Which two elements define a building's construction type?

• A. Structure size and occupancy type
• B. Ventilation sources and interior furnishings
• C. Presence of automatic fire suppression and alarm systems
• D. Construction materials and their performance when exposed to fire

Answer: (D)

Construction type is defined by what the building is made from and how those materials behave when exposed to fire. The two elements that matter are the actual structural materials (for example, wood, steel, concrete, masonry) and their performance under fire conditions, which is captured by fire-resistance ratings and the way the material maintains or loses strength as heat increases. This combination determines how long the structure can resist fire, how it may deform or collapse, and how compartments hold up during a fire, all of which influence firefighting tactics and safety planning.

Other factors like the size and occupancy of a building, ventilation sources and interior furnishings, or the presence of automatic suppression and alarm systems affect fire dynamics, safety, and response, but they do not define the construction type itself.