Which construction type is heavy timber and is least likely to collapse, with the weight-bearing capacity of the large wood members resisting collapse unless they've been affected by a large volume of fire?

Which construction type is heavy timber and is least likely to collapse, with the weight-bearing capacity of the large wood members resisting collapse unless they've been affected by a large volume of fire?

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

Answer: (D)

Heavy timber construction uses very large wood members whose mass helps them resist heat and sustain load during a fire. As wood chars on the surface, it forms an insulating layer that slows heat penetration, so the inner portion keeps its strength longer. The structure can carry its weight through a fire for a longer period until a large volume of fire burns enough material to reduce the cross-section significantly. That’s why this construction type is the least likely to collapse early. Other systems rely on noncombustible materials or smaller wood members that don’t provide the same built-in resistance, so they can lose strength more quickly under fire conditions.

Heavy timber construction uses very large wood members whose mass helps them resist heat and sustain load during a fire. As wood chars on the surface, it forms an insulating layer that slows heat penetration, so the inner portion keeps its strength longer. The structure can carry its weight through a fire for a longer period until a large volume of fire burns enough material to reduce the cross-section significantly. That’s why this construction type is the least likely to collapse early. Other systems rely on noncombustible materials or smaller wood members that don’t provide the same built-in resistance, so they can lose strength more quickly under fire conditions.