Building construction types are divided between commercial and residential. There are some similarities in styles and regulations, but commercial construction uses more metal and masonry components and more fire resistant materials. Residential construction has a number of options, but the majority is wood-framed, built with walls formed of studs and plates (usually 2-by-4-inch lumber). Some masonry is used in residential buildings.
Commercial construction is divided by use and fire resistance. High-rise buildings and large residential units are Type I, the highest commercial class; schools and commercial buildings are Type II; and warehouses and similar buildings are Type III. Type I buildings have non-combustible and fire-resistant interior and exterior walls and other elements; Type II use non-combustible materials which may be fire resistant; and Type III uses masonry walls, but some combustible elements in other areas.
Most residential construction uses wood. The most common type is wood-framed, with walls, ceilings and roofs all built with lumber. Variations include post and beam, in which heavy posts support beams to carry the weight of the building and roof; and timber frame, which uses timbers rather than cut posts and beams in similar framing. Timber frames usually are fastened with mortise, tenon joints and wooden pegs, while post and beam uses nails, screws and metal supports. Wood framed has insulation between the studs and joists; the other types use structural insulated panels with thick foamboard between pressed wood.
Masonry is used in both residential and commercial construction. Variables are poured concrete walls, concrete or breeze block walls and brick. Block walls are common in warmer climates, such as Florida. A newer type of concrete wall, common now in cold regions, is insulated concrete forms. This utilises thick foamboard panels as forms for the concrete; the foamboard stays in place as insulation after the concrete walls set, producing thicker, better-insulated walls. Brick is used either as a structural wall or as facing on a wood-framed or block wall.
Steel is used in both commercial and residential construction, although it is more common in commercial. Skyscrapers and tall buildings are erected with big steel beams, but increasingly steel is used for internal framing, such as wall studs. Light gauge steel is used in residential construction, much like common wood framing, except that elements are fastened with screws rather than nails.