Which type of construction features heavy timber and has no voids?

Type 4 construction is characterized by the use of heavy timber, also known as mill construction, and is specifically designed to avoid void spaces within its framework. This type of construction is notable because it utilizes large-dimensional lumber that provides significant strength and fire resistance. The absence of voids helps to limit the risk of fire spread within the structural elements, as fire cannot easily travel through concealed spaces as it might in other construction types.

In contrast, the other construction types each have distinct characteristics that do not align with the heavy timber and void-free features of Type 4. For example, Type 1 construction, which consists of fire-resistive materials, typically includes concrete and steel with a focus on fire resistance but does not incorporate heavy timber. Type 5 construction, often involving lightweight wooden framing, is the least fire-resistant and can have numerous voids. Lastly, Type 3 construction, also known as ordinary construction, combines both fire-resistive and wood elements but does involve voids that can contribute to fire spread. Thus, Type 4 construction stands out for its use of heavy timber and the absence of voids, making it a crucial consideration in fire safety planning and risk assessment.