What distinguishes a Class 4 structure?

A Class 4 structure is specifically characterized by having masonry walls and roofs made of metal or other non-combustible materials. This classification is important in insurance and construction because it indicates a higher level of fire resistance compared to structures constructed with combustible materials. The use of masonry provides durability and contributes to the building's overall strength, while the non-combustible roof minimizes fire risk.

Class 4 structures are often used in commercial and industrial settings where fire safety and structural integrity are critical considerations. This makes them a preferred choice for insurance underwriting, as they present a lower risk of fire loss.

The other options do not accurately capture the defining characteristics of a Class 4 structure. For instance, a Class 4 structure is not defined simply by having masonry walls with wooden roofs, or all parts made of metal, as these would not meet the non-combustibility requirements that distinguish this class.