What is a unique feature of Type 4 construction?

Type 4 construction, also known as "heavy timber construction," is characterized primarily by the use of heavy timber components. This type of construction incorporates solid wood beams, columns, and decking with large dimensions, which contribute to its strength and durability. Importantly, the absence of voids within the structural elements, such as concealed spaces or cavities, enhances the fire resistance of the building. This characteristic reduces the likelihood of fire traveling within the structure and provides additional safety for both occupants and responders during firefighting operations.

The other options do not accurately reflect the defining aspects of Type 4 construction. While non-combustible materials and lightweight materials may apply to other construction types, Type 4 specifically emphasizes heavy timber. Additionally, while it can be used for various building types, it is not restricted to commercial structures, further distinguishing it from the provided choices.