Buildings take a beating from Mother Nature so their occupants don’t have to. Sheltering people from shifting weather conditions is a building’s main purpose, and over time we’ve found ways to execute that goal and deliver safety and comfort with much greater effectiveness.
Improvements in durability and resistance to the elements have proven to be more important with each passing year. Severe weather events are becoming more common and more intense. It’s clear the buildings of tomorrow are going to have to be ready to endure difficult events and challenging conditions on a regular basis.
Roofs are often the target of the worst impacts of severe weather and other events. The choices made about the makeup and integrity of a low-slope commercial roof system at the beginning can determine how well it performs over time.
One way to beef up the protective power of a building’s roof is by incorporating a cover board as part of your roof assembly. Available in a multitude of different materials, including gypsum with coated glass mat, cover boards add an additional layer of protection and performance to a building’s roof.
A study conducted by FMI in May 2020 compared the performance of single-ply roof assemblies with and without a cover board. The research found that the use of a cover board on a single-ply membrane roof assembly increased the median life expectancy by four years. In addition, the use of a cover board reduced operation and maintenance costs by an average of $1.40 per square foot over a 20-year lifespan and increased the percentage of roof assemblies that met their full life expectancy.
Weather or Not
According to data from the National Oceanic and Atmospheric Administration’s National Centers for Environmental Information (NCEI), damage from severe storms is already on the rise. In 2018, hailstorm insured losses in the U.S. exceeded $10 billion for the 11th consecutive year.
When people think of storm damage, their minds often go to dramatic events, like tornadoes and hurricanes. But the fact is, hailstorms account for approximately 70 percent of average property losses for severe storms in the U.S., according to the NCEI report.
Today, 75 percent of U.S. cities experience at least one hailstorm each year. The damage caused is real and costly, leading FM Research and FM Global to establish a “Very Severe Hail Rating” for roofing products in 2019.
According to FM Approvals, testing to achieve the rating involves propelling 2-inch ice balls at the test samples at a velocity of 152 to 160 feet per second using compressed air to achieve an impact energy of 53 to 58 foot-pounds. This impact energy is the equivalent of a hailstone measuring up to 2 1/2 inches. There are roof assemblies that have received this rating and installing those can dramatically help resist damage from hail.
And hail isn’t the only building stressor that targets roofs. Durable, resilient roofs must also be able to cope with pressures from wind uplift, puncture and fire.
Roofing consultant Benchmark Inc. estimates that while a roof system represents only about 5 percent of initial building costs, the amount of money needed to repair roof issues related to storms and other problems over its life can represent as much as 77 percent of a building’s capital expenditures.
All of this adds up to the fact that any steps taken to improve roof resilience can deliver major benefits in terms of economics, maintenance and sustainability. When thinking holistically about the design of a building, the additional up-front investment required to incorporate a roof cover board as part of a roof system is relatively small when compared to the potential savings over the life of the roof.
“Cover boards are often used between roof membranes and rigid roof insulation in low-slope roof assemblies to enhance overall roof system performance,” explains Jason Wilen, AIA, CDT, RRO, in an article titled “Covering Your Options,” which appeared in Professional Roofing magazine, a publication of the National Roofing Contractors Association (NRCA). Wilen is NRCA’s director of technical services.
“As NRCA’s history of technical bulletins demonstrates, using cover boards with low-slope roof membranes is good roofing practice,” Wilen adds.
“[Cover boards] have a major niche in the market, and really should be used more than they are being used,” says Kevin Froeter, president of Sterling Commercial Roofing. “Twenty psi [pounds per square inch] is a typical insulation density, and 20 psi is nothing. [There are cover boards] that are 45 times stronger than what you’re going to have with insulation, so it’s a massive difference between the two. There are a lot of projects, especially those that have a lot of traffic on the roof, where a cover board is just absolutely necessary. A protection board gives you that added strength and dependability.”
Because roofs are out of sight for most occupants of a building, it’s easy to forget how much regular abuse they endure. Of course, hail and windborne debris present more extreme examples of ways a roof can be punctured or damaged, but even things related to regular operation and maintenance of a building can cause significant issues.
Dropped tools and heavy equipment used during repair or maintenance of a roof or rooftop equipment, like HVAC units, for example, can create holes, tears and, in other ways, compromise the performance of a roof. And in the holistic view of roof and building performance, there is no such thing as a small roof puncture. Any such damage can leave the building open to bulk water intrusion, airflow or moisture, any of which can damage the structure or impact the building’s performance.
As renewables and solar energy become increasingly popular for building owners, the risk to roofs increases and the importance of cover boards becomes even more crucial. The weight of photovoltaic arrays creates additional pressure on a roof that can be offset with the use of the right cover board system. The added puncture resistance of the cover board can also help maintain durability.
Codes, such as ASCE/SEI 7-16, “Minimum Design Loads and Associated Criteria for Buildings and Other Structures,” are becoming increasingly stringent about their requirements for structures designed to resist puncture and other damage. Installing the right roof cover board system can go a long way toward bringing a roof into compliance with codes and standards.
Severe storms present numerous threats to roofs and buildings as a whole. Wind itself can cause pressure through uplift forces. In the case of hurricanes and tornadoes, windborne debris can be an even bigger threat to the safety and integrity of a roof.
Cover boards add strength to the roof assembly and can mitigate potential damage caused by wind-uplift forces. The strength of the cover-board layer, much as in the case of roof-puncture protection discussed previously, offers additional shielding from flying objects that might be hurled around in the strong winds of a severe storm.
Noncombustible cover boards also offer a layer of protection against the possible spread of fire, either from inside or outside the building. Material choice in this respect is very important. While combustible materials can add fuel to a fire, noncombustible materials like gypsum can help limit the spread and suffocate flames.
Building owners, facility managers and architects are faced with a multitude of considerations and constraints in the design process. The impact of initial costs versus long-term costs must be weighed, as well as decisions about what investments provide the most impactful benefits for the building.
A strong, well-maintained roof will deliver many years of protection for a building. Considering the potential costs involved with major roof repairs or replacement, adding a cover board from the start can provide an extra layer of security and dramatically lower the risk of severe damage.
Owners want structures that will meet expectations for many years, and architects, engineers and contractors want to deliver on that desire. Enhancing the strength of a roof with a good cover board is a great way to minimize the potential for damage and maximize the long-term potential of a building.