The “UL 2218 Impact Resistance of Prepared Roofing Materials” standard, developed by Underwriters Laboratories (UL), describes a test method that provides impact resistance data for evaluating steep-pitched roofing materials. Under this standard, prepared roofing materials are considered to be small units, sheets, or panels designed to be installed in multiple layers in overlapping rows on roofs with a pitch of 2:12 (16,67 percent) and higher.
Impact resistance tests for the evaluation of low-slope roof systems are covered under the "UL 2218A Impact resistance of roof systems" standard.
This testing method evaluates the impact of a steel ball at selected locations where the test setup is most vulnerable (e.g., edges, corners, unsupported sections, and joints).
This testing method does not evaluate the effects of weathering, temperature, aging, or similar factors on the impact resistance of prepared roofing materials. These and other factors, including time, roof slope, roof system configuration, and application, affect the field performance of prepared roofing materials. The aim of this test is not to address all of these factors.
The impact energies used in this standard are derived from the impact energies of actual hailstones (Appendix A). However, largely due to the effects mentioned above, there is currently no established direct correlation between the performance of prepared roofing materials when exposed to hailstones and steel balls. Consequently, this test method does not provide a direct basis for comparing expected performance under all hail conditions, but it does provide a basis for comparing the response of prepared roofing materials when exposed to the impact energies described herein.
UL 2218 is a widely recognized testing standard. This standard provides a standardized laboratory method for evaluating how well steep-pitched roofing materials (primarily asphalt tiles, but also applicable to other prepared materials) resist impacts such as hail.
This standard simulates a hailstorm by dropping steel balls of increasing size from specific heights, thereby creating an effect equivalent to the kinetic energy of natural hailstones of corresponding diameters. It has become a significant benchmark in the roofing industry, particularly in regions prone to hail, where products achieving higher ratings can benefit from insurance premium reductions.
The UL 2218 standard focuses on steep-pitched roofing materials (typically those installed on roofs with a slope greater than 2:12). This standard evaluates resistance to punctures or tears that could lead to water ingress. A related standard, UL 2218A, covers low-pitched roofing systems.
This test method does not evaluate the following:
This testing method uses steel balls dropped from calculated heights onto test specimens. The impacts occur at sensitive points (e.g., edges, corners, unsupported areas). After each drop (typically two impacts per location), the specimens are checked for tears, cracks, fractures, or openings visible from the back. This check is usually performed by bending flexible materials over a mandrel. Any such damage is counted as a failure for that grade level.
The UL 2218 standard defines four classes, where higher numbers indicate greater resistance:
Products that reach Class 4 are marketed as impact-resistant or hail-resistant and must withstand two impacts at the same point without damage.
The UL 2218 standard is considered important for the following reasons:
While valuable, the UL 2218 standard is a laboratory test performed on new materials and does not fully reflect real-world conditions such as those listed below:
In conclusion, the UL 2218 standard is important because it promotes safer, more resilient homes in hail-prone areas, reduces long-term costs through insurance savings and reduced repairs, and provides a reliable tool for everyone from homeowners to insurers to assess and claim better roof performance.
This standard plays a crucial role in promoting durable roofing in areas susceptible to hail damage, helping homeowners strike a balance between cost, protection, and potential insurance savings.
For many years, our organization, with its competent and experienced team, has been understanding the needs of its clients, providing the advanced testing services they require, and assisting them in the establishment, implementation, and improvement of management systems. Within this framework, we also provide testing services compliant with the UL 2218 standard.
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