The term platform framing is used by builders to refer to 2- or more story houses that are built 1 level at a time, meaning each floor becomes the platform upon which the next set of walls are built. The walls are positioned on the sub flooring.
Platform framing is the most common framing method for houses and small apartment buildings in the United States. The advantages far outweigh the disadvantages. An outdated from of construction called balloon framing is available, but platform framing is the preferred method.
The Advantages of Platform Framing
The first advantage to platform framing is that it uses shorter pieces of lumber. It also provides a solid floor surface upon which the carpenters may work. It offers higher durability and structural integrity; moreover, the hollow spaces allow for fire stops at each level.
The Disadvantages of Platform Framing
A disadvantage with platform framing is called vertical shrinkage. Because the floor is made of a thick layer of wood with the grain running horizontally, it may lead to vertical shrinking of the frame when the wood dries, causing stress on the finished surfaces.