The provisions of this Code are not intended to prevent the installation of any material or to prohibit any method of construction not specifically prescribed by this Code, provided that any such alternative has been approved. An alternative material or method of construction shall be approved where the Code 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 offered is, for the purpose intended, at least the equivalent of that prescribed in this Code in quality, strength, effectiveness, fire resistance, durability and safety. (105.2)