Metal roofing systems are tested by third-party laboratories to several performance standards, ensuring they can withstand the damaging effects of powerful storms, wildfires and more.
Like all other parts of the built environment, roofs are subject to a wide range of building code requirements. Depending on a project’s occupancy type, size and location, these requirements may include specific wind-resistance or hail- and impact-resistance ratings. In addition, certain counties, states and departments of insurance may have additional standards that roofing materials must meet to be approved for use.
Metal roofing systems are tested by third-party laboratories to several performance standards, ensuring they can withstand the damaging effects of powerful storms, wildfires and more. Knowing the performance capabilities of a metal roof, distributors, fabricators and installers can confidently recommend appropriate products and systems that meet the code requirements for a project.
Roofing systems are classified on a tiered system (from A to C) according to UL 790 or ASTM E108 standards. Metal roofs, whether galvanized steel, aluminum or copper, receive the highest class rating, Class A, according to UL 790 standards. Materials with a Class A fire rating have the lowest flame spread index and will not add fuel to a fire, making them ideal for wildfire-prone environments. For metal roof panels, the most critical component in the context of fire resistance is the roofing substrate—its profile and gauge do not significantly alter the rating classification.
In addition to UL 790, some metal roof substrates are certified to UL 263 standards. These testing protocols simulate common fire conditions that occur in commercial buildings, and therefore provide a closer measure of performance for these occupancies than class ratings alone.
In addition to enhanced fire resistance, roofs should also withstand high wind pressure—something that is particularly critical in locations prone to hurricane-level winds. Unlike fire ratings, there are multiple testing standards that quantify wind resistance ratings for roofs, including UL 580 Wind Uplift, TAS 125 Wind Uplift, UL 1897 Extended Phase Wind Uplift, ASTM E1592 Uniform Static Pressure Uplift and ASTM E1680 Air Infiltration.
If a roofing system passes the minimum standard for the majority of these tests, it also receives data that quantifies the maximum pressure withstood (in pounds per square foot [psf]) for no less than one minute.
An exception to the above, UL 580 ranks roofing assemblies by class. Drexel Metals’ roofing systems have achieved class 90 ratings, the highest rating possible. This means that they are designed to withstand the maximum static and oscillating uplift pressures. In the field, high winds often bring rain and hail, so it is important that roofs also pass water infiltration and impact resistance testing standards.
Hail and falling debris can wreak havoc on a roof. Damage caused by impact might be easy to spot—or it may go unnoticed. When damage is hidden from plain view, it might only become apparent once the roof starts leaking, which can lead to other costly building damages. A roofing system that protects against hail, falling tree limbs and wind-driven missiles helps ensure a long service life for the roof itself and the building it covers.
It is important to note that there are different testing standards for hail and impact. For hail, roofs are subjected to UL 2218, which tests their protective capabilities and ranks them on a class system (from one to four). Metal roofs rank highest with a class four rating, which ensures the maximum protection from hail. While this is a key metric, it is also important to consider how a system’s paint finish can resist hail and impact to help keep the roofing substrate in pristine condition.
ASTM E1886 measures a roof’s ability to resist impact from missiles, including falling tree limbs and other wind-driven debris, while also subjecting the system to cyclical static pressure differentials. Like hail protection, this helps ensure a roof can withstand potential damage and minimizes associated risks (including leaks) during and after conditions that model windstorm events.
Metal roofing systems provide some of the highest ratings possible for fire, wind, rain, hail and impact protection. As such, they ensure a long lifespan—often two to three times longer than asphalt shingle roofs and without the additional weight of concrete or ceramic roof tiles.
Have additional questions? Take this AIA-accredited course from Drexel Metals for an in-depth look at each test that is performed on a metal roof system: https://ccm.buildingmedia.com/drexel/courses/drexel/understanding-metal-roofing-engineering-and-testing/.
