A building with structural members made of wood that is partially or wholly constructed as heavy timber is classified as?

A building with structural members made of wood that is partially or wholly constructed as heavy timber is classified as Type IV Construction. This classification is significant due to the specific characteristics that heavy timber construction presents.

Type IV Construction is characterized by the use of dimensional lumber, which is typically larger in size and provides considerable resistance to fire. The heavy timber members, which must be at least 8 inches in dimension, contribute to the building's structural integrity while also allowing for enhanced fire resistance compared to lighter wood construction. This type of construction often provides the advantage of lower fire spread and better durability under fire conditions, making it suitable for certain types of buildings, such as those requiring a larger open space without many internal load-bearing walls.

In contrast, Type I (non-combustible materials), Type II (non-combustible materials with some combustible components), Type III (constructed of exterior masonry walls and interior framing of wood), and Type V (completely combustible construction made of wood) focus on different material requirements and structural characteristics, which do not align with the heavy timber classification. Thus, the unique aspects of Type IV Construction, specifically its heavy timber components, affirm its classification in the context of building construction types.