relevant ASTM testing standards have demonstrated exceptional puncture and tear resistance compared to TPO, PVC and EPDM membranes. Why? The ASTM 6754 standard requires KEE membrane construction to include a strong fiber reinforcement layer as well as a minimum of 50% KEE polymer. Other membranes are held to performance requirements of their respective ASTM standards, which can result in significantly lower puncture and tear resistance properties.  

These attributes can make a difference under severe weather conditions. A KEE membrane would be more capable of resisting puncture and abrasion from flying debris or foreign objects striking or moving across the roof. KEE membranes could also be less likely to tear or rip at the seams or points of fastening along the roof’s perimeter and corners, reducing the chance for wind uplift and subsequent roof failure. 

Applying Relevant Codes and Standards

Building owners can consult relevant codes and standards for guidance. The FM Global 1-90 standard (FM 1-90), for example, is a widely recognized benchmark for wind uplift resistance in commercial roof systems. This rating is often cited in local regulations, manufacturer specifications and insurance requirements. Systems that meet this standard can generally be trusted to deliver good performance in extreme weather conditions. 

Some parts of the country require elevated wind performance. The Florida Building Code (FBC) mandates all commercial roof systems to be capable of withstanding specific wind pressures based on the building's location, height and exposure category. Such roofing materials and assemblies must undergo rigorous testing to verify their wind uplift resistance per required standards, including UL 580 and UL 1897, which evaluate uplift resistance, and FM 4474, which assesses the roof assembly performance under simulated wind conditions. 

While various roof membrane types can meet these requirements, selecting a high-performance system tailored to your building’s vulnerabilities provides an extra layer of assurance.

Today’s building envelopes must demonstrate storm readiness in the face of increasing severe weather. Your choice of roof system can make a major impact—those with exceptional durability and puncture resistance are better equipped to withstand the threats associated with major storms. Your operational security may depend on making the right choice.