Which is the type IV classification of building construction?

• A. Heavy timber
• B. Wood frame
• C. Non-combustible construction
• D. Ordinary construction

Answer: (A)

Type IV construction is heavy timber. This design uses large-dimension wood members—big beams and columns—forming the structural frame. The mass of solid timber char rate creates a protective layer that slows burning and helps the structure maintain integrity longer during a fire. Because of this, the fire performance relies on the size and solid nature of the timber rather than on noncombustible metal or concrete for the primary frame. In contrast, wood frame or lightweight wooden construction relies on smaller, more combustible members, noncombustible construction uses steel or concrete for the skeleton, and ordinary construction typically mixes noncombustible exterior walls with combustible interior elements. So, the Type IV classification specifically corresponds to heavy timber.