SEDL / STP / STP1349-EB / STP13300S

The Deteriorating Artificial Slate

Gumpertz, WH
Senior Principal and Senior Staff Engineer, Simpson Gumpertz & Heger Inc., Consulting Engineers, Arlington, Massachusetts

Condren, SJ
Senior Principal and Senior Staff Engineer, Simpson Gumpertz & Heger Inc., Consulting Engineers, Arlington, Massachusetts

Pages: 19    Published: Jan 1999

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Abstract

Wood fibers were substituted for asbestos fibers as reinforcing in cement-fiber shingle products used as imitation roofing slate when governmental action outlawed the use of asbestos in this application. Our field experience with many installations of one brand of these new products, however, has been unsatisfactory. We have observed the rapid deterioration, often within two to three years, of shingles in service, primarily by the development of extensive cracking. Our research finds that these failures result from layering of the mortar materials during manufacture, combined with petrifaction and loss of ductility of the organic fibers. We suggest changes to the requirements of the applicable ASTM standard to help ensure that the product has the attributes necessary for satisfactory performance in service.