Roof coverings shall demonstrate physical integrity over the working life of the roof based upon 2,000 hours of exposure to accelerated weathering tests conducted in accordance with ASTM E838, 623, 626 or 653 listed in Chapter 35. Those roof coverings that are subject to cyclical flexural response due to wind loads shall not demonstrate any significant loss of tensile strength for unreinforced membranes or breaking strength for reinforced membranes when tested as herein required.
Interpretation of the Code:
The code mandates physical property testing of roof materials to be conducted prior to market inception. The roof materials must exhibit long-term waterproofing properties after testing, which duplicates exposure to the elements.The prerequisite testing should be completed in accordance with ASTM E838, “Practice for Performing Accelerated Outdoor Weathering Using Concentrated Natural Sunlight.” In this test method, the roof materials are set in an approved chamber that simulates natural sunlight exposure to the material for a period of 2,000 hours. At the completion of the testing cycle the material is analyzed for deterioration created through the exposure. If the material meets the test requirements it is acceptable for use in commercial and/or residential applications.
The code also states that the material must be tested for wind uplift resistance.Wind uplift tests are conducted in accordance with UL 580 or FM 4490. Low-slope materials are applied over a 12-foot by 24-foot test frame that includes roof deck construction. Once the roof materials and system have been applied over the deck an air chamber is applied over the frame and continual air pressure is exerted throughout the chamber. The material/ system must withstand wind uplift pressures that are gradually increased in one-minute increments. The last air pressure rate that progresses the full minute prior to failure is the design pressure for the system.
Steep slope roof systems are tested in wind tunnels with a 6-foot by 10-foot constructed roof installation — including the deck. Lateral wind force projected by a jet engine is applied over the system up to 140 mph. Failure of the material is exhibited through displacement (uplift) or deterioration of the material.
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