What defines ordinary construction?

Ordinary construction is characterized by its use of non-combustible materials for structural support while also incorporating combustible elements like wood. This combination results in a building that is generally more fire-resistant than buildings constructed entirely of wood but less so than buildings made entirely of non-combustible materials.

In this context, the option indicating that exterior walls are masonry and the frame is wood aligns with the standard definition of ordinary construction. Masonry provides stability and fire resistance, while the wooden frame allows for easier construction and modification. This mix means that while the structure has some fire-resistive qualities, it can still sustain significant fire risk due to the wooden elements.

Other options describe construction types that do not match this blend of materials. For instance, steel and glass as exterior walls indicate a more modern approach with minimal combustible materials; masonry walls with a concrete foundation lean towards heavier construction typically associated with a fire-resistive category; and insulated walls with metal framing suggest a completely different construction style that emphasizes non-combustibility, which moves away from the ordinary construction classification. Thus, the response accurately encapsulates the essence of ordinary construction.