Which construction type corresponds to Heavy timber or mill construction?

Which construction type corresponds to Heavy timber or mill construction?

• A. Type 4 Construction
• B. Type 5 Construction
• C. Type 2 Construction
• D. Type 3 Construction

Answer: (A)

Heavy timber, or mill construction, is Type IV. The defining feature is a structure built with large wooden members—heavy timber columns and beams—whose size allows the wood to form a protective charring layer in a fire, helping maintain stability for a period of time. Exterior walls are noncombustible, typically masonry, while the interior relies on these substantial timber members rather than steel or light wood framing. This combination gives heavy timber its distinct fire-resistance profile compared to other types. Wood-frame construction, by contrast, uses lighter wood members and is classified as Type V. Type III has noncombustible exterior walls but uses wood interior framing, not heavy timber. Type II and Type I are noncombustible or fire-resistive systems with metal or concrete framing.

Heavy timber, or mill construction, is Type IV. The defining feature is a structure built with large wooden members—heavy timber columns and beams—whose size allows the wood to form a protective charring layer in a fire, helping maintain stability for a period of time. Exterior walls are noncombustible, typically masonry, while the interior relies on these substantial timber members rather than steel or light wood framing. This combination gives heavy timber its distinct fire-resistance profile compared to other types.

Wood-frame construction, by contrast, uses lighter wood members and is classified as Type V. Type III has noncombustible exterior walls but uses wood interior framing, not heavy timber. Type II and Type I are noncombustible or fire-resistive systems with metal or concrete framing.