Hail Impact Ratings: What They Mean for Commercial Roofing Durability

Hailstorms are more than a passing weather event—they can leave lasting damage, especially for commercial properties. A single storm can dent metal panels, crack membranes, and weaken roofing systems, creating the need for extensive repairs and interrupting daily operations. Without the right materials, minor impact damage can escalate into leaks, insulation failure, and structural deterioration. 

Hail impact ratings provide a clear standard for measuring a roofing material’s ability to withstand these conditions. Developed through rigorous testing, they help commercial property owners select roofing systems that offer greater durability, reduced maintenance needs, and long-term cost savings. 

Learn how hail impact ratings are determined, how different commercial roofing materials compare, and what businesses should consider when investing in a roofing system built for resilience. 

Understanding Hail Impact Ratings

Not all roofing materials are built to handle the impact of a hailstorm. While some can endure repeated strikes without significant damage, others crack, puncture, or lose their protective layers after just one storm. 

Because hailstorms vary in intensity, impact ratings provide a comparative way to gauge performance rather than an absolute guarantee of protection. A Class 4-rated roof may not be completely immune to damage in an extreme storm, but it will fare significantly better than lower-rated materials. 

For commercial buildings, where roof integrity directly affects long-term maintenance costs and structural performance, choosing the right materials is essential. 

How Hail Impact Ratings Are Tested 

Hail impact ratings aren’t based on assumptions—they are assigned through controlled testing conducted by industry organizations. 

The two most used testing standards are UL 2218 and FM 4473, both of which simulate hail impacts on different roofing materials to assess their resistance to damage. 

UL 2218 focuses on testing the impact resistance of flexible roofing materials, while FM 4473 is used to assess how rigid materials, such as wood shakes, slate, and metal roofing, withstand impact. 

UL 2218: Steel Ball Impact Test 

Under Underwriters Laboratories (UL) Standard 2218, roofing materials are tested for impact resistance using steel ball testing. In this process: 

• Steel balls of varying sizes, ranging from 1.25 inches (Class 1) to 2 inches (Class 4) in diameter, are dropped from heights of 12 to 20 feet onto roofing samples. 

• The projectiles simulate the force of hailstones striking a roof at high speeds, closely replicating real-world storm conditions. 

• After the impact, the material is examined for signs of damage, including cracks, punctures, or structural weakening. 

• Based on the results, materials are assigned a Class 1 to Class 4 rating, with Class 4 indicating the highest level of resistance to hail impact. 

The different classifications reflect the size of the projectiles used in testing: 

• Class 1 uses a 1.25-inch ball, 

• Class 2 uses a 1.50-inch ball, 

• Class 3 uses a 1.75-inch ball, 

• Class 4 uses the largest, 2-inch ball, offering the most protection. 

FM 4473: Ice Ball Impact Test 

The Factory Mutual (FM) 4473 test takes a different approach by using ice spheres instead of steel balls. The test is considered more realistic because it simulates the actual composition of hailstones. 

• Ice balls are propelled at high speeds (using compressed air) to mimic the velocity of real hail. 

• The material is assessed for surface dents, fractures, and internal damage. 

• The test measures how well a material absorbs impact energy, which can indicate its resistance to future hailstorms. 

Hail Impact Rating Classifications 

Once materials undergo testing, they are assigned a classification based on their performance. Both testing systems use a Class 1 to Class 4 scale: 

• Class 1: Minimal impact resistance. These materials are likely to suffer cracks, dents, and punctures from small hail. 

• Class 2: Moderate resistance, offering slightly better performance but still vulnerable to big hailstorms. 

• Class 3: Good impact resistance, withstanding larger hail impacts but still at risk of surface damage. 

• Class 4: Materials with the highest impact resistance that withstand the force of a 2-inch steel ball dropped from 20 feet. They are the best option for hail-prone areas. 

For commercial properties in regions where hail is common, Class 4 materials are strongly recommended due to their ability to reduce long-term repair costs and improve structural durability. 

Common Roofing Materials and Their Hail Resistance 

Asphalt Shingles 

One of the most popular roofing materials, asphalt shingles are favored for their cost-effectiveness and easy accessibility. However, they are generally more vulnerable to hail damage compared to some other roofing materials. 

The impact of larger hailstones can cause dents, cracks, and granule loss. As asphalt shingles are designed to be flexible, they can absorb some impact, but the larger and harder the hailstone, the more likely it is that damage will occur. 

The impact resistance of asphalt shingles can be enhanced by opting for higher-quality, impact-resistant versions. These shingles often use fiberglass reinforcement to increase their durability. 

Metal Roofing 

Metal roofing is considered one of the most durable options when it comes to hail resistance. Metal panels, such as steel or aluminum, can withstand the impact of hailstones without sustaining significant damage. The material's inherent rigidity and smooth surface prevent denting and puncturing. 

Yet, the performance of metal roofing can vary based on the thickness of the material and the installation method. Thicker, high-quality metal roofs typically perform better than thinner ones.  

Additionally, metal roofs can be prone to cosmetic damage, such as minor denting, but this does not usually affect their performance or integrity in the long term. 

Wood Shakes 

Wood shakes offer a natural, aesthetically pleasing roofing option for many commercial properties. However, they tend to be more vulnerable to hail damage than synthetic or metal materials. 

Hail can cause cracking, splintering, and breakage in wood shakes, especially during strong storms with larger hailstones. Wood shake roofing may require more frequent repairs or replacement after a hailstorm compared to more durable materials like metal or modified bitumen. 

The thickness and age of the wood shakes can also influence how well they handle impact. 

Clay and Concrete Tiles 

Clay and concrete tiles are among the most robust roofing materials available. They offer excellent durability against hail damage, especially larger hailstones. The dense, rigid nature of these tiles makes them highly resistant to cracking or puncturing under impact. 

The main concern with clay and concrete tiles is their fragility in terms of breakage upon a direct impact. If a heavy object or larger hailstone strikes them at a vulnerable angle, the tiles may crack or shatter. The roofing system's installation and the tile's design can influence its resilience against hail. 

Synthetic Roofing Materials 

In recent years, synthetic roofing materials have become more popular due to their enhanced durability and hail resistance. Materials like modified bitumen, TPO (Thermoplastic Olefin), and rubber roofing are known for their ability to absorb impact without significant damage. 

Synthetic materials are often reinforced with fiberglass or polymers to improve their resistance to hail and extend their lifespan. They are also lightweight, making them easier to install and maintain. 

While they are often more expensive than traditional options, the long-term resilience of synthetic materials can offer better value for commercial properties in hail-prone areas. 

Why Hail Impact Ratings Matter for Commercial Roofing 

Reduced Maintenance and Repair Costs

Materials with higher hail impact ratings experience less damage during storms, reducing the need for frequent repairs. Lower-rated materials may develop cracks and punctures, leading to leaks and interior damage. Over time, investing in a Class 4 roof can save thousands in maintenance expenses. 

Insurance Benefits 

Many insurance companies offer discounts on policies for commercial buildings that use Class 4 impact-rated roofing materials. Because these materials are less likely to sustain damage, they lower the risk of claims—a factor that insurers take into account when determining coverage rates. 

Compliance with Building Codes

In hail-prone states like Texas, Colorado, and Oklahoma, building codes may require impact-resistant roofing materials for commercial structures. Compliance ensures that buildings remain eligible for insurance coverage and meet local regulations designed to improve safety and durability. 

Long-Term Property Value

A roof with a high hail impact rating adds value to a commercial property. Prospective buyers and investors see impact-resistant roofing as a long-term asset that minimizes future costs. In contrast, properties with outdated or low-rated roofing systems may face depreciation and higher ownership costs. 

How to Choose the Right Roofing System for Hail-Prone Areas 

The selection of an optimal roofing system requires consideration of multiple factors beyond impact ratings. 

• Geographic and Climatic Considerations: Regions experiencing frequent hailstorms necessitate the prioritization of Class 4 materials. Meteorological data analysis aids in determining risk exposure levels. 

• Budgetary Constraints and Cost-Benefit Analysis: While higher-rated materials incur greater initial costs, the long-term reduction in repair expenses and insurance premiums offsets these investments. 

• Reinforcement and Coating Applications: Additional protective measures, including elastomeric coatings, impact-resistant underlayments, and reinforced membranes, enhance overall durability. 

• Professional Roof Assessments: Evaluations conducted by roofing specialists and contractors ensure that material selection aligns with structural load-bearing capacities and environmental exposure levels. 

Find the Most Suitable Commercial Roofing for Your Property with BlueTeam 

The benefits of investing in impact-resistant roofing extend beyond immediate structural protection. Reduced maintenance costs, enhanced weather resistance, and compliance with industry standards contribute to long-term financial savings. 

For commercial properties requiring expert assessment, roofing installation, and restoration services, BlueTeam offers comprehensive solutions designed to maximize resilience against hail-related damage.  

Contact BlueTeam today for a professional consultation and ensure that your commercial property remains protected under all weather conditions.