What is the key factor that differentiates Class 5 construction from Class 4?

The key factor that differentiates Class 5 construction from Class 4 is the construction rated above a 2-hour fire resistance. Class 4 construction typically involves materials that provide a 2-hour fire rating, meaning that the elements of the building can withstand fire for that duration without failing. In contrast, Class 5 construction involves structures that are designed with even greater fire resistance, exceeding this 2-hour threshold. Such classifications are important as they inform structural integrity in the event of a fire, dictating the types of materials used and the overall safety protocols associated with different building types.

Option A, which refers to the use of combustible materials, is not exclusive to Class 5, as Class 4 can also incorporate some combustible elements depending on the overall fire rating context. Option B speaks specifically to the fire rating already established in Class 4, indicating it lacks the additional fire resistance characteristic of Class 5. Meanwhile, option D points to noncombustible structures, which applies to certain Class 4 and Class 5 constructions, but it does not directly address the crucial factor of fire resistance rating that distinguishes these two classes. Thus, the focus on fire resistance level is what makes option C the distinguishing feature between Class 4 and Class