In which class of construction is everything made of and supported by noncombustible materials?

The correct choice identifies a class of construction where all components, including walls, roofs, and floors, are constructed entirely from noncombustible materials. This classification is crucial in the context of fire safety and building regulations. Noncombustible materials do not ignite or sustain combustion, which significantly enhances the fire resistance and overall safety profile of a structure.

In building codes, Class 3, or Noncombustible construction, is defined specifically to meet this criterion. The use of noncombustible materials such as steel, concrete, or masonry reduces the risk of fire spread and provides a safer environment for occupants.

The other classes mentioned have characteristics that include combustible materials. In Frame construction, for instance, wooden structures are prevalent, and thus carry a higher fire risk. Joist and Masonry construction often includes a mix of materials, allowing for some combustion-prone components. High-Rise construction does not inherently dictate that only noncombustible materials are used, although it typically requires materials that can withstand higher loads and fire exposure; it does not specifically restrict the use of combustible materials as strictly as Class 3 does. Therefore, Class 3 stands out as the only category where the entire structure is made and supported exclusively by noncombustible