Platform frame construction is distinguished by which characteristic?

Platform frame construction is primarily characterized by its method of building in layers, specifically one floor at a time, with the inclusion of fire stops between each floor. This construction technique involves using horizontal framing members that are built on top of each other, where each floor acts as a platform for the next. The incorporation of fire stops is critical as it helps to limit the vertical spread of fire from one level to another, enhancing the fire safety of the structure.

In this type of construction, the framing typically consists of studs that run from the foundation up to the roof, but the distinctive feature that sets it apart is that each floor is fully constructed before starting on the next, which not only facilitates fire resistance but also allows for easier construction techniques. This method contrasts with other types of construction where walls may be built continuously without such fire-stopping measures.

The options regarding noncombustible materials and heavy timber do not apply specifically to platform frame construction, as these materials can be used in various types of construction. Similarly, while walls extending from the basement to the roof can be a feature of some construction types, it is not a defining characteristic of platform framing. Hence, the focus on building one floor at a time with fire stops is what distinctly defines platform