Which construction type is least likely to require fire resistance ratings?

Type II construction, also known as non-combustible construction, is least likely to require fire resistance ratings because the materials used are typically fire-resistive and designed to prevent the spread of fire. In this type of construction, the structural elements are made of non-combustible materials such as steel or concrete, which inherently do not contribute to the fire load or fuel contribution. Consequently, the need for additional fire resistance ratings is minimized compared to other types of construction that may incorporate combustible materials that require additional fire protection measures.

In contrast, Types I, III, and IV constructions often include structural elements or finishes that are combustible or have lower fire-resistance characteristics, leading to the necessity for fire resistance ratings to enhance safety and slow the progression of fire. Type I construction is typically built with fire-resistive materials for high-rise buildings, Type III construction involves a mix of combustible and non-combustible elements, and Type IV construction (heavy timber) embraces larger wooden elements that, while offering some natural fire resistance, still require ratings to address potential fire hazards.

Thus, Type II construction's inherent properties afford it a reduced need for fire resistance ratings, aligning with the principles of fire protection in building design.