Which construction type uses heavy timber interior framing and noncombustible exterior walls?

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

Answer: (B)

Heavy timber interior framing with noncombustible exterior walls describes Type IV construction. This type uses large-dimension timber for the structural framing inside, while the exterior walls are made of noncombustible materials such as masonry or concrete. The combination provides substantial fire resistance and a distinctive fire behavior: the heavy timber inside can char in a controlled way and maintain structural integrity for longer, while the noncombustible exterior walls slow exterior flame spread.

In contrast, Type I and Type II are noncombustible throughout, Type III has noncombustible exterior walls but typically does not use heavy timber for interior framing, and Type V is wood-frame construction throughout.