Slate association takes issue with installation article

As executive director of the National Slate Association, I was deeply concerned about "The installation checklist," May issue, by Dave DeRogatis, director of composites for Ply Gem Industries Inc., Cary, N.C.

ASTM International is responsible for providing critical testing for many industries, including roofing. Roofing specifications are based on ASTM International testing of materials and, to give the testing meaning, the materials are specifically defined. Most testing concerns structural integrity and material durability with the goal of public information and safety.

ASTM C119, "Standard Terminology Related to Dimension Stone," defines slate as "a metaphorical rock … composed mostly of micas, chlorite and quartz … distinguished by slaty cleavage … which allows the latter to be split into sheets."