When it comes to hail-resistant roofing, many people focus on the material of the roof. Will asphalt be more easily damaged than metal? Will clay tiles crack and require more frequent repair or replacement?
But there's more to impact resistance than choice of material. Looking at the laboratory testing results of prospective roofing materials is a better way to tell how well they can hold up to hail damage. If you're looking for roofing that can resist hail, there are two impact tests that you should know about.
Who Are Underwriters Laboratories?
One of the most commonly used classifications for roof material impact resistance comes from the testing of two companies: Underwriters Laboratories and FM Approvals. They are both safety certification companies that do testing and consultation, and they are on OSHA's list of Nationally Recognized Testing Laboratories. They don't only test roofing material; in fact, between the two companies, they conduct safety testing of a huge number of different products.
How Does Underwriters Laboratories Conduct Their Impact Tests?
To simulate the effect of hailstones and see how much damage a particular roofing material sustains, Underwriters Laboratories conducts impact tests with steel balls. These balls are dropped from heights designed to calibrate the force of their impact with what you would expect from a hailstorm. The laboratory makes sure to hit not only central areas but also areas such as corners and edges that might be more prone to damage.
During the test, progressively larger steel balls are used. The larger the steel balls that a roofing material can withstand without cracking, the higher its impact resistance is. This test is used mostly on flexible roofing materials like asphalt shingles or metal, but it is sometimes used on rigid materials as well. It is referred to as the UL 2218 standard.
How Does FM Approvals Conduct Their Impact Tests?
The difference between UL 2218 and FM Approvals' test – known as the FM 4473 standard – is primarily in the materials used. Instead of steel balls, FM 4473 uses balls of ice that are shot at the roofing material. And this test is designed specifically for rigid roofing materials like slate and tile.
What Results Should You Look For?
Roofing materials that have been tested for impact resistance are given a rating, and conveniently, the ratings for these two tests are similar. A class 1 rating is the lowest, meaning the roofing material cracked or showed damage with less force; a class 4 rating means that the roofing didn't crack during the test. If you're looking for a good roofing material in an area prone to hail, you'll want to look for a class 4 rating in either UL 2218 or FM 4473 impact testing.
For professional roofing, contact a company such as Freedom Roofing.