Until recently, sarking material consisted of a paper core with various coatings. The sarking is classified on tensile strength since this is an easier property to measure than tear strength. Although sarking fails in practice by tearing around the fixings, which is tearing rather than tension, the tension test is still suitable because there is a relationship between tear and tensile strength in any one material. The problem arose in the change of the core material from paper to a plastic. This resulted in a different relationship between the tensile and tear properties.
Some plastics have a lower tensile strength than a paper of the same tear strength.
Thus, classification by tensile strength is not treating these materials fairly. In the meantime the Technical Assessment has enabled the introduction of the product into the marketplace. Clearly there is a need to keep performance-based codes and standards continually revised and reassessed in the light of developments in technology. For a second example, consider floor coverings. The BCA, for certain public buildings, has a requirement that floor coverings will have a fire performance that will not inhibit safe evacuation of the building in the event of a fire.