In Type IV construction, minimum fire resistance rating for loadbearing walls is?

In Type IV construction, minimum fire resistance rating for loadbearing walls is?

• A. One hour
• B. Two hours
• C. Three hours
• D. Four hours

Answer: (B)

In Type IV construction, the heavy timber frame itself provides substantial fire resistance, so the code sets a two-hour minimum for loadbearing walls. That rating means the wall can keep its structural capacity and limit heat transfer for about two hours under standard fire exposure, giving occupants more time to escape and firefighters a safer window to work. The char that forms on timber during a fire acts as an insulating layer, helping protect the core structure longer than a lighter construction would. One hour would not give enough time for protection of the heavy timber frame, while three or four hours would exceed what's required for typical Type IV buildings. Therefore, the minimum rating is two hours.

In Type IV construction, the heavy timber frame itself provides substantial fire resistance, so the code sets a two-hour minimum for loadbearing walls. That rating means the wall can keep its structural capacity and limit heat transfer for about two hours under standard fire exposure, giving occupants more time to escape and firefighters a safer window to work. The char that forms on timber during a fire acts as an insulating layer, helping protect the core structure longer than a lighter construction would. One hour would not give enough time for protection of the heavy timber frame, while three or four hours would exceed what's required for typical Type IV buildings. Therefore, the minimum rating is two hours.