Asphalt shingle performance boils down to a few common factors: impact-resistant strength provided by asphalt coatings saturated on a fiberglass mat and high wind resistance. The next is a high-performance “sticky” modified asphalt sealant that adheres shingles to a roof and maintains that tack under high winds and cold temperatures. If the coating and sealant don’t fail, the shingles will maintain a strong waterproof barrier between your home and the harsh elements outside.
Sealant uplift strength is relatively easy to test. Florida International University boasts a “Wall of Wind” that can simulate hurricane wind speeds, and mechanical tests can give an accurate prediction of how sealant performance will translate to the field. Impact is not so straightforward. There is a hot debate among third parties on how impact should be measured, and which methodology accurately represents real-world applications. It would prove tough to measure the performance of shingles in the real world by any consistent measure. The factors that can cause shingles to break could be as random as a falling tree branch or as devastating as softball-sized hail. If performance is going to be measured, there must be a standard to measure performance against. The two popular tests today are known as the steel ball test (UL 2218) and the ice ball test (FM 4473).
Underwriters Laboratories is a third-party global safety certification company that evaluates all shingles, ranking them from Class 1 to Class 4, with higher classes indicating stronger impact performance.
The chart below summarizes the steel ball size and drop heights required to pass:
| CLASS DESIGNATIONS FOR UL 2218 | ||||
| CLASS 4 | CLASS 3 | CLASS 2 | CLASS 1 | |
| Ball Size | 2-inch diameter | 1 3/4-inch diameter | 1 1/2-inch diameter | 1 1/4-inch diameter |
| Drop Height | 20 feet | 17 feet | 15 feet | 12 feet |
For a shingle to reach a Class 4 rating, it must handle a drop from the associated height and then have a light shining behind it with no visible light coming through the impact site.
The next test method involves shooting similarly sized ice balls (FM 4473) at high speeds at the shingles. This method is popularized by the Insurance Institute for Business and Home Safety (IBHS). Every two years, the group gathers every Class 4 shingle on the market and evaluates each one in three categories: dents and ridges, tears and granule loss.
In 2025, IBHS noted an emergence of Class 3 shingles on the market and incorporated them into its testing protocol. Following the typical train of logic, Class 3 shingles would not rate as high as Class 4 shingles. This round of the IBHS evaluation cycle produced results that raise questions about the testing methodologies.
To be clear, data is data, and IBHS is simply reporting its results according to its evaluation methods. That said, the first confusing result from this methodology shows Class 3 shingles performing better than Class 4 shingles. Without calling out specific brands, an independent observer can figure out which shingle coatings are modified or unmodified, and which ones boast an impact warranty, and which don’t. Given this kind of discrepancy in results, I think the validity of the ice ball method (FM 4473) needs to become the subject of independent testing to settle which method is effective in evaluating impact performance.
On the surface, steel balls would not seem like a real-world indicator to match ice ball performance, but they are a standard that can identify the difference in performance between polymer-modified and unmodified shingles. I think a shotgun result like the IBHS impact study needs to bring evaluation of shingle ratings under scrutiny and bring the evaluation of current and new methodologies to the forefront of independent research.
Nichols is Vice President of Sales at Polyco. He participated in the Asphalt Institute EPIC Leadership Program.
