Expert diagrams of the two major types of wood-frame construction for house walls and roofs
Two basic methods are used for framing a house: platform and balloon-frame construction. Platform construction is much more common than balloon framing, though balloon framing was employed in many two-story houses before 1930.
With platform-frame construction, shown at right, walls sit on top of subflooring. Multistory houses are built one level at a time with each floor providing a platform for building the next series of walls.
With balloon-frame construction, shown below, studs run full height from mud sill to the top plate, to a maximum of 20 feet. This method was popular before the 1930s and is still used on occasion for stucco and other masonry-walled, two-story houses because such structures shrink and settle more uniformly than do platform structures. But balloon framing is more dangerous to erect because of its weight and height, and the long, straight wall studs required have grown increasingly expensive and difficult to find.
With both platform and balloon framing, wall studs and ceiling and floor joists occur every 16 or 24 inches, measured from center to center. These standardized layouts result in the least cutting and waste of floor, ceiling, and wall materials. Most older houses have 2-by-4 wall studs spaced 16 inches on center; many newer houses have 2-by-6 wall studs either 16 or 24 inches on center to make exterior walls stronger and create a larger cavity for wall insulation. For more about wall framing, see How to Build an Interior Wall.
Exterior wall sheathing adds rigidity to the structure and provides a flat base for siding, stucco, brick, stone, and other exterior wall finishes. Older homes have diagonal board sheathing—1/2-inch-thick boards nailed on the diagonal. Most newer homes have plywood or similar composite panel sheathing. For more about this, see Sheathing Exterior Walls.
Exterior roof sheathing serves the same purposes for roofing materials as wall sheathing does for walls. Most contemporary roof sheathing is either plywood or oriented-strand-board (OSB) panels; spaced wood sheathing is common for wood shingle roofs. For more about this, see Roof Construction Basics.