<P> Wide sheets of steel deck can be used to cover the top of the steel frame as a "form" or corrugated mold, below a thick layer of concrete and steel reinforcing bars . Another popular alternative is a floor of precast concrete flooring units with some form of concrete topping . Often in office buildings, the final floor surface is provided by some form of raised flooring system with the void between the walking surface and the structural floor being used for cables and air handling ducts . </P> <P> The frame needs to be protected from fire because steel softens at high temperature and this can cause the building to partially collapse . In the case of the columns this is usually done by encasing it in some form of fire resistant structure such as masonry, concrete or plasterboard . The beams may be cased in concrete, plasterboard or sprayed with a coating to insulate it from the heat of the fire or it can be protected by a fire - resistant ceiling construction . Asbestos was a popular material for fireproofing steel structures up until the early 1970s, before the health risks of asbestos fibres were fully understood . </P> <P> The exterior "skin" of the building is anchored to the frame using a variety of construction techniques and following a huge variety of architectural styles . Bricks, stone, reinforced concrete, architectural glass, sheet metal and simply paint have been used to cover the frame to protect the steel from the weather . </P> <P> Thin sheets of galvanized steel can be cold formed into steel studs for use as a structural or non structural building material for both external and partition walls in both residential, commercial and industrial construction projects (pictured). The dimension of the room is established with horizontal track that is anchored to the floor and ceiling to outline each room . The vertical studs are arranged in the tracks, usually spaced 16" apart, and fastened at the top and bottom . </P>

When were metal studs first used in construction