Building codes by their nature tend to be limiting—they limit designs, materials and construction methods to those specifically prescribed in codes and meeting codes' performance requirements. However, most codes contain provisions that allow building officials to approve alternatives that are not specifically permitted by the codes.
You should be aware of these alternative approval provisions because they apply to an increasing number of roofing products and roof systems.
The 2006 edition of the International Building Code (IBC) includes the following statement regarding alternatives: "104.11 Alternative materials, design and methods of construction and equipment. The provisions of the code are not intended to prevent the installation of any material or to prohibit any design or method of construction not specifically prescribed by this code, provided that any such alternative has been approved. An alternative material, design or method of construction shall be approved where the building official finds that the proposed design is satisfactory and complies with the intent of the provisions of this code, and that the material, method or work is, for the purpose intended, at least the equivalent of that prescribed in this code for quality, strength, effectiveness, fire resistance, durability and safety."