In platform-frame construction, how is the first floor constructed?

In platform-frame construction, the first floor is constructed as a platform, which is a defining characteristic of this building method. This approach involves constructing each floor separately, where the floor joists are placed on top of the exterior walls, and the walls of the second floor are built on top of these floor joists. This design provides several advantages, such as enhanced structural support and easier access for construction and future modifications.

The platform framing system is especially valued for its efficiency in materials usage and the speed with which construction can progress, since each "platform" can be framed, sheathed, and roofed independently. This method also allows for easier installation of plumbing, electrical systems, and insulation, as work can be done at floor level.

Other construction methods mentioned, like continuous frames, masonry walls, or steel girders, are not typical for platform-frame construction. In contrast, continuous framing involves an uninterrupted structure where components are tied together more rigidly. Masonry walls are primarily associated with different structural systems, such as load-bearing masonry construction. Steel girders are used in heavy construction and commercial buildings, rather than in the residential context typical of platform framing.