Type IV construction is described as having interior structural members that are solid or laminated wood of large dimension without concealed spaces. Which option corresponds to Type IV in this context?

• A. Type II
• B. Type I
• C. Type IV
• D. Type III

Answer: (C)

Type IV construction is heavy timber, using interior structural members made of solid or laminated wood in large dimensions with no concealed spaces. This explicit feature—large-dimension wood and the absence of hidden cavities—defines heavy timber, setting it apart from the other construction types. The other types rely on noncombustible materials (like steel or concrete) for structural elements, or on wood framing in a way that typically includes concealed spaces or lighter members (as seen in Type V wood frame or Type III with exterior noncombustible walls). Therefore, the description given aligns with Type IV.