Designing Storm-Rated Metal Buildings for Georgia’s Tornado Zones
Article Summary
Georgia experiences frequent tornado activity, making storm-resistant construction increasingly important for commercial buildings. Pre-engineered metal buildings (PEMBs) can be designed to withstand high winds and tornado conditions when they meet standards like ICC 500 and FEMA 361. However, even high-quality materials can fail if roof systems, fasteners, bracing, and anchoring are improperly installed. This article explains how storm-rated metal buildings improve resilience, where Georgia tornado risks are highest, and why erection quality and connection details matter more than many owners realize.
How PEMBs Improve Tornado Resilience Through Better Engineering, Anchoring, and Design
Every region is at some risk for natural disasters, and while the Southeastern U.S. is not prone to earthquakes or tsunamis it does experience severe storms and even tornadoes. That makes it imperative that structures in the Southeast—Georgia in particular—are built to withstand high winds.
Do Tornadoes really occur in Georgia?
Yes. Since 1950, 2,340 tornadoes have touched down in Georgia, causing more than $3 billion in property damage.
While no state beats Texas, with its average of 124 twisters per year, Georgia has an average of 40 tornadoes per year.
In 2025 alone, there were 54 tornadoes in the Peach State. But some years have been even worse. Here are some of the years with the most tornadoes in Georgia history:
2023
72
2020
77
2017
147
2011
67
2009
68
2008
86
Which Georgia counties are most prone to tornadoes?
Every county in Georgia has experienced at least one tornado.
While the entire state is vulnerable, the counties of Cherokee, Fulton, and Coweta seem to be the most tornado prone. Each has experienced more than 30 twisters since 1950.
Can a tornado damage a metal building?
Yes. Wood-framed houses and trailers are obviously more vulnerable to wind damage, but strong winds can still wreak havoc on commercial buildings made of steel or concrete. For example, long-span roof systems on large metal buildings frequently fail in high winds if not properly braced.
How much damage do tornadoes cause to commercial buildings in Georgia?
Firm statistics on tornado damage to commercial structures are not readily available. But the amount is certainly in the billions of dollars. While fatalities and the destruction of homes get more notice, tornado damage to non-residential structures can be catastrophic:
➲ On November 7, 1995, an F2 tornado in Dougherty County caused the partial collapse of a supermarket, resulting in numerous injuries and $10 million in damage
➲ In one of the worst weather-related events in Georgia history, an EF3 tornado touched down on January 22, 2017, traveling 70 miles through Dougherty, Worth, Turner, and Wilcox Counties. Besides destroying numerous homes and resulting in five fatalities, it caused the partial collapse of a warehouse, shifted the roof of one concrete building, and destroyed two church buildings made of concrete block. Total damage was estimated at a staggering $300 million
What is a storm-rated metal building?
Structures that are considered storm-rated must be able to withstand high-velocity winds and offer protection from flying debris. Local building codes typically have specific requirements for such buildings in addition to those set by state, federal, and transnational agencies. Buildings that meet the highest standards can qualify as storm shelters or safe rooms, where people can seek safety in the event of a tornado or hurricane.
Here are three levels of regulations a storm-rated building in Georgia must comply with:
- ICC 500 is a set of requirements for storm shelters formulated by the International Code Council (ICC) and the National Storm Shelter Association (NSSA). Its provisions have been adopted by the International Building Code (IBC), whose standards are mandatory for new construction in many jurisdictions. To receive ICC 500 certification, a structure must be able to withstand winds of 250 mph and pass missile impact tests that simulate flying debris. The integrity of the entire structure must also be demonstrated, with specific requirements for components such as doors, windows, roof systems, and foundations. Tests for ICC 500 certification are administered by third-party providers.
- FEMA 361 is a guide for constructing community shelters and safe rooms promulgated by the Federal Emergency Management Agency (FEMA). It provides specific criteria for the “design, construction, installation, and inspections of safe rooms” and other related topics.
- Georgia’s state construction codes incorporate ICC 500 specifications for storm shelters and similar structures. Standard commercial structures must comply with IBC Figure 1609.3(1). Critical/high occupancy buildings must comply with IBC Figure 1609.3(1) or wind resistance of 135 mph, whichever is greater.
How can poor installation compromise a storm-rated metal building?
Even when the correct materials are used, a metal building can be exposed to risk if the components aren’t properly installed. Here are some areas where poor installation can lead to problems:
❌ Improperly installed roof panels. If roof panels are misaligned or clips are installed incorrectly, the roof’s wind resistance can be compromised.
❌ Improper torquing on roof fasteners. The fasteners that join the roof panels to the frame are important in a metal building. If they are under-tightened, they can loosen over time, creating gaps and exposing the panels to uplift. If they are over-tightened, the washers can be damaged, exposing the roof to leaks.
❌ Inadequate bracing. Hurricane straps and other braces are important in protecting a building from the impact of lateral forces. If they are omitted or underutilized, the building is vulnerable to strong winds.
❌ Improper anchoring. A steel building’s frame is secured to its foundation with anchor bolts. If those bolts are not the correct size or are misaligned, the entire structure can be wrenched from its foundation.
What are the most common failure points in metal buildings during high-wind events?
The roof is the most vulnerable part of a metal building when high winds occur. Wind may force the outside edge of a roof panel up, exposing the entire roof to uplift. Misaligned panels and seams can also be lifted during a wind event, and panels with poorly attached fasteners may become separated.
Doors and windows are also vulnerable points. High winds can damage seals and tracks, causing interior as well as exterior damage.
Why do connection details matter more than materials in storm-rated metal buildings?
The fasteners, braces, and anchor bolts that hold a structure together are the source of its strength. These components transfer stress loads through the structure to the foundation. Their quality and proper installation are thus key to the building’s ability to withstand wind events.
How does steel erection quality impact a building’s storm resistance?
Top-quality steel erection follows design specifications precisely without cutting corners. Care is taken to attach the roof panels, frame elements, braces, and other components correctly—not just quickly. Fasteners are torqued down just right, and anchor bolts are aligned precisely. This ensures that wind and other stress loads are transferred efficiently to the foundation, minimizing the risk of damage.
When the job is done right, the benefits are many: work doesn’t need to be redone, the job can proceed on schedule, and liability risk from poor workmanship is avoided.
The result is a building that can stand strong, and provide decades of service.
FAQ Section
What wind speeds can storm-rated metal buildings withstand?
Storm-rated metal buildings may be engineered to withstand winds exceeding 135 mph, while ICC 500-certified storm shelters can withstand winds up to 250 mph.
Are metal buildings safer than wood buildings during tornadoes?
Metal buildings generally perform better than wood-framed structures during high-wind events, especially when properly engineered and anchored.
What is ICC 500 certification?
ICC 500 is a building standard for storm shelters developed by the International Code Council and the National Storm Shelter Association. It includes wind resistance and missile impact testing requirements.
What are the most common weak points in a metal building during a tornado?
Roof systems, fasteners, seams, doors, windows, and anchor connections are among the most common structural failure points during severe wind events.
Why does installation quality matter in PEMB construction?
Even high-quality materials can fail if braces, fasteners, roof panels, or anchor bolts are installed incorrectly. Proper steel erection ensures stress loads transfer safely to the foundation.
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