Which construction type is characterized by the least resistance to fire spread?

Type V construction is characterized by the least resistance to fire spread because it consists primarily of combustible materials, such as wood framing. This type includes structures where the walls, roofs, and floors are made of materials that can easily ignite and contribute to the rapid spread of fire.

In addition to the materials used, Type V construction often lacks the fire-resistive features that would impede the movement of flames and smoke. Consequently, this type of construction poses a significant risk during a fire, as the lightweight wood-frame structures can fail quickly due to combustion, leading to potentially hazardous conditions for occupants and firefighters alike.

The other construction types, while varying in their fire resistance abilities, utilize more fire-resistant materials or greater separation between combustible elements. For example, Type II and Type III include noncombustible and limited combustible materials, providing better fire resistance compared to Type V. Type IV structures are made primarily of heavy timber, which exhibits better fire resistance due to its mass. Thus, when considering the various construction types, Type V stands out due to its inherent vulnerabilities regarding fire safety.