Framing, in construction, is the fitting together of pieces to give a structure support and shape. Framing materials are usually wood, engineered wood, or structural steel. The alternative to framed construction is generally called mass wall construction, where horizontal layers of stacked materials such as log building, masonry, rammed earth, adobe, etc. are used without framing.
Building framing is divided into two broad categories,heavy-frame construction (heavy framing) if the vertical supports are few and heavy such as in timber framing, pole building framing, or steel framing; or light-frame construction (light-framing) if the supports are more numerous and smaller, such as balloon, platform, or light-steel framing. Light-frame construction using standardized dimensional lumber has become the dominant construction method in North America and Australia due to the economy of the method; use of minimal structural material allows builders to enclose a large area at minimal cost while achieving a wide variety of architectural styles.
Modern light-frame structures usually gain strength from rigid panels (plywood and other plywood-like composites such as oriented strand board (OSB) used to form all or part of wall sections), but until recently carpenters employed various forms of diagonal bracing to stabilize walls. Diagonal bracing remains a vital interior part of many roof systems, and in-wall wind braces are required by building codes in many municipalities or by individual state laws in the United States. Special framed shear walls are becoming more common to help buildings meet the requirements of earthquake engineering and wind engineering.
Historically, people fitted naturally shaped wooden poles together as framework and then began using joints to connect the timbers, a method today called traditional timber framing’ or log framing. In the United States, timber framing was superseded by balloon framing beginning in the 1830s. Balloon framing makes use of many lightweight wall members called studs rather than fewer, heavier supports called posts; balloon framing components are nailed together rather than fitted using joinery. The studs in a balloon frame extend two stories from sill to plate. Platform framing superseded balloon framing and is the standard wooden framing method today. The name comes from each floor level being framed as a separate unit or platform.
Framed construction was rarely used in Scandinavia before the 20th century because of the abundant availability of wood, an abundance of cheap labour, and the superiority of the thermal insulation of logs; hence timber framing did not take off there first for unheated buildings such as farm buildings, outbuildings and summer villas, and for houses until the development of wall insulation.
Wall framing in house construction includes the vertical and horizontal members of exterior walls and interior partitions, both of bearing walls and non-bearing walls. These stick members, referred to as studs, wall plates and lintels (sometimes called headers), serve as a nailing base for all covering material and support the upper floor platforms, which provide the lateral strength along a wall. The platforms may be the boxed structure of a ceiling and roof, or the ceiling and floorjoists of the story above. In the building trades, the technique is variously referred to as stick and frame, stick and platform, or stick and box, as the sticks (studs) give the structure its vertical support, and the box-shaped floor sections with joists contained within length-long post and lintels (more commonly called headers), support the weight of whatever is above, including the next wall up and the roof above the top story. The platform also provides lateral support against wind and holds the stick walls true and square. Any lower platform supports the weight of the platforms and walls above the level of its component headers and joists.
There are three historically common methods of framing a house.
- Post and beam, which is now used predominantly in barn construction.
- Balloon framing using a technique suspending floors from the walls was common until the late 1940s, but since that time, platform framing has become the predominant form of house construction.
- Platform framing often forms wall sections horizontally on the sub-floor prior to erection, easing positioning of studs and increasing accuracy while cutting the necessary manpower. The top and bottom plates are end-nailed to each stud with two nails at least 3.25 in (83 mm) in length (16d or 16 penny nails). Studs are at least doubled (creating posts) at openings, the jack stud being cut to receive the lintels(headers) that are placed and end-nailed through the outer studs.
Wall sheathing, usually a plywood or other laminate, is usually applied to the framing prior to erection, thus eliminating the need to scaffold, and again increasing speed and cutting manpower needs and expenses. Some types of exterior sheathing, such as asphalt-impregnated fiberboard, plywood, oriented strand board and waferboard, will provide adequate bracing to resist lateral loads and keep the wall square. (Construction codes in most jurisdictions require a stiff plywood sheathing.) Others, such as rigid glass-fiber, asphalt-coated fiberboard, polystyrene or polyurethane board, will not. In this latter case, the wall should be reinforced with a diagonal wood or metal bracing inset into the studs. In jurisdictions subject to strong wind storms (hurricane countries, tornado alleys) local codes or state law will generally require both the diagonal wind braces and the stiff exterior sheathing regardless of the type and kind of outer weather resistant coverings.