ICC Commercial Building Inspector Practice Test

To achieve a 4-hour fire rating for a lightweight concrete floor slab, what is the minimum thickness required?

1. 4.5 inches

2. 5.1 inches

3. 6.0 inches

4. 6.5 inches

The correct answer is: 5.1 inches

To achieve a 4-hour fire rating for a lightweight concrete floor slab, the minimum thickness required is 5.1 inches. This thickness is determined based on building codes and standards that outline the necessary fire resistance ratings for various structural components in commercial construction. Concrete is an effective material for fire resistance due to its non-combustible properties. Its ability to withstand high temperatures and retain structural integrity for extended periods is crucial in fire-rated assembly. The thickness ensures that when subjected to fire, the slab will not lose its load-bearing capacity within the specified time frame. The specified minimum thickness of 5.1 inches is essential because adequate mass and insulation provided by the slab are needed to limit the temperature rise on the exposed surface during a fire. A thicker slab beyond the minimum may offer additional safety margins, but the standard 5.1 inches meets the requirements for achieving the desired fire rating of 4 hours.