In platform construction, the floors and walls are built in sequential fashion, typically beginning with the first floor deck, which sits on the foundation. Floor joists are sheathed with sub-flooring, such as plywood or oriented strand board. Once the deck is sheathed, the walls are constructed on the “platform” and “tipped” into place. Wall sheathing may be attached to the stud prior to tipping the segment. Hence, the name “platform” derived from floor upon which exterior walls and interior partitions are constructed. The process continues with the installation of floor joists and decking on top of the walls, until the upper most wall is secured prior to placement of the roof framing.
In older style balloon-frame construction, exterior wall studs are continuous from the foundation to the roof. First floor joists and exterior wall studs both bear on the anchored sill. Second-floor joists bear on a minimum 1×4-inch ribbon strip, which has been let-in to the inside edges of exterior wall studs. In two-story buildings with brick or stone veneer exteriors, balloon framing reduces variations in settlement of framing and the masonry veneer. Balloon framing requires the installation of firestopping at the intersection floors and walls to prevent fire from moving freely throughout the wall cavity and into the attic.
Lumber which has been properly maintained in service can be expected to last for years. Building codes prescribe where certain applications require the use of preservative pressure treated wood. Preservative treated wood is typically used for exterior decks, sill plates, and post-frame buildings (pole barns). Fire retardant treated wood is used where enhanced flame spread characteristics are warranted. When treated in accordance with industry standards, the flame spread on lumber can be reduced to near zero. Fire retardant treated wood will burn when exposed to direct flame impingement, but it will retard the propagation of the flame along the product.