Which construction type is commonly referred to as heavy timber construction?

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

Answer: (C)

Heavy timber construction is identified by using large solid wood members—the structural frame is built from substantial timbers rather than light framing or noncombustible systems. This approach is categorized as Type IV in building codes. The mass of the timbers allows them to char slowly in a fire, creating a protective layer that preserves structural integrity for longer than lighter wood or many other framing methods, which is why it’s recognized for its higher inherent fire resistance. Exterior walls are typically noncombustible, and interiors often showcase the exposed timber—giving the style its distinct, sturdy character.

Compared to other construction types, which rely on noncombustible materials like steel and concrete (providing the highest fire resistance) or mix noncombustible exterior walls with combustible interior framing, heavy timber stands out for its timber frame that remains intact longer under fire. This combination of large timber members and mass is the distinguishing feature. In practice, this construction is commonly referred to as Type IV.