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Abstract
In the early 1980s, manufacturers started to respond to the market desire for a Class A fire-rated steep-sloped roofing material. Other manufacturers sought slate-like roofs that were lower in cost than natural slate. Both groups tried a variety of materials and cellulose fibers including fibers recovered from newprint, bundles of wood, and more fibrous or shrredded wood to reinforce portland cement matrixes. Previously, asbestos fiber was used with cement to form very durable asbestos-cement shingles, sidings, and sheets. Many manufacturers felt they could replace asbestos with other materials and did so offering performance warranties of 25-50 years duration. The authoris have investigated and tested eleven of these artificial shakes and slates manufactured by nine manufacturers. Hundreeds of roofs have been examined in more than 20 states. Some products failed before the installation was completed. Few survived past their tenth year of exposure. None of the artificial shakes and slates investigated are currently manufactured in the U.S. Data is provided that were generated by lab tests on thousands of specimens made by nine manufacturersm identify the reinforcements present, list some of the critical properties such as flexural strength, deflection at break, and water absorption, and the specific failure modes for each product. The principal recommendation to avoid failures of this kind is to use products that have a substantial history of effective performance in the environment to which they wil be used.
In the early 1980s, manufacturers started to respond to the market desire for a Class A fire-rated steep-sloped roofing material. Other manufacturers sought slate-like roofs that were lower in cost than natural slate. Both groups tried a variety of materials and cellulose fibers including fibers recovered from newprint, bundles of wood, and more fibrous or shrredded wood to reinforce portland cement matrixes. Previously, asbestos fiber was used with cement to form very durable asbestos-cement shingles, sidings, and sheets. Many manufacturers felt they could replace asbestos with other materials and did so offering performance warranties of 25-50 years duration. The authoris have investigated and tested eleven of these artificial shakes and slates manufactured by nine manufacturers. Hundreeds of roofs have been examined in more than 20 states. Some products failed before the installation was completed. Few survived past their tenth year of exposure. None of the artificial shakes and slates investigated are currently manufactured in the U.S. Data is provided that were generated by lab tests on thousands of specimens made by nine manufacturersm identify the reinforcements present, list some of the critical properties such as flexural strength, deflection at break, and water absorption, and the specific failure modes for each product. The principal recommendation to avoid failures of this kind is to use products that have a substantial history of effective performance in the environment to which they wil be used.
Date
11/2007
11/2007
Author(s)
Carl Cash; Stephen Condren; Werner Gumpertz
Carl Cash; Stephen Condren; Werner Gumpertz
Page(s)
16-21
16-21
Keyword(s)
shakes; slates; performance; durability
shakes; slates; performance; durability