The code revisions seemed to suggest conventional felt underlayment could only be used in limited situations, and even then would have to be doubled. In other applications, a D226 Type II roofing felt would be required, but it cost $6 more a roll, and was harder to lay down flat. Warrior Roofing Manufacturing's newly developed Elephant Skin, a synthetic felt, can replace old school felt, but it's 20 times tougher, won't tear or puncture during installation and can be left exposed to sunlight for up to 90 days, according to the manufacturer. The product was designed to reduce slippage when wet, and unlike heavy D226 felt won't show wrinkles in a finished shingled roof. It covers 1,000 square feet per roll, about five times as much as standard D226 felt, and a roll weighs about 24 pounds compared to the 57 pounds for a 200-square-foot roll of felt. It costs more per roll but in the end is about 40 percent cheaper.

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