Which construction type uses heavy timber members for structure and allows larger interior open spaces?

• A. Type I (Fire-Resistive)
• B. Type II (Noncombustible)
• C. Type IV (Heavy Timber)
• D. Type III (Ordinary)

Answer: (C)

Heavy timber construction uses large-dimension timber members for the structural frame, which can span longer distances and carry loads with fewer columns. That capability creates the option for larger, unobstructed interior spaces like wide halls or open atriums. At the same time, these big wooden members have inherent fire-resistance: as they burn, they form a protective char layer that slows heat penetration, helping the structure maintain integrity long enough under fire exposure. Because of these combined properties—strong, long-span timber and predictable fire behavior—this construction type is chosen to achieve large open interiors while meeting fire safety requirements. Other types rely on noncombustible materials or lighter framing, which typically requires more columns and partitions, limiting how large an open interior can be.