JLC ??OCTOBER 1991 Both anecdotal evidence and a study of nearly 100 California roofs suggest that some asphaltshingle roofs with 20-year warranties are failing before the warranties terminate. Roy Bolt, a roofing contractor with McDonald and Wetle Inc., a Portland, Oregon, roofing contractor, and chairman of the residential technical and research committee of the Western States Roofing Contractors Association, has talked to numerous western contractors who have applied 20-year shingles and then had problems early in the warranty period. "Some of these things are going as soon as four years after installation," says Bolt. This anecdotal evidence is supported by a study done by Richard Tippett of Applied Roofing Technology, a roofing consulting firm. Tippett analyzed nearly 100 central California roofs and found significant degradation of 20-year shingles, including granule
