Key Takeaways:
One quiet stretch of weather has a way of erasing the lessons of a violent one. The National Hurricane Center calls it hurricane amnesia: the false comfort that sets in after a few years without a major landfall. That comfort gets expensive fast, and it reaches well beyond the coast. Straight-line winds, torrential rain and hail test commercial roofs across the country every year, and one calm season does nothing to change the long-term trend toward more frequent and severe weather. For facility managers, that trend is the planning assumption that matters.
The roofing assembly is the building's first line of defense against all three threats, and it is usually where damage starts. Wind pulls at edges and corners. Wind-driven rain probes every seam, flashing and penetration. Hail and flying debris punch at the membrane surface. EPDM, the rubber membrane that has likely protected low-slope commercial buildings for more than 50 years, holds up well against this battering when it is designed, installed and maintained correctly. But no roof survives a storm on reputation alone.
Good preparation starts with understanding how your roof was built to perform. Building codes set much of that baseline, and for low slope roofing assemblies the key provisions sit in Chapter 15 of the International Building Code (IBC). It helps to remember what codes are: a floor, not a ceiling. They define the minimum a roof must meet, not the level of performance an owner should expect in a severe-weather region.
Wind resistance is the piece that matters most in a storm. The IBC requires roof systems to be designed for the uplift pressures they will actually face, calculated under the ASCE 7 load standard for three zones: the field, the perimeter and the corners. Perimeters and corners take the highest loads, which is why they fail first, and height only compounds the problem. The corner of a roof 30 feet above grade might see roughly 62 pounds per square foot (psf) of uplift, while the same roof at 200 feet can approach 130 psf. Assemblies prove they can handle those loads through testing under FM 4474, UL 580 or UL 1897, the source of ratings such as FM 1-60 or FM 1-90, and the metal edge is covered separately under ANSI/SPRI ES-1, since a roofing assembly that holds in the field is worthless if the edge peels away first.
Recent code cycles have gone further. Updates to the 2021 IBC strengthened edge attachment and added rules for rooftop aggregate and ballast. They also began requiring construction drawings to show the wind-uplift pressure zones themselves. How the membrane is attached matters just as much as the numbers. An adhered EPDM system, for example, bonds the membrane across the entire deck and spreads uplift forces evenly, while ballasted systems that rely on loose aggregate are restricted in hurricane-prone regions. If you do not know your roof's assembly method, membrane thickness or uplift rating, find out before the season.
The roofs that fail in a storm are usually the ones carrying problems that were visible months earlier. A pre-season inspection by a qualified professional is the single most valuable thing an owner can do, and it works best as an independent check rather than a rubber stamp.
Focus that inspection where storms cause damage. Check edge metal, termination bars and flashing for any looseness or lifting, since these are the first components that wind attacks. Watch flashing height too, because terminations that sit low above the field are more vulnerable to wind-driven rain. Then inspect the penetrations. Vents, drains, exhaust fans and rooftop units all disrupt the membrane, and each seal is a potential entry point.
Water management deserves equal weight. Codes require low-slope roof systems to drain, generally at a minimum slope of one-quarter inch per foot, with no ponding 48 hours after a rain, and they require secondary or emergency drainage when the primary drains clog or are overwhelmed. Confirm that drains and scuppers are clear and that those overflow paths actually work, since they are what save a roof in a major downpour. Then clear the roof of loose debris and trim back overhanging branches, since much of the material that becomes a projectile in high wind starts on the rooftop itself.
Finally, document the roof system's condition with dated photographs. A clear pre-storm record speeds any insurance claim and gives your contractor a reference point afterward.
Ellen Thorp is President and Managing Chair of the Coalition for Sustainable Roofing, an organization representing building products manufacturers that promote holistic roof system design and sustainable roofing assemblies. With 17 years at the intersection of roofing, building science and public policy, she builds coalitions that advance sustainability with manufacturers, designers and policymakers at every level of government. She participates in ASHRAE standards development and the ICC code development process, and holds leadership positions with the NAM-Council of Manufacturing Associations and the National Institute of Building Sciences. She holds a bachelor's degree in political science, a master's degree in education policy and the Certified Association Executive (CAE) credential.
